---
language: bc
contributors:
    - ["Btup"]
filename: learnbc.bc
---
```c
/*This is a multi-
line comment.*/
# This is also a (one-line) comment! (in GNU bc).

    /*1. Variables and control structures*/
num = 45 /*All variables save only doubles, and you cannot save
    string constants directly.*/
num = 45; /*You can choose to add a semicolon after
    every statement. This is optional.*/
/*Blocks are denoted using the {} operators(similar to C):*/
while(num < 50) {
    num += 1 /*equivalent to num=num+1.
    a = a op b is equivalent to a op= b.*/
}
/*And there are ++(increment) and --(decrement) operators.*/
/*There are 3 special variables:
scale: defines the scale of the double numbers.
ibase: defines the base of input.
obase: defines the base of output.*/
/*If clauses:*/
hour = read() /*Input a number*/

if(hour < 12) { /*Operators are exactly like C.*/
    print "Good morning\n" /*"print" outputs strings or variables
	separated by commas.*/
} else if(hour == 12) {
    print "Hello\n"
    /*Escaping sequences start with a \ in a string.
    In order to make the escaping sequences clearer, here
	is a simplified list of them that will work in bc:
    \b: backspace
    \c: carriage return
    \n: newline
    \t: tab
    \\: backslash*/
} else {
    /*Variables are global by default.*/
    thisIsGlobal = 5
    /*You can make a variable local. Use the "auto" keyword in a function.*/
}

/*Every variable is pre-set to 0.*/
num = blankVariable /*num is set to 0.*/

/*Like C, only 0 is falsy.*/
if(!num) {print "false\n"}

/*Unlike C, bc does not have the ?: operators. For example,
 this block of code will cause an error:
a = (num) ? 1 : 0
However, you can simulate one:*/
a = (num) && (1) || (0) /*&& is and, || is or*/

/*For loops*/
num = 0
for(i = 1; i <= 100; i++) {/*Similar to the C for loop.*/
    num += i
}

    /*2.Functions and Arrays*/
define fac(n) { /*define a function using define.*/
    if(n == 1 || n == 0) {
        return 1 /*return a value*/
    }
    return n * fac(n - 1) /*recursion is possible*/
}

/*Closures and anonymous functions are impossible.*/

num = fac(4) /*24*/

/*This is an example of local variables:*/
define x(n) {
    auto x
    x = 1
    return n + x
}
x(3) /*4*/
print x /*It turns out that x is not accessible out of the function.*/
/*Arrays are equivalent to the C array.*/
for(i = 0; i <= 3; i++) {
    a[i] = 1
}
/*Access it like this:*/
print a[0], " ", a[1], " ", a[2], " ", a[3], "\n"
quit /*Add this line of code to make sure
that your program exits. This line of code is optional.*/
```
Enjoy this simple calculator! (Or this programming language, to be exact.)

This whole program is written in GNU bc. To run it, use ```bc learnbc.bc```.
