mirror of
https://github.com/adambard/learnxinyminutes-docs.git
synced 2024-12-23 17:41:41 +00:00
Remove multiline comments
Julia introduced "#=" and "=#" as the delimiters for multiline comments.
This commit is contained in:
Guillermo Garza
parent
a045c44c98
commit
9395900afd
@ -21,58 +21,58 @@ This is based on the current development version of Julia, as of October 18th, 2
|
||||
# Everything in Julia is a expression.
|
||||
|
||||
# There are several basic types of numbers.
|
||||
3 #=> 3 (Int64)
|
||||
3.2 #=> 3.2 (Float64)
|
||||
2 + 1im #=> 2 + 1im (Complex{Int64})
|
||||
2//3 #=> 2//3 (Rational{Int64})
|
||||
3 # => 3 (Int64)
|
||||
3.2 # => 3.2 (Float64)
|
||||
2 + 1im # => 2 + 1im (Complex{Int64})
|
||||
2//3 # => 2//3 (Rational{Int64})
|
||||
|
||||
# All of the normal infix operators are available.
|
||||
1 + 1 #=> 2
|
||||
8 - 1 #=> 7
|
||||
10 * 2 #=> 20
|
||||
35 / 5 #=> 7.0
|
||||
5 / 2 #=> 2.5 # dividing an Int by an Int always results in a Float
|
||||
div(5, 2) #=> 2 # for a truncated result, use div
|
||||
5 \ 35 #=> 7.0
|
||||
2 ^ 2 #=> 4 # power, not bitwise xor
|
||||
12 % 10 #=> 2
|
||||
1 + 1 # => 2
|
||||
8 - 1 # => 7
|
||||
10 * 2 # => 20
|
||||
35 / 5 # => 7.0
|
||||
5 / 2 # => 2.5 # dividing an Int by an Int always results in a Float
|
||||
div(5, 2) # => 2 # for a truncated result, use div
|
||||
5 \ 35 # => 7.0
|
||||
2 ^ 2 # => 4 # power, not bitwise xor
|
||||
12 % 10 # => 2
|
||||
|
||||
# Enforce precedence with parentheses
|
||||
(1 + 3) * 2 #=> 8
|
||||
(1 + 3) * 2 # => 8
|
||||
|
||||
# Bitwise Operators
|
||||
~2 #=> -3 # bitwise not
|
||||
3 & 5 #=> 1 # bitwise and
|
||||
2 | 4 #=> 6 # bitwise or
|
||||
2 $ 4 #=> 6 # bitwise xor
|
||||
2 >>> 1 #=> 1 # logical shift right
|
||||
2 >> 1 #=> 1 # arithmetic shift right
|
||||
2 << 1 #=> 4 # logical/arithmetic shift left
|
||||
~2 # => -3 # bitwise not
|
||||
3 & 5 # => 1 # bitwise and
|
||||
2 | 4 # => 6 # bitwise or
|
||||
2 $ 4 # => 6 # bitwise xor
|
||||
2 >>> 1 # => 1 # logical shift right
|
||||
2 >> 1 # => 1 # arithmetic shift right
|
||||
2 << 1 # => 4 # logical/arithmetic shift left
|
||||
|
||||
# You can use the bits function to see the binary representation of a number.
|
||||
bits(12345)
|
||||
#=> "0000000000000000000000000000000000000000000000000011000000111001"
|
||||
# => "0000000000000000000000000000000000000000000000000011000000111001"
|
||||
bits(12345.0)
|
||||
#=> "0100000011001000000111001000000000000000000000000000000000000000"
|
||||
# => "0100000011001000000111001000000000000000000000000000000000000000"
|
||||
|
||||
# Boolean values are primitives
|
||||
true
|
||||
false
|
||||
|
||||
# Boolean operators
|
||||
!true #=> false
|
||||
!false #=> true
|
||||
1 == 1 #=> true
|
||||
2 == 1 #=> false
|
||||
1 != 1 #=> false
|
||||
2 != 1 #=> true
|
||||
1 < 10 #=> true
|
||||
1 > 10 #=> false
|
||||
2 <= 2 #=> true
|
||||
2 >= 2 #=> true
|
||||
!true # => false
|
||||
!false # => true
|
||||
1 == 1 # => true
|
||||
2 == 1 # => false
|
||||
1 != 1 # => false
|
||||
2 != 1 # => true
|
||||
1 < 10 # => true
|
||||
1 > 10 # => false
|
||||
2 <= 2 # => true
|
||||
2 >= 2 # => true
|
||||
# Comparisons can be chained
|
||||
1 < 2 < 3 #=> true
|
||||
2 < 3 < 2 #=> false
|
||||
1 < 2 < 3 # => true
|
||||
2 < 3 < 2 # => false
|
||||
|
||||
# Strings are created with "
|
||||
"This is a string."
|
||||
@ -81,12 +81,12 @@ false
|
||||
'a'
|
||||
|
||||
# A string can be indexed like an array of characters
|
||||
"This is a string"[1] #=> 'T' # Julia indexes from 1
|
||||
"This is a string"[1] # => 'T' # Julia indexes from 1
|
||||
# However, this is will not work well for UTF8 strings,
|
||||
# so iterating over strings is recommended (map, for loops, etc).
|
||||
|
||||
# $ can be used for string interpolation:
|
||||
"2 + 2 = $(2 + 2)" #=> "2 + 2 = 4"
|
||||
"2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
|
||||
# You can put any Julia expression inside the parenthesis.
|
||||
|
||||
# Another way to format strings is the printf macro.
|
||||
@ -100,24 +100,24 @@ println("I'm Julia. Nice to meet you!")
|
||||
####################################################
|
||||
|
||||
# You don't declare variables before assigning to them.
|
||||
some_var = 5 #=> 5
|
||||
some_var #=> 5
|
||||
some_var = 5 # => 5
|
||||
some_var # => 5
|
||||
|
||||
# Accessing a previously unassigned variable is an error
|
||||
try
|
||||
some_other_var #=> ERROR: some_other_var not defined
|
||||
some_other_var # => ERROR: some_other_var not defined
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
|
||||
# Variable names start with a letter.
|
||||
# After that, you can use letters, digits, underscores, and exclamation points.
|
||||
SomeOtherVar123! = 6 #=> 6
|
||||
SomeOtherVar123! = 6 # => 6
|
||||
|
||||
# You can also use unicode characters
|
||||
☃ = 8 #=> 8
|
||||
☃ = 8 # => 8
|
||||
# These are especially handy for mathematical notation
|
||||
2 * π #=> 6.283185307179586
|
||||
2 * π # => 6.283185307179586
|
||||
|
||||
# A note on naming conventions in Julia:
|
||||
#
|
||||
@ -133,49 +133,49 @@ SomeOtherVar123! = 6 #=> 6
|
||||
# functions are sometimes called mutating functions or in-place functions.
|
||||
|
||||
# Arrays store a sequence of values indexed by integers 1 through n:
|
||||
a = Int64[] #=> 0-element Int64 Array
|
||||
a = Int64[] # => 0-element Int64 Array
|
||||
|
||||
# 1-dimensional array literals can be written with comma-separated values.
|
||||
b = [4, 5, 6] #=> 3-element Int64 Array: [4, 5, 6]
|
||||
b[1] #=> 4
|
||||
b[end] #=> 6
|
||||
b = [4, 5, 6] # => 3-element Int64 Array: [4, 5, 6]
|
||||
b[1] # => 4
|
||||
b[end] # => 6
|
||||
|
||||
# 2-dimentional arrays use space-separated values and semicolon-separated rows.
|
||||
matrix = [1 2; 3 4] #=> 2x2 Int64 Array: [1 2; 3 4]
|
||||
matrix = [1 2; 3 4] # => 2x2 Int64 Array: [1 2; 3 4]
|
||||
|
||||
# Add stuff to the end of a list with push! and append!
|
||||
push!(a,1) #=> [1]
|
||||
push!(a,2) #=> [1,2]
|
||||
push!(a,4) #=> [1,2,4]
|
||||
push!(a,3) #=> [1,2,4,3]
|
||||
append!(a,b) #=> [1,2,4,3,4,5,6]
|
||||
push!(a,1) # => [1]
|
||||
push!(a,2) # => [1,2]
|
||||
push!(a,4) # => [1,2,4]
|
||||
push!(a,3) # => [1,2,4,3]
|
||||
append!(a,b) # => [1,2,4,3,4,5,6]
|
||||
|
||||
# Remove from the end with pop
|
||||
pop!(b) #=> 6 and b is now [4,5]
|
||||
pop!(b) # => 6 and b is now [4,5]
|
||||
|
||||
# Let's put it back
|
||||
push!(b,6) # b is now [4,5,6] again.
|
||||
|
||||
a[1] #=> 1 # remember that Julia indexes from 1, not 0!
|
||||
a[1] # => 1 # remember that Julia indexes from 1, not 0!
|
||||
|
||||
# end is a shorthand for the last index. It can be used in any
|
||||
# indexing expression
|
||||
a[end] #=> 6
|
||||
a[end] # => 6
|
||||
|
||||
# we also have shift and unshift
|
||||
shift!(a) #=> 1 and a is now [2,4,3,4,5,6]
|
||||
unshift!(a,7) #=> [7,2,4,3,4,5,6]
|
||||
shift!(a) # => 1 and a is now [2,4,3,4,5,6]
|
||||
unshift!(a,7) # => [7,2,4,3,4,5,6]
|
||||
|
||||
# Function names that end in exclamations points indicate that they modify
|
||||
# their argument.
|
||||
arr = [5,4,6] #=> 3-element Int64 Array: [5,4,6]
|
||||
sort(arr) #=> [4,5,6]; arr is still [5,4,6]
|
||||
sort!(arr) #=> [4,5,6]; arr is now [4,5,6]
|
||||
arr = [5,4,6] # => 3-element Int64 Array: [5,4,6]
|
||||
sort(arr) # => [4,5,6]; arr is still [5,4,6]
|
||||
sort!(arr) # => [4,5,6]; arr is now [4,5,6]
|
||||
|
||||
# Looking out of bounds is a BoundsError
|
||||
try
|
||||
a[0] #=> ERROR: BoundsError() in getindex at array.jl:270
|
||||
a[end+1] #=> ERROR: BoundsError() in getindex at array.jl:270
|
||||
a[0] # => ERROR: BoundsError() in getindex at array.jl:270
|
||||
a[end+1] # => ERROR: BoundsError() in getindex at array.jl:270
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
@ -185,110 +185,110 @@ end
|
||||
# inside the julia folder to find these files.
|
||||
|
||||
# You can initialize arrays from ranges
|
||||
a = [1:5] #=> 5-element Int64 Array: [1,2,3,4,5]
|
||||
a = [1:5] # => 5-element Int64 Array: [1,2,3,4,5]
|
||||
|
||||
# You can look at ranges with slice syntax.
|
||||
a[1:3] #=> [1, 2, 3]
|
||||
a[2:] #=> [2, 3, 4, 5]
|
||||
a[2:end] #=> [2, 3, 4, 5]
|
||||
a[1:3] # => [1, 2, 3]
|
||||
a[2:] # => [2, 3, 4, 5]
|
||||
a[2:end] # => [2, 3, 4, 5]
|
||||
|
||||
# Remove elements from an array by index with splice!
|
||||
arr = [3,4,5]
|
||||
splice!(arr,2) #=> 4 ; arr is now [3,5]
|
||||
splice!(arr,2) # => 4 ; arr is now [3,5]
|
||||
|
||||
# Concatenate lists with append!
|
||||
b = [1,2,3]
|
||||
append!(a,b) # Now a is [1, 2, 3, 4, 5, 1, 2, 3]
|
||||
|
||||
# Check for existence in a list with in
|
||||
in(1, a) #=> true
|
||||
in(1, a) # => true
|
||||
|
||||
# Examine the length with length
|
||||
length(a) #=> 8
|
||||
length(a) # => 8
|
||||
|
||||
# Tuples are immutable.
|
||||
tup = (1, 2, 3) #=> (1,2,3) # an (Int64,Int64,Int64) tuple.
|
||||
tup[1] #=> 1
|
||||
tup = (1, 2, 3) # => (1,2,3) # an (Int64,Int64,Int64) tuple.
|
||||
tup[1] # => 1
|
||||
try:
|
||||
tup[1] = 3 #=> ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64)
|
||||
tup[1] = 3 # => ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64)
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
|
||||
# Many list functions also work on tuples
|
||||
length(tup) #=> 3
|
||||
tup[1:2] #=> (1,2)
|
||||
in(2, tup) #=> true
|
||||
length(tup) # => 3
|
||||
tup[1:2] # => (1,2)
|
||||
in(2, tup) # => true
|
||||
|
||||
# You can unpack tuples into variables
|
||||
a, b, c = (1, 2, 3) #=> (1,2,3) # a is now 1, b is now 2 and c is now 3
|
||||
a, b, c = (1, 2, 3) # => (1,2,3) # a is now 1, b is now 2 and c is now 3
|
||||
|
||||
# Tuples are created even if you leave out the parentheses
|
||||
d, e, f = 4, 5, 6 #=> (4,5,6)
|
||||
d, e, f = 4, 5, 6 # => (4,5,6)
|
||||
|
||||
# A 1-element tuple is distinct from the value it contains
|
||||
(1,) == 1 #=> false
|
||||
(1) == 1 #=> true
|
||||
(1,) == 1 # => false
|
||||
(1) == 1 # => true
|
||||
|
||||
# Look how easy it is to swap two values
|
||||
e, d = d, e #=> (5,4) # d is now 5 and e is now 4
|
||||
e, d = d, e # => (5,4) # d is now 5 and e is now 4
|
||||
|
||||
|
||||
# Dictionaries store mappings
|
||||
empty_dict = Dict() #=> Dict{Any,Any}()
|
||||
empty_dict = Dict() # => Dict{Any,Any}()
|
||||
|
||||
# You can create a dictionary using a literal
|
||||
filled_dict = ["one"=> 1, "two"=> 2, "three"=> 3]
|
||||
# => Dict{ASCIIString,Int64}
|
||||
|
||||
# Look up values with []
|
||||
filled_dict["one"] #=> 1
|
||||
filled_dict["one"] # => 1
|
||||
|
||||
# Get all keys
|
||||
keys(filled_dict)
|
||||
#=> KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
|
||||
# => KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
|
||||
# Note - dictionary keys are not sorted or in the order you inserted them.
|
||||
|
||||
# Get all values
|
||||
values(filled_dict)
|
||||
#=> ValueIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
|
||||
# => ValueIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2])
|
||||
# Note - Same as above regarding key ordering.
|
||||
|
||||
# Check for existence of keys in a dictionary with in, haskey
|
||||
in(("one", 1), filled_dict) #=> true
|
||||
in(("two", 3), filled_dict) #=> false
|
||||
haskey(filled_dict, "one") #=> true
|
||||
haskey(filled_dict, 1) #=> false
|
||||
in(("one", 1), filled_dict) # => true
|
||||
in(("two", 3), filled_dict) # => false
|
||||
haskey(filled_dict, "one") # => true
|
||||
haskey(filled_dict, 1) # => false
|
||||
|
||||
# Trying to look up a non-existant key will raise an error
|
||||
try
|
||||
filled_dict["four"] #=> ERROR: key not found: four in getindex at dict.jl:489
|
||||
filled_dict["four"] # => ERROR: key not found: four in getindex at dict.jl:489
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
|
||||
# Use the get method to avoid that error by providing a default value
|
||||
# get(dictionary,key,default_value)
|
||||
get(filled_dict,"one",4) #=> 1
|
||||
get(filled_dict,"four",4) #=> 4
|
||||
get(filled_dict,"one",4) # => 1
|
||||
get(filled_dict,"four",4) # => 4
|
||||
|
||||
# Use Sets to represent collections of unordered, unique values
|
||||
empty_set = Set() #=> Set{Any}()
|
||||
empty_set = Set() # => Set{Any}()
|
||||
# Initialize a set with values
|
||||
filled_set = Set(1,2,2,3,4) #=> Set{Int64}(1,2,3,4)
|
||||
filled_set = Set(1,2,2,3,4) # => Set{Int64}(1,2,3,4)
|
||||
|
||||
# Add more values to a set
|
||||
push!(filled_set,5) #=> Set{Int64}(5,4,2,3,1)
|
||||
push!(filled_set,5) # => Set{Int64}(5,4,2,3,1)
|
||||
|
||||
# Check if the values are in the set
|
||||
in(2, filled_set) #=> true
|
||||
in(10, filled_set) #=> false
|
||||
in(2, filled_set) # => true
|
||||
in(10, filled_set) # => false
|
||||
|
||||
# There are functions for set intersection, union, and difference.
|
||||
other_set = Set(3, 4, 5, 6) #=> Set{Int64}(6,4,5,3)
|
||||
intersect(filled_set, other_set) #=> Set{Int64}(3,4,5)
|
||||
union(filled_set, other_set) #=> Set{Int64}(1,2,3,4,5,6)
|
||||
setdiff(Set(1,2,3,4),Set(2,3,5)) #=> Set{Int64}(1,4)
|
||||
other_set = Set(3, 4, 5, 6) # => Set{Int64}(6,4,5,3)
|
||||
intersect(filled_set, other_set) # => Set{Int64}(3,4,5)
|
||||
union(filled_set, other_set) # => Set{Int64}(1,2,3,4,5,6)
|
||||
setdiff(Set(1,2,3,4),Set(2,3,5)) # => Set{Int64}(1,4)
|
||||
|
||||
|
||||
####################################################
|
||||
@ -306,7 +306,7 @@ elseif some_var < 10 # This elseif clause is optional.
|
||||
else # The else clause is optional too.
|
||||
println("some_var is indeed 10.")
|
||||
end
|
||||
#=> prints "some var is smaller than 10"
|
||||
# => prints "some var is smaller than 10"
|
||||
|
||||
|
||||
# For loops iterate over iterables.
|
||||
@ -363,7 +363,7 @@ try
|
||||
catch e
|
||||
println("caught it $e")
|
||||
end
|
||||
#=> caught it ErrorException("help")
|
||||
# => caught it ErrorException("help")
|
||||
|
||||
|
||||
####################################################
|
||||
@ -381,7 +381,7 @@ function add(x, y)
|
||||
x + y
|
||||
end
|
||||
|
||||
add(5, 6) #=> 11 after printing out "x is 5 and y is 6"
|
||||
add(5, 6) # => 11 after printing out "x is 5 and y is 6"
|
||||
|
||||
# You can define functions that take a variable number of
|
||||
# positional arguments
|
||||
@ -389,20 +389,20 @@ function varargs(args...)
|
||||
return args
|
||||
# use the keyword return to return anywhere in the function
|
||||
end
|
||||
#=> varargs (generic function with 1 method)
|
||||
# => varargs (generic function with 1 method)
|
||||
|
||||
varargs(1,2,3) #=> (1,2,3)
|
||||
varargs(1,2,3) # => (1,2,3)
|
||||
|
||||
# The ... is called a splat.
|
||||
# We just used it in a function definition.
|
||||
# It can also be used in a fuction call,
|
||||
# where it will splat an Array or Tuple's contents into the argument list.
|
||||
Set([1,2,3]) #=> Set{Array{Int64,1}}([1,2,3]) # produces a Set of Arrays
|
||||
Set([1,2,3]...) #=> Set{Int64}(1,2,3) # this is equivalent to Set(1,2,3)
|
||||
Set([1,2,3]) # => Set{Array{Int64,1}}([1,2,3]) # produces a Set of Arrays
|
||||
Set([1,2,3]...) # => Set{Int64}(1,2,3) # this is equivalent to Set(1,2,3)
|
||||
|
||||
x = (1,2,3) #=> (1,2,3)
|
||||
Set(x) #=> Set{(Int64,Int64,Int64)}((1,2,3)) # a Set of Tuples
|
||||
Set(x...) #=> Set{Int64}(2,3,1)
|
||||
x = (1,2,3) # => (1,2,3)
|
||||
Set(x) # => Set{(Int64,Int64,Int64)}((1,2,3)) # a Set of Tuples
|
||||
Set(x...) # => Set{Int64}(2,3,1)
|
||||
|
||||
|
||||
# You can define functions with optional positional arguments
|
||||
@ -410,12 +410,12 @@ function defaults(a,b,x=5,y=6)
|
||||
return "$a $b and $x $y"
|
||||
end
|
||||
|
||||
defaults('h','g') #=> "h g and 5 6"
|
||||
defaults('h','g','j') #=> "h g and j 6"
|
||||
defaults('h','g','j','k') #=> "h g and j k"
|
||||
defaults('h','g') # => "h g and 5 6"
|
||||
defaults('h','g','j') # => "h g and j 6"
|
||||
defaults('h','g','j','k') # => "h g and j k"
|
||||
try
|
||||
defaults('h') #=> ERROR: no method defaults(Char,)
|
||||
defaults() #=> ERROR: no methods defaults()
|
||||
defaults('h') # => ERROR: no method defaults(Char,)
|
||||
defaults() # => ERROR: no methods defaults()
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
@ -425,9 +425,9 @@ function keyword_args(;k1=4,name2="hello") # note the ;
|
||||
return ["k1"=>k1,"name2"=>name2]
|
||||
end
|
||||
|
||||
keyword_args(name2="ness") #=> ["name2"=>"ness","k1"=>4]
|
||||
keyword_args(k1="mine") #=> ["k1"=>"mine","name2"=>"hello"]
|
||||
keyword_args() #=> ["name2"=>"hello","k1"=>4]
|
||||
keyword_args(name2="ness") # => ["name2"=>"ness","k1"=>4]
|
||||
keyword_args(k1="mine") # => ["k1"=>"mine","name2"=>"hello"]
|
||||
keyword_args() # => ["name2"=>"hello","k1"=>4]
|
||||
|
||||
# You can combine all kinds of arguments in the same function
|
||||
function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo")
|
||||
@ -451,7 +451,7 @@ function create_adder(x)
|
||||
end
|
||||
|
||||
# This is "stabby lambda syntax" for creating anonymous functions
|
||||
(x -> x > 2)(3) #=> true
|
||||
(x -> x > 2)(3) # => true
|
||||
|
||||
# This function is identical to create_adder implementation above.
|
||||
function create_adder(x)
|
||||
@ -467,16 +467,16 @@ function create_adder(x)
|
||||
end
|
||||
|
||||
add_10 = create_adder(10)
|
||||
add_10(3) #=> 13
|
||||
add_10(3) # => 13
|
||||
|
||||
|
||||
# There are built-in higher order functions
|
||||
map(add_10, [1,2,3]) #=> [11, 12, 13]
|
||||
filter(x -> x > 5, [3, 4, 5, 6, 7]) #=> [6, 7]
|
||||
map(add_10, [1,2,3]) # => [11, 12, 13]
|
||||
filter(x -> x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
|
||||
|
||||
# We can use list comprehensions for nicer maps
|
||||
[add_10(i) for i=[1, 2, 3]] #=> [11, 12, 13]
|
||||
[add_10(i) for i in [1, 2, 3]] #=> [11, 12, 13]
|
||||
[add_10(i) for i=[1, 2, 3]] # => [11, 12, 13]
|
||||
[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
|
||||
|
||||
####################################################
|
||||
## 5. Types
|
||||
@ -485,11 +485,11 @@ filter(x -> x > 5, [3, 4, 5, 6, 7]) #=> [6, 7]
|
||||
# Julia has a type system.
|
||||
# Every value has a type; variables do not have types themselves.
|
||||
# You can use the `typeof` function to get the type of a value.
|
||||
typeof(5) #=> Int64
|
||||
typeof(5) # => Int64
|
||||
|
||||
# Types are first-class values
|
||||
typeof(Int64) #=> DataType
|
||||
typeof(DataType) #=> DataType
|
||||
typeof(Int64) # => DataType
|
||||
typeof(DataType) # => DataType
|
||||
# DataType is the type that represents types, including itself.
|
||||
|
||||
# Types are used for documentation, optimizations, and dispatch.
|
||||
@ -510,10 +510,10 @@ end
|
||||
|
||||
# The default constructor's arguments are the properties
|
||||
# of the type, in the order they are listed in the definition
|
||||
tigger = Tiger(3.5,"orange") #=> Tiger(3.5,"orange")
|
||||
tigger = Tiger(3.5,"orange") # => Tiger(3.5,"orange")
|
||||
|
||||
# The type doubles as the constructor function for values of that type
|
||||
sherekhan = typeof(tigger)(5.6,"fire") #=> Tiger(5.6,"fire")
|
||||
sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire")
|
||||
|
||||
# These struct-style types are called concrete types
|
||||
# They can be instantiated, but cannot have subtypes.
|
||||
@ -524,23 +524,23 @@ abstract Cat # just a name and point in the type hierarchy
|
||||
|
||||
# Abstract types cannot be instantiated, but can have subtypes.
|
||||
# For example, Number is an abstract type
|
||||
subtypes(Number) #=> 6-element Array{Any,1}:
|
||||
subtypes(Number) # => 6-element Array{Any,1}:
|
||||
# Complex{Float16}
|
||||
# Complex{Float32}
|
||||
# Complex{Float64}
|
||||
# Complex{T<:Real}
|
||||
# ImaginaryUnit
|
||||
# Real
|
||||
subtypes(Cat) #=> 0-element Array{Any,1}
|
||||
subtypes(Cat) # => 0-element Array{Any,1}
|
||||
|
||||
# Every type has a super type; use the `super` function to get it.
|
||||
typeof(5) #=> Int64
|
||||
super(Int64) #=> Signed
|
||||
super(Signed) #=> Real
|
||||
super(Real) #=> Number
|
||||
super(Number) #=> Any
|
||||
super(super(Signed)) #=> Number
|
||||
super(Any) #=> Any
|
||||
typeof(5) # => Int64
|
||||
super(Int64) # => Signed
|
||||
super(Signed) # => Real
|
||||
super(Real) # => Number
|
||||
super(Number) # => Any
|
||||
super(super(Signed)) # => Number
|
||||
super(Any) # => Any
|
||||
# All of these type, except for Int64, are abstract.
|
||||
|
||||
# <: is the subtyping operator
|
||||
@ -588,23 +588,23 @@ function meow(animal::Tiger)
|
||||
end
|
||||
|
||||
# Testing the meow function
|
||||
meow(tigger) #=> "rawwr"
|
||||
meow(Lion("brown","ROAAR")) #=> "ROAAR"
|
||||
meow(Panther()) #=> "grrr"
|
||||
meow(tigger) # => "rawwr"
|
||||
meow(Lion("brown","ROAAR")) # => "ROAAR"
|
||||
meow(Panther()) # => "grrr"
|
||||
|
||||
# Review the local type hierarchy
|
||||
issubtype(Tiger,Cat) #=> false
|
||||
issubtype(Lion,Cat) #=> true
|
||||
issubtype(Panther,Cat) #=> true
|
||||
issubtype(Tiger,Cat) # => false
|
||||
issubtype(Lion,Cat) # => true
|
||||
issubtype(Panther,Cat) # => true
|
||||
|
||||
# Defining a function that takes Cats
|
||||
function pet_cat(cat::Cat)
|
||||
println("The cat says $(meow(cat))")
|
||||
end
|
||||
|
||||
pet_cat(Lion("42")) #=> prints "The cat says 42"
|
||||
pet_cat(Lion("42")) # => prints "The cat says 42"
|
||||
try
|
||||
pet_cat(tigger) #=> ERROR: no method pet_cat(Tiger,)
|
||||
pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,)
|
||||
catch e
|
||||
println(e)
|
||||
end
|
||||
@ -617,31 +617,31 @@ end
|
||||
function fight(t::Tiger,c::Cat)
|
||||
println("The $(t.coatcolor) tiger wins!")
|
||||
end
|
||||
#=> fight (generic function with 1 method)
|
||||
# => fight (generic function with 1 method)
|
||||
|
||||
fight(tigger,Panther()) #=> prints The orange tiger wins!
|
||||
fight(tigger,Lion("ROAR")) #=> prints The orange tiger wins!
|
||||
fight(tigger,Panther()) # => prints The orange tiger wins!
|
||||
fight(tigger,Lion("ROAR")) # => prints The orange tiger wins!
|
||||
|
||||
# Let's change the behavior when the Cat is specifically a Lion
|
||||
fight(t::Tiger,l::Lion) = println("The $(l.mane_color)-maned lion wins!")
|
||||
#=> fight (generic function with 2 methods)
|
||||
# => fight (generic function with 2 methods)
|
||||
|
||||
fight(tigger,Panther()) #=> prints The orange tiger wins!
|
||||
fight(tigger,Lion("ROAR")) #=> prints The green-maned lion wins!
|
||||
fight(tigger,Panther()) # => prints The orange tiger wins!
|
||||
fight(tigger,Lion("ROAR")) # => prints The green-maned lion wins!
|
||||
|
||||
# We don't need a Tiger in order to fight
|
||||
fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))")
|
||||
#=> fight (generic function with 3 methods)
|
||||
# => fight (generic function with 3 methods)
|
||||
|
||||
fight(Lion("balooga!"),Panther()) #=> prints The victorious cat says grrr
|
||||
fight(Lion("balooga!"),Panther()) # => prints The victorious cat says grrr
|
||||
try
|
||||
fight(Panther(),Lion("RAWR")) #=> ERROR: no method fight(Panther,Lion)
|
||||
fight(Panther(),Lion("RAWR")) # => ERROR: no method fight(Panther,Lion)
|
||||
catch
|
||||
end
|
||||
|
||||
# Also let the cat go first
|
||||
fight(c::Cat,l::Lion) = println("The cat beats the Lion")
|
||||
#=> Warning: New definition
|
||||
# => Warning: New definition
|
||||
# fight(Cat,Lion) at none:1
|
||||
# is ambiguous with
|
||||
# fight(Lion,Cat) at none:2.
|
||||
@ -651,11 +651,11 @@ fight(c::Cat,l::Lion) = println("The cat beats the Lion")
|
||||
#fight (generic function with 4 methods)
|
||||
|
||||
# This warning is because it's unclear which fight will be called in:
|
||||
fight(Lion("RAR"),Lion("brown","rarrr")) #=> prints The victorious cat says rarrr
|
||||
fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr
|
||||
# The result may be different in other versions of Julia
|
||||
|
||||
fight(l::Lion,l2::Lion) = println("The lions come to a tie")
|
||||
fight(Lion("RAR"),Lion("brown","rarrr")) #=> prints The lions come to a tie
|
||||
fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The lions come to a tie
|
||||
|
||||
|
||||
# Under the hood
|
||||
|
||||
Loading…
Reference in New Issue
Block a user