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[Chapel/en] Update chapel.html.markdown (#3877)
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@ -13,7 +13,16 @@ as well as multi-kilocore supercomputers.
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More information and support can be found at the bottom of this document.
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You can refer to the official site for [latest version](https://chapel-lang.org/docs/master/primers/learnChapelInYMinutes.html) of this document.
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```chapel
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/*
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Learn Chapel in Y Minutes
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This primer will go over basic syntax and concepts in Chapel.
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Last sync with official page: Sun, 08 Mar 2020 08:05:53 +0000
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*/
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// Comments are C-family style
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// one line comment
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@ -21,34 +30,43 @@ More information and support can be found at the bottom of this document.
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multi-line comment
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*/
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// Basic printing
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/*
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Basic printing
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*/
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write("Hello, ");
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writeln("World!");
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// write and writeln can take a list of things to print.
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// ``write`` and ``writeln`` can take a list of things to print.
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// Each thing is printed right next to the others, so include your spacing!
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writeln("There are ", 3, " commas (\",\") in this line of code");
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// Different output channels:
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use IO; // Required for accessing the alternative output channels
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stdout.writeln("This goes to standard output, just like plain writeln() does");
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stderr.writeln("This goes to standard error");
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/*
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Variables
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*/
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// Variables don't have to be explicitly typed as long as
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// the compiler can figure out the type that it will hold.
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// 10 is an int, so myVar is implicitly an int
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// 10 is an ``int``, so ``myVar`` is implicitly an ``int``
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var myVar = 10;
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myVar = -10;
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var mySecondVar = myVar;
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// var anError; would be a compile-time error.
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// ``var anError;`` would be a compile-time error.
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// We can (and should) explicitly type things.
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var myThirdVar: real;
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var myFourthVar: real = -1.234;
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myThirdVar = myFourthVar;
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// Types
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/*
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Types
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*/
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// There are a number of basic types.
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var myInt: int = -1000; // Signed ints
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@ -75,30 +93,34 @@ type RGBColor = 3*chroma; // Type representing a full color
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var black: RGBColor = (0,0,0);
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var white: RGBColor = (255, 255, 255);
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// Constants and Parameters
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/*
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Constants and Parameters
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*/
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// A const is a constant, and cannot be changed after set in runtime.
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// A ``const`` is a constant, and cannot be changed after set in runtime.
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const almostPi: real = 22.0/7.0;
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// A param is a constant whose value must be known statically at
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// A ``param`` is a constant whose value must be known statically at
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// compile-time.
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param compileTimeConst: int = 16;
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// The config modifier allows values to be set at the command line.
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// Set with --varCmdLineArg=Value or --varCmdLineArg Value at runtime.
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// The ``config`` modifier allows values to be set at the command line.
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// Set with ``--varCmdLineArg=Value`` or ``--varCmdLineArg Value`` at runtime.
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config var varCmdLineArg: int = -123;
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config const constCmdLineArg: int = 777;
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// config param can be set at compile-time.
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// Set with --set paramCmdLineArg=value at compile-time.
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// ``config param`` can be set at compile-time.
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// Set with ``--set paramCmdLineArg=value`` at compile-time.
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config param paramCmdLineArg: bool = false;
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writeln(varCmdLineArg, ", ", constCmdLineArg, ", ", paramCmdLineArg);
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// References
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/*
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References
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*/
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// ref operates much like a reference in C++. In Chapel, a ref cannot
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// ``ref`` operates much like a reference in C++. In Chapel, a ``ref`` cannot
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// be made to alias a variable other than the variable it is initialized with.
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// Here, refToActual refers to actual.
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// Here, ``refToActual`` refers to ``actual``.
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var actual = 10;
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ref refToActual = actual;
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writeln(actual, " == ", refToActual); // prints the same value
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@ -107,7 +129,9 @@ writeln(actual, " == ", refToActual); // prints the same value
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refToActual = 99999999; // modify what refToActual refers to (which is actual)
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writeln(actual, " == ", refToActual); // prints the same value
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// Operators
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/*
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Operators
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*/
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// Math operators:
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var a: int, thisInt = 1234, thatInt = 5678;
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@ -146,7 +170,7 @@ a <<= 3; // Left-bit-shift-equals (a = a << 10;)
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// Unlike other C family languages, there are no
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// pre/post-increment/decrement operators, such as:
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//
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// ++j, --j, j++, j--
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// ``++j``, ``--j``, ``j++``, ``j--``
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// Swap operator:
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var old_this = thisInt;
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@ -156,7 +180,9 @@ writeln((old_this == thatInt) && (old_that == thisInt));
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// Operator overloads can also be defined, as we'll see with procedures.
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// Tuples
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/*
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Tuples
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*/
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// Tuples can be of the same type or different types.
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var sameTup: 2*int = (10, -1);
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@ -179,16 +205,18 @@ writeln(diffTup == (tupInt, tupReal, tupCplx));
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// They are also useful for writing a list of variables, as is common in debugging.
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writeln((a,b,thisInt,thatInt,thisBool,thatBool));
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// Control Flow
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/*
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Control Flow
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*/
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// if - then - else works just like any other C-family language.
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// ``if`` - ``then`` - ``else`` works just like any other C-family language.
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if 10 < 100 then
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writeln("All is well");
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if -1 < 1 then
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writeln("Continuing to believe reality");
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else
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writeln("Send mathematician, something is wrong");
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writeln("Send mathematician, something's wrong");
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// You can use parentheses if you prefer.
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if (10 > 100) {
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@ -209,11 +237,11 @@ if a % 3 == 0 {
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writeln(b, " is divided by 3 with a remainder of 2.");
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}
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// Ternary: if - then - else in a statement.
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// Ternary: ``if`` - ``then`` - ``else`` in a statement.
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var maximum = if thisInt < thatInt then thatInt else thisInt;
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// select statements are much like switch statements in other languages.
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// However, select statements do not cascade like in C or Java.
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// ``select`` statements are much like switch statements in other languages.
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// However, ``select`` statements don't cascade like in C or Java.
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var inputOption = "anOption";
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select inputOption {
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when "anOption" do writeln("Chose 'anOption'");
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@ -223,11 +251,11 @@ select inputOption {
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}
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otherwise {
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writeln("Any other Input");
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writeln("the otherwise case does not need a do if the body is one line");
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writeln("the otherwise case doesn't need a do if the body is one line");
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}
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}
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// while and do-while loops also behave like their C counterparts.
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// ``while`` and ``do``-``while`` loops also behave like their C counterparts.
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var j: int = 1;
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var jSum: int = 0;
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while (j <= 1000) {
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@ -242,8 +270,8 @@ do {
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} while (j <= 10000);
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writeln(jSum);
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// for loops are much like those in Python in that they iterate over a
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// range. Ranges (like the 1..10 expression below) are a first-class object
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// ``for`` loops are much like those in python in that they iterate over a
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// range. Ranges (like the ``1..10`` expression below) are a first-class object
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// in Chapel, and as such can be stored in variables.
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for i in 1..10 do write(i, ", ");
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writeln();
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@ -261,7 +289,9 @@ for x in 1..10 {
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writeln();
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}
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// Ranges and Domains
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/*
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Ranges and Domains
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*/
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// For-loops and arrays both use ranges and domains to define an index set that
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// can be iterated over. Ranges are single dimensional integer indices, while
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@ -277,17 +307,18 @@ var rangeEmpty: range = 100..-100; // this is valid but contains no indices
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var range1toInf: range(boundedType=BoundedRangeType.boundedLow) = 1.. ; // 1, 2, 3, 4, 5, ...
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var rangeNegInfTo1 = ..1; // ..., -4, -3, -2, -1, 0, 1
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// Ranges can be strided (and reversed) using the by operator.
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// Ranges can be strided (and reversed) using the ``by`` operator.
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var range2to10by2: range(stridable=true) = 2..10 by 2; // 2, 4, 6, 8, 10
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var reverse2to10by2 = 2..10 by -2; // 10, 8, 6, 4, 2
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var trapRange = 10..1 by -1; // Do not be fooled, this is still an empty range
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writeln("Size of range ", trapRange, " = ", trapRange.length);
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writeln("Size of range '", trapRange, "' = ", trapRange.size);
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// Note: range(boundedType= ...) and range(stridable= ...) are only
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// Note: ``range(boundedType= ...)`` and ``range(stridable= ...)`` are only
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// necessary if we explicitly type the variable.
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// The end point of a range can be determined using the count (#) operator.
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// The end point of a range can be computed by specifying the total size
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// of the range using the count (``#``) operator.
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var rangeCount: range = -5..#12; // range from -5 to 6
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// Operators can be mixed.
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@ -297,8 +328,8 @@ writeln(rangeCountBy);
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// Properties of the range can be queried.
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// In this example, printing the first index, last index, number of indices,
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// stride, and if 2 is include in the range.
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writeln((rangeCountBy.first, rangeCountBy.last, rangeCountBy.length,
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rangeCountBy.stride, rangeCountBy.member(2)));
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writeln((rangeCountBy.first, rangeCountBy.last, rangeCountBy.size,
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rangeCountBy.stride, rangeCountBy.contains(2)));
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for i in rangeCountBy {
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write(i, if i == rangeCountBy.last then "\n" else ", ");
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@ -322,7 +353,7 @@ for idx in twoDimensions do
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write(idx, ", ");
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writeln();
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// These tuples can also be deconstructed.
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// These tuples can also be destructured.
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for (x,y) in twoDimensions {
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write("(", x, ", ", y, ")", ", ");
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}
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@ -352,7 +383,9 @@ var domainB = {-5..5, 1..10};
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var domainC = domainA[domainB];
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writeln((domainA, domainB, domainC));
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// Arrays
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/*
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Arrays
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*/
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// Arrays are similar to those of other languages.
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// Their sizes are defined using domains that represent their indices.
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@ -364,9 +397,9 @@ for i in 1..10 do
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intArray[i] = -i;
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writeln(intArray);
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// We cannot access intArray[0] because it exists outside
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// of the index set, {1..10}, we defined it to have.
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// intArray[11] is illegal for the same reason.
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// We cannot access ``intArray[0]`` because it exists outside
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// of the index set, ``{1..10}``, we defined it to have.
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// ``intArray[11]`` is illegal for the same reason.
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var realDomain: domain(2) = {1..5,1..7};
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var realArray: [realDomain] real;
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var realArray2: [1..5,1..7] real; // equivalent
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@ -396,9 +429,9 @@ for value in realArray {
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writeln(rSum, "\n", realArray);
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// Associative arrays (dictionaries) can be created using associative domains.
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var dictDomain: domain(string) = { "one", "two" };
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var dict: [dictDomain] int = ["one" => 1, "two" => 2];
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dict["three"] = 3; // Adds 'three' to 'dictDomain' implicitly
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var dictDomain: domain(string) = { "one", "two", "three"};
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var dict: [dictDomain] int = ["one" => 1, "two" => 2, "three" => 3];
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for key in dictDomain.sorted() do
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writeln(dict[key]);
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@ -407,9 +440,9 @@ for key in dictDomain.sorted() do
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var thisArray : [0..5] int = [0,1,2,3,4,5];
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var thatArray : [0..5] int;
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// First, simply assign one to the other. This copies thisArray into
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// thatArray, instead of just creating a reference. Therefore, modifying
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// thisArray does not also modify thatArray.
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// First, simply assign one to the other. This copies ``thisArray`` into
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// ``thatArray``, instead of just creating a reference. Therefore, modifying
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// ``thisArray`` does not also modify ``thatArray``.
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thatArray = thisArray;
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thatArray[1] = -1;
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@ -425,7 +458,7 @@ var thisPlusThat = thisArray + thatArray;
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writeln(thisPlusThat);
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// Moving on, arrays and loops can also be expressions, where the loop
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// body expression is the result of each iteration.
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// body's expression is the result of each iteration.
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var arrayFromLoop = for i in 1..10 do i;
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writeln(arrayFromLoop);
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@ -435,14 +468,16 @@ var evensOrFives = for i in 1..10 do if (i % 2 == 0 || i % 5 == 0) then i;
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writeln(arrayFromLoop);
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// Array expressions can also be written with a bracket notation.
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// Note: this syntax uses the forall parallel concept discussed later.
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// Note: this syntax uses the ``forall`` parallel concept discussed later.
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var evensOrFivesAgain = [i in 1..10] if (i % 2 == 0 || i % 5 == 0) then i;
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// They can also be written over the values of the array.
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arrayFromLoop = [value in arrayFromLoop] value + 1;
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// Procedures
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/*
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Procedures
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*/
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// Chapel procedures have similar syntax functions in other languages.
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proc fibonacci(n : int) : int {
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@ -482,10 +517,10 @@ writeln(defaultsProc(x=11));
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writeln(defaultsProc(x=12, y=5.432));
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writeln(defaultsProc(y=9.876, x=13));
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// The ? operator is called the query operator, and is used to take
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// The ``?`` operator is called the query operator, and is used to take
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// undetermined values like tuple or array sizes and generic types.
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// For example, taking arrays as parameters. The query operator is used to
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// determine the domain of A. This is uesful for defining the return type,
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// determine the domain of ``A``. This is useful for defining the return type,
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// though it's not required.
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proc invertArray(A: [?D] int): [D] int{
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for a in A do a = -a;
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@ -509,7 +544,7 @@ genericProc(1, 2);
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genericProc(1.2, 2.3);
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genericProc(1.0+2.0i, 3.0+4.0i);
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// We can also enforce a form of polymorphism with the where clause
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// We can also enforce a form of polymorphism with the ``where`` clause
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// This allows the compiler to decide which function to use.
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// Note: That means that all information needs to be known at compile-time.
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// The param modifier on the arg is used to enforce this constraint.
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@ -526,13 +561,13 @@ proc whereProc(param N : int): void
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whereProc(10);
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whereProc(-1);
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// whereProc(0) would result in a compiler error because there
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// are no functions that satisfy the where clause's condition.
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// We could have defined a whereProc without a where clause
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// ``whereProc(0)`` would result in a compiler error because there
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// are no functions that satisfy the ``where`` clause's condition.
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// We could have defined a ``whereProc`` without a ``where`` clause
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// that would then have served as a catch all for all the other cases
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// (of which there is only one).
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// where clauses can also be used to constrain based on argument type.
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// ``where`` clauses can also be used to constrain based on argument type.
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proc whereType(x: ?t) where t == int {
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writeln("Inside 'int' version of 'whereType': ", x);
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}
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@ -544,7 +579,9 @@ proc whereType(x: ?t) {
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whereType(42);
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whereType("hello");
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// Intents
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/*
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Intents
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*/
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/* Intent modifiers on the arguments convey how those arguments are passed to the procedure.
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@ -571,7 +608,7 @@ intentsProc(inVar, outVar, inoutVar, refVar);
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writeln("Outside After: ", (inVar, outVar, inoutVar, refVar));
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// Similarly, we can define intents on the return type.
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// refElement returns a reference to an element of array.
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// ``refElement`` returns a reference to an element of array.
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// This makes more practical sense for class methods where references to
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// elements in a data-structure are returned via a method or iterator.
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proc refElement(array : [?D] ?T, idx) ref : T {
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@ -586,14 +623,16 @@ refToElem = -2; // modify reference which modifies actual value in array
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writeln(refToElem);
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writeln(myChangingArray);
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// Operator Definitions
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/*
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Operator Definitions
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*/
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// Chapel allows for operators to be overloaded.
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// We can define the unary operators:
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// + - ! ~
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// ``+ - ! ~``
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// and the binary operators:
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// + - * / % ** == <= >= < > << >> & | ˆ by
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// += -= *= /= %= **= &= |= ˆ= <<= >>= <=>
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// ``+ - * / % ** == <= >= < > << >> & | ˆ by``
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// ``+= -= *= /= %= **= &= |= ˆ= <<= >>= <=>``
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// Boolean exclusive or operator.
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proc ^(left : bool, right : bool): bool {
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@ -605,25 +644,28 @@ writeln(false ^ true);
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writeln(true ^ false);
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writeln(false ^ false);
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// Define a * operator on any two types that returns a tuple of those types.
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// Define a ``*`` operator on any two types that returns a tuple of those types.
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proc *(left : ?ltype, right : ?rtype): (ltype, rtype) {
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writeln("\tIn our '*' overload!");
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return (left, right);
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}
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writeln(1 * "a"); // Uses our * operator.
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writeln(1 * 2); // Uses the default * operator.
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writeln(1 * "a"); // Uses our ``*`` operator.
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writeln(1 * 2); // Uses the default ``*`` operator.
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|
||||
// Note: You could break everything if you get careless with your overloads.
|
||||
// This here will break everything. Don't do it.
|
||||
|
||||
/*
|
||||
|
||||
proc +(left: int, right: int): int {
|
||||
return left - right;
|
||||
}
|
||||
*/
|
||||
|
||||
// Iterators
|
||||
/*
|
||||
Iterators
|
||||
*/
|
||||
|
||||
// Iterators are sisters to the procedure, and almost everything about
|
||||
// procedures also applies to iterators. However, instead of returning a single
|
||||
@ -656,7 +698,7 @@ for i in absolutelyNothing(10) {
|
||||
}
|
||||
|
||||
// We can zipper together two or more iterators (who have the same number
|
||||
// of iterations) using zip() to create a single zipped iterator, where each
|
||||
// of iterations) using ``zip()`` to create a single zipped iterator, where each
|
||||
// iteration of the zipped iterator yields a tuple of one value yielded
|
||||
// from each iterator.
|
||||
for (positive, negative) in zip(1..5, -5..-1) do
|
||||
@ -683,8 +725,7 @@ for (i, j) in zip(toThisArray.domain, -100..#5) {
|
||||
}
|
||||
writeln(toThisArray);
|
||||
|
||||
// This is very important in understanding why this statement exhibits a
|
||||
// runtime error.
|
||||
// This is very important in understanding why this statement exhibits a runtime error.
|
||||
|
||||
/*
|
||||
var iterArray : [1..10] int = [i in 1..10] if (i % 2 == 1) then i;
|
||||
@ -695,8 +736,9 @@ writeln(toThisArray);
|
||||
// Because iterators can yield nothing, that iterator yields a different number
|
||||
// of things than the domain of the array or loop, which is not allowed.
|
||||
|
||||
// Classes
|
||||
|
||||
/*
|
||||
Classes
|
||||
*/
|
||||
// Classes are similar to those in C++ and Java, allocated on the heap.
|
||||
class MyClass {
|
||||
|
||||
@ -704,13 +746,16 @@ class MyClass {
|
||||
var memberInt : int;
|
||||
var memberBool : bool = true;
|
||||
|
||||
// Explicitly defined initializer.
|
||||
// We also get the compiler-generated initializer, with one argument per field.
|
||||
// Note that soon there will be no compiler-generated initializer when we
|
||||
// define any initializer(s) explicitly.
|
||||
proc init(val : real) {
|
||||
this.memberInt = ceil(val): int;
|
||||
}
|
||||
// By default, any class that doesn't define an initializer gets a
|
||||
// compiler-generated initializer, with one argument per field and
|
||||
// the field's initial value as the argument's default value.
|
||||
// Alternatively, the user can define initializers manually as shown
|
||||
// in the following commented-out routine:
|
||||
//
|
||||
/* // proc init(val : real) {
|
||||
// this.memberInt = ceil(val): int;
|
||||
// }
|
||||
*/
|
||||
|
||||
// Explicitly defined deinitializer.
|
||||
// If we did not write one, we would get the compiler-generated deinitializer,
|
||||
@ -738,36 +783,44 @@ class MyClass {
|
||||
} // end MyClass
|
||||
|
||||
// Call compiler-generated initializer, using default value for memberBool.
|
||||
var myObject = new MyClass(10);
|
||||
myObject = new MyClass(memberInt = 10); // Equivalent
|
||||
{
|
||||
var myObject = new owned MyClass(10);
|
||||
myObject = new owned MyClass(memberInt = 10); // Equivalent
|
||||
writeln(myObject.getMemberInt());
|
||||
|
||||
// Same, but provide a memberBool value explicitly.
|
||||
var myDiffObject = new MyClass(-1, true);
|
||||
myDiffObject = new MyClass(memberInt = -1,
|
||||
var myDiffObject = new owned MyClass(-1, true);
|
||||
myDiffObject = new owned MyClass(memberInt = -1,
|
||||
memberBool = true); // Equivalent
|
||||
writeln(myDiffObject);
|
||||
|
||||
// Call the initializer we wrote.
|
||||
var myOtherObject = new MyClass(1.95);
|
||||
myOtherObject = new MyClass(val = 1.95); // Equivalent
|
||||
writeln(myOtherObject.getMemberInt());
|
||||
// Similar, but rely on the default value of memberInt, passing in memberBool.
|
||||
var myThirdObject = new owned MyClass(memberBool = true);
|
||||
writeln(myThirdObject);
|
||||
|
||||
// If the user-defined initializer above had been uncommented, we could
|
||||
// make the following calls:
|
||||
//
|
||||
/* // var myOtherObject = new MyClass(1.95);
|
||||
// myOtherObject = new MyClass(val = 1.95);
|
||||
// writeln(myOtherObject.getMemberInt());
|
||||
*/
|
||||
|
||||
// We can define an operator on our class as well, but
|
||||
// the definition has to be outside the class definition.
|
||||
proc +(A : MyClass, B : MyClass) : MyClass {
|
||||
return new MyClass(memberInt = A.getMemberInt() + B.getMemberInt(),
|
||||
proc +(A : MyClass, B : MyClass) : owned MyClass {
|
||||
return
|
||||
new owned MyClass(memberInt = A.getMemberInt() + B.getMemberInt(),
|
||||
memberBool = A.getMemberBool() || B.getMemberBool());
|
||||
}
|
||||
|
||||
var plusObject = myObject + myDiffObject;
|
||||
writeln(plusObject);
|
||||
|
||||
// Destruction.
|
||||
delete myObject;
|
||||
delete myDiffObject;
|
||||
delete myOtherObject;
|
||||
delete plusObject;
|
||||
// Destruction of an object: calls the deinit() routine and frees its memory.
|
||||
// ``unmanaged`` variables should have ``delete`` called on them.
|
||||
// ``owned`` variables are destroyed when they go out of scope.
|
||||
}
|
||||
|
||||
// Classes can inherit from one or more parent classes
|
||||
class MyChildClass : MyClass {
|
||||
@ -780,42 +833,46 @@ class GenericClass {
|
||||
var classDomain: domain(1);
|
||||
var classArray: [classDomain] classType;
|
||||
|
||||
// Explicit constructor.
|
||||
proc GenericClass(type classType, elements : int) {
|
||||
this.classDomain = {1..#elements};
|
||||
// Explicit initializer.
|
||||
proc init(type classType, elements : int) {
|
||||
this.classType = classType;
|
||||
this.classDomain = {1..elements};
|
||||
// all generic and const fields must be initialized in "phase 1" prior
|
||||
// to a call to the superclass initializer.
|
||||
}
|
||||
|
||||
// Copy constructor.
|
||||
// Note: We still have to put the type as an argument, but we can
|
||||
// default to the type of the other object using the query (?) operator.
|
||||
// Further, we can take advantage of this to allow our copy constructor
|
||||
// to copy classes of different types and cast on the fly.
|
||||
proc GenericClass(other : GenericClass(?otherType),
|
||||
type classType = otherType) {
|
||||
// Copy-style initializer.
|
||||
// Note: We include a type argument whose default is the type of the first
|
||||
// argument. This lets our initializer copy classes of different
|
||||
// types and cast on the fly.
|
||||
proc init(other : GenericClass(?),
|
||||
type classType = other.classType) {
|
||||
this.classType = classType;
|
||||
this.classDomain = other.classDomain;
|
||||
// Copy and cast
|
||||
for idx in this.classDomain do this[idx] = other[idx] : classType;
|
||||
this.classArray = for o in other do o: classType; // copy and cast
|
||||
}
|
||||
|
||||
// Define bracket notation on a GenericClass
|
||||
// object so it can behave like a normal array
|
||||
// i.e. objVar[i] or objVar(i)
|
||||
// i.e. ``objVar[i]`` or ``objVar(i)``
|
||||
proc this(i : int) ref : classType {
|
||||
return this.classArray[i];
|
||||
}
|
||||
|
||||
// Define an implicit iterator for the class
|
||||
// to yield values from the array to a loop
|
||||
// i.e. for i in objVar do ...
|
||||
// i.e. ``for i in objVar do ...``
|
||||
iter these() ref : classType {
|
||||
for i in this.classDomain do
|
||||
yield this[i];
|
||||
}
|
||||
} // end GenericClass
|
||||
|
||||
// Allocate an owned instance of our class
|
||||
var realList = new owned GenericClass(real, 10);
|
||||
|
||||
// We can assign to the member array of the object using the bracket
|
||||
// notation that we defined.
|
||||
var realList = new GenericClass(real, 10);
|
||||
for i in realList.classDomain do realList[i] = i + 1.0;
|
||||
|
||||
// We can iterate over the values in our list with the iterator
|
||||
@ -823,23 +880,25 @@ for i in realList.classDomain do realList[i] = i + 1.0;
|
||||
for value in realList do write(value, ", ");
|
||||
writeln();
|
||||
|
||||
// Make a copy of realList using the copy constructor.
|
||||
var copyList = new GenericClass(realList);
|
||||
// Make a copy of realList using the copy initializer.
|
||||
var copyList = new owned GenericClass(realList);
|
||||
for value in copyList do write(value, ", ");
|
||||
writeln();
|
||||
|
||||
// Make a copy of realList and change the type, also using the copy constructor.
|
||||
var copyNewTypeList = new GenericClass(realList, int);
|
||||
// Make a copy of realList and change the type, also using the copy initializer.
|
||||
var copyNewTypeList = new owned GenericClass(realList, int);
|
||||
for value in copyNewTypeList do write(value, ", ");
|
||||
writeln();
|
||||
|
||||
|
||||
// Modules
|
||||
/*
|
||||
Modules
|
||||
*/
|
||||
|
||||
// Modules are Chapel's way of managing name spaces.
|
||||
// The files containing these modules do not need to be named after the modules
|
||||
// (as in Java), but files implicitly name modules.
|
||||
// For example, this file implicitly names the learnChapelInYMinutes module
|
||||
// For example, this file implicitly names the ``learnChapelInYMinutes`` module
|
||||
|
||||
module OurModule {
|
||||
|
||||
@ -870,21 +929,23 @@ module OurModule {
|
||||
}
|
||||
} // end OurModule
|
||||
|
||||
// Using OurModule also uses all the modules it uses.
|
||||
// Since OurModule uses Time, we also use Time.
|
||||
// Using ``OurModule`` also uses all the modules it uses.
|
||||
// Since ``OurModule`` uses ``Time``, we also use ``Time``.
|
||||
use OurModule;
|
||||
|
||||
// At this point we have not used ChildModule or SiblingModule so
|
||||
// their symbols (i.e. foo) are not available to us. However, the module
|
||||
// names are available, and we can explicitly call foo() through them.
|
||||
// At this point we have not used ``ChildModule`` or ``SiblingModule`` so
|
||||
// their symbols (i.e. ``foo``) are not available to us. However, the module
|
||||
// names are available, and we can explicitly call ``foo()`` through them.
|
||||
SiblingModule.foo();
|
||||
OurModule.ChildModule.foo();
|
||||
|
||||
// Now we use ChildModule, enabling unqualified calls.
|
||||
// Now we use ``ChildModule``, enabling unqualified calls.
|
||||
use ChildModule;
|
||||
foo();
|
||||
|
||||
// Parallelism
|
||||
/*
|
||||
Parallelism
|
||||
*/
|
||||
|
||||
// In other languages, parallelism is typically done with
|
||||
// complicated libraries and strange class structure hierarchies.
|
||||
@ -894,9 +955,9 @@ foo();
|
||||
// executed.
|
||||
proc main() {
|
||||
|
||||
// A begin statement will spin the body of that statement off
|
||||
// A ``begin`` statement will spin the body of that statement off
|
||||
// into one new task.
|
||||
// A sync statement will ensure that the progress of the main
|
||||
// A ``sync`` statement will ensure that the progress of the main
|
||||
// task will not progress until the children have synced back up.
|
||||
|
||||
sync {
|
||||
@ -913,7 +974,7 @@ proc main() {
|
||||
writeln("fibonacci(",n,") = ", fibonacci(n));
|
||||
}
|
||||
|
||||
// A cobegin statement will spin each statement of the body into one new
|
||||
// A ``cobegin`` statement will spin each statement of the body into one new
|
||||
// task. Notice here that the prints from each statement may happen in any
|
||||
// order.
|
||||
cobegin {
|
||||
@ -929,17 +990,17 @@ proc main() {
|
||||
}
|
||||
}
|
||||
|
||||
// A coforall loop will create a new task for EACH iteration.
|
||||
// A ``coforall`` loop will create a new task for EACH iteration.
|
||||
// Again we see that prints happen in any order.
|
||||
// NOTE: coforall should be used only for creating tasks!
|
||||
// NOTE: ``coforall`` should be used only for creating tasks!
|
||||
// Using it to iterating over a structure is very a bad idea!
|
||||
var num_tasks = 10; // Number of tasks we want
|
||||
coforall taskID in 1..#num_tasks {
|
||||
coforall taskID in 1..num_tasks {
|
||||
writeln("Hello from task# ", taskID);
|
||||
}
|
||||
|
||||
// forall loops are another parallel loop, but only create a smaller number
|
||||
// of tasks, specifically --dataParTasksPerLocale= number of tasks.
|
||||
// ``forall`` loops are another parallel loop, but only create a smaller number
|
||||
// of tasks, specifically ``--dataParTasksPerLocale=`` number of tasks.
|
||||
forall i in 1..100 {
|
||||
write(i, ", ");
|
||||
}
|
||||
@ -951,10 +1012,10 @@ proc main() {
|
||||
// (1..3, 4..6, or 7..9) doing that chunk serially, but each task happens
|
||||
// in parallel. Your results may depend on your machine and configuration
|
||||
|
||||
// For both the forall and coforall loops, the execution of the
|
||||
// For both the ``forall`` and ``coforall`` loops, the execution of the
|
||||
// parent task will not continue until all the children sync up.
|
||||
|
||||
// forall loops are particularly useful for parallel iteration over arrays.
|
||||
// ``forall`` loops are particularly useful for parallel iteration over arrays.
|
||||
// Lets run an experiment to see how much faster a parallel loop is
|
||||
use Time; // Import the Time module to use Timer objects
|
||||
var timer: Timer;
|
||||
@ -982,14 +1043,14 @@ proc main() {
|
||||
// the parallel loop went faster than the serial loop.
|
||||
|
||||
// The bracket style loop-expression described
|
||||
// much earlier implicitly uses a forall loop.
|
||||
// much earlier implicitly uses a ``forall`` loop.
|
||||
[val in myBigArray] val = 1 / val; // Parallel operation
|
||||
|
||||
// Atomic variables, common to many languages, are ones whose operations
|
||||
// occur uninterrupted. Multiple threads can therefore modify atomic
|
||||
// variables and can know that their values are safe.
|
||||
// Chapel atomic variables can be of type bool, int,
|
||||
// uint, and real.
|
||||
// Chapel atomic variables can be of type ``bool``, ``int``,
|
||||
// ``uint``, and ``real``.
|
||||
var uranium: atomic int;
|
||||
uranium.write(238); // atomically write a variable
|
||||
writeln(uranium.read()); // atomically read a variable
|
||||
@ -1003,7 +1064,7 @@ proc main() {
|
||||
writeln("uranium was ", was, " but is now ", replaceWith);
|
||||
|
||||
var isEqualTo = 235;
|
||||
if uranium.compareExchange(isEqualTo, replaceWith) {
|
||||
if uranium.compareAndSwap(isEqualTo, replaceWith) {
|
||||
writeln("uranium was equal to ", isEqualTo,
|
||||
" so replaced value with ", replaceWith);
|
||||
} else {
|
||||
@ -1025,7 +1086,7 @@ proc main() {
|
||||
}
|
||||
}
|
||||
|
||||
// sync variables have two states: empty and full.
|
||||
// ``sync`` variables have two states: empty and full.
|
||||
// If you read an empty variable or write a full variable, you are waited
|
||||
// until the variable is full or empty again.
|
||||
var someSyncVar$: sync int; // varName$ is a convention not a law.
|
||||
@ -1043,9 +1104,8 @@ proc main() {
|
||||
}
|
||||
}
|
||||
|
||||
// single vars can only be written once. A read on an unwritten single
|
||||
// results in a wait, but when the variable has a value it can be read
|
||||
// indefinitely.
|
||||
// ``single`` vars can only be written once. A read on an unwritten ``single``
|
||||
// results in a wait, but when the variable has a value it can be read indefinitely.
|
||||
var someSingleVar$: single int; // varName$ is a convention not a law.
|
||||
sync {
|
||||
begin { // Reader task
|
||||
@ -1063,7 +1123,7 @@ proc main() {
|
||||
}
|
||||
}
|
||||
|
||||
// Here's an example using atomics and a sync variable to create a
|
||||
// Here's an example using atomics and a ``sync`` variable to create a
|
||||
// count-down mutex (also known as a multiplexer).
|
||||
var count: atomic int; // our counter
|
||||
var lock$: sync bool; // the mutex lock
|
||||
@ -1074,7 +1134,7 @@ proc main() {
|
||||
// (full:unlocked / empty:locked)
|
||||
// Also, writeXF() fills (F) the sync var regardless of its state (X)
|
||||
|
||||
coforall task in 1..#5 { // Generate tasks
|
||||
coforall task in 1..5 { // Generate tasks
|
||||
// Create a barrier
|
||||
do {
|
||||
lock$; // Read lock$ (wait)
|
||||
@ -1091,7 +1151,7 @@ proc main() {
|
||||
lock$.writeXF(true); // Set lock$ to full (signal)
|
||||
}
|
||||
|
||||
// We can define the operations + * & | ^ && || min max minloc maxloc
|
||||
// We can define the operations ``+ * & | ^ && || min max minloc maxloc``
|
||||
// over an entire array using scans and reductions.
|
||||
// Reductions apply the operation over the entire array and
|
||||
// result in a scalar value.
|
||||
@ -1099,7 +1159,7 @@ proc main() {
|
||||
var sumOfValues = + reduce listOfValues;
|
||||
var maxValue = max reduce listOfValues; // 'max' give just max value
|
||||
|
||||
// maxloc gives max value and index of the max value.
|
||||
// ``maxloc`` gives max value and index of the max value.
|
||||
// Note: We have to zip the array and domain together with the zip iterator.
|
||||
var (theMaxValue, idxOfMax) = maxloc reduce zip(listOfValues,
|
||||
listOfValues.domain);
|
||||
@ -1108,7 +1168,7 @@ proc main() {
|
||||
|
||||
// Scans apply the operation incrementally and return an array with the
|
||||
// values of the operation at that index as it progressed through the
|
||||
// array from array.domain.low to array.domain.high.
|
||||
// array from ``array.domain.low`` to ``array.domain.high``.
|
||||
var runningSumOfValues = + scan listOfValues;
|
||||
var maxScan = max scan listOfValues;
|
||||
writeln(runningSumOfValues);
|
||||
|
||||
Loading…
Reference in New Issue
Block a user