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mostly just spaces between arguments
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@ -31,7 +31,7 @@ This is based on Julia 1.0.0
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3 # => 3 (Int64)
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3.2 # => 3.2 (Float64)
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2 + 1im # => 2 + 1im (Complex{Int64})
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2//3 # => 2//3 (Rational{Int64})
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2 // 3 # => 2//3 (Rational{Int64})
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# All of the normal infix operators are available.
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1 + 1 # => 2
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@ -41,7 +41,7 @@ This is based on Julia 1.0.0
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5 / 2 # => 2.5 # dividing an Int by an Int always results in a Float
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div(5, 2) # => 2 # for a truncated result, use div
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5 \ 35 # => 7.0
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2 ^ 2 # => 4 # power, not bitwise xor
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2^2 # => 4 # power, not bitwise xor
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12 % 10 # => 2
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# Enforce precedence with parentheses
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@ -83,7 +83,7 @@ false
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# Strings are created with "
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try
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"This is a string."
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"This is a string."
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catch ; end
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# Julia has several types of strings, including ASCIIString and UTF8String.
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@ -91,19 +91,19 @@ catch ; end
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# Character literals are written with '
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try
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'a'
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'a'
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catch ; end
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# Some strings can be indexed like an array of characters
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try
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"This is a string"[1] # => 'T' # Julia indexes from 1
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"This is a string"[1] # => 'T' # Julia indexes from 1
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catch ; end
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# However, this is will not work well for UTF8 strings,
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# so iterating over strings is recommended (map, for loops, etc).
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# $ can be used for string interpolation:
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try
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"2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
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"2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
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catch ; end
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# You can put any Julia expression inside the parentheses.
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@ -116,7 +116,7 @@ println("I'm Julia. Nice to meet you!")
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# String can be compared lexicographically
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"good" > "bye" # => true
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"good" == "good" # => true
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"1 + 2 = 3" == "1 + 2 = $(1+2)" # => true
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"1 + 2 = 3" == "1 + 2 = $(1 + 2)" # => true
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####################################################
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## 2. Variables and Collections
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@ -172,17 +172,17 @@ matrix = [1 2; 3 4] # => 2x2 Int64 Array: [1 2; 3 4]
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b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6]
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# Add stuff to the end of a list with push! and append!
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push!(a,1) # => [1]
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push!(a,2) # => [1,2]
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push!(a,4) # => [1,2,4]
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push!(a,3) # => [1,2,4,3]
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append!(a,b) # => [1,2,4,3,4,5,6]
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push!(a, 1) # => [1]
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push!(a, 2) # => [1,2]
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push!(a, 4) # => [1,2,4]
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push!(a, 3) # => [1,2,4,3]
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append!(a, b) # => [1,2,4,3,4,5,6]
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# Remove from the end with pop
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pop!(b) # => 6 and b is now [4,5]
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# Let's put it back
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push!(b,6) # b is now [4,5,6] again.
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push!(b, 6) # b is now [4,5,6] again.
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a[1] # => 1 # remember that Julia indexes from 1, not 0!
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@ -192,7 +192,7 @@ a[end] # => 6
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# we also have shift and unshift
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shift!(a) # => 1 and a is now [2,4,3,4,5,6]
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unshift!(a,7) # => [7,2,4,3,4,5,6]
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unshift!(a, 7) # => [7,2,4,3,4,5,6]
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# Function names that end in exclamations points indicate that they modify
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# their argument.
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@ -203,7 +203,7 @@ sort!(arr) # => [4,5,6]; arr is now [4,5,6]
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# Looking out of bounds is a BoundsError
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try
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a[0] # => ERROR: BoundsError() in getindex at array.jl:270
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a[end+1] # => ERROR: BoundsError() in getindex at array.jl:270
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a[end + 1] # => ERROR: BoundsError() in getindex at array.jl:270
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catch e
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println(e)
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end
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@ -221,11 +221,11 @@ a[2:end] # => [2, 3, 4, 5]
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# Remove elements from an array by index with splice!
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arr = [3,4,5]
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splice!(arr,2) # => 4 ; arr is now [3,5]
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splice!(arr, 2) # => 4 ; arr is now [3,5]
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# Concatenate lists with append!
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b = [1,2,3]
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append!(a,b) # Now a is [1, 2, 3, 4, 5, 1, 2, 3]
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append!(a, b) # Now a is [1, 2, 3, 4, 5, 1, 2, 3]
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# Check for existence in a list with in
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in(1, a) # => true
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@ -236,7 +236,7 @@ length(a) # => 8
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# Tuples are immutable.
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tup = (1, 2, 3) # => (1,2,3) # an (Int64,Int64,Int64) tuple.
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tup[1] # => 1
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try:
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try:
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tup[1] = 3 # => ERROR: no method setindex!((Int64,Int64,Int64),Int64,Int64)
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catch e
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println(e)
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@ -265,7 +265,7 @@ e, d = d, e # => (5,4) # d is now 5 and e is now 4
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empty_dict = Dict() # => Dict{Any,Any}()
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# You can create a dictionary using a literal
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filled_dict = Dict("one"=> 1, "two"=> 2, "three"=> 3)
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filled_dict = Dict("one" => 1, "two" => 2, "three" => 3)
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# => Dict{ASCIIString,Int64}
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# Look up values with []
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@ -296,8 +296,8 @@ end
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# Use the get method to avoid that error by providing a default value
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# get(dictionary,key,default_value)
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get(filled_dict,"one",4) # => 1
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get(filled_dict,"four",4) # => 4
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get(filled_dict, "one", 4) # => 1
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get(filled_dict, "four", 4) # => 4
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# Use Sets to represent collections of unordered, unique values
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empty_set = Set() # => Set{Any}()
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@ -305,7 +305,7 @@ empty_set = Set() # => Set{Any}()
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filled_set = Set([1,2,2,3,4]) # => Set{Int64}(1,2,3,4)
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# Add more values to a set
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push!(filled_set,5) # => Set{Int64}(5,4,2,3,1)
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push!(filled_set, 5) # => Set{Int64}(5,4,2,3,1)
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# Check if the values are in the set
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in(2, filled_set) # => true
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@ -315,7 +315,7 @@ in(10, filled_set) # => false
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other_set = Set([3, 4, 5, 6]) # => Set{Int64}(6,4,5,3)
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intersect(filled_set, other_set) # => Set{Int64}(3,4,5)
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union(filled_set, other_set) # => Set{Int64}(1,2,3,4,5,6)
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setdiff(Set([1,2,3,4]),Set([2,3,5])) # => Set{Int64}(1,4)
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setdiff(Set([1,2,3,4]), Set([2,3,5])) # => Set{Int64}(1,4)
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####################################################
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@ -338,7 +338,7 @@ end
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# For loops iterate over iterables.
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# Iterable types include Range, Array, Set, Dict, and AbstractString.
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for animal=["dog", "cat", "mouse"]
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for animal = ["dog", "cat", "mouse"]
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println("$animal is a mammal")
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# You can use $ to interpolate variables or expression into strings
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end
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@ -356,7 +356,7 @@ end
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# cat is a mammal
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# mouse is a mammal
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for a in Dict("dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal")
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for a in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
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println("$(a[1]) is a $(a[2])")
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end
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# prints:
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@ -364,7 +364,7 @@ end
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# cat is a mammal
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# mouse is a mammal
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for (k,v) in Dict("dog"=>"mammal","cat"=>"mammal","mouse"=>"mammal")
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for (k, v) in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
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println("$k is a $v")
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end
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# prints:
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@ -386,9 +386,9 @@ end
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# Handle exceptions with a try/catch block
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try
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error("help")
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error("help")
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catch e
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println("caught it $e")
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println("caught it $e")
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end
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# => caught it ErrorException("help")
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@ -426,7 +426,7 @@ function varargs(args...)
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end
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# => varargs (generic function with 1 method)
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varargs(1,2,3) # => (1,2,3)
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varargs(1, 2, 3) # => (1,2,3)
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# The ... is called a splat.
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# We just used it in a function definition.
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@ -434,18 +434,18 @@ varargs(1,2,3) # => (1,2,3)
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# where it will splat an Array or Tuple's contents into the argument list.
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add([5,6]...) # this is equivalent to add(5,6)
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x = (5,6) # => (5,6)
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x = (5, 6) # => (5,6)
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add(x...) # this is equivalent to add(5,6)
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# You can define functions with optional positional arguments
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function defaults(a,b,x=5,y=6)
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function defaults(a, b, x=5, y=6)
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return "$a $b and $x $y"
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end
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defaults('h','g') # => "h g and 5 6"
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defaults('h','g','j') # => "h g and j 6"
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defaults('h','g','j','k') # => "h g and j k"
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defaults('h', 'g') # => "h g and 5 6"
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defaults('h', 'g', 'j') # => "h g and j 6"
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defaults('h', 'g', 'j', 'k') # => "h g and j k"
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try
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defaults('h') # => ERROR: no method defaults(Char,)
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defaults() # => ERROR: no methods defaults()
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@ -454,8 +454,8 @@ catch e
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end
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# You can define functions that take keyword arguments
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function keyword_args(;k1=4,name2="hello") # note the ;
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return Dict("k1"=>k1,"name2"=>name2)
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function keyword_args(;k1=4, name2="hello") # note the ;
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return Dict("k1" => k1, "name2" => name2)
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end
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keyword_args(name2="ness") # => ["name2"=>"ness","k1"=>4]
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@ -508,7 +508,7 @@ map(add_10, [1,2,3]) # => [11, 12, 13]
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filter(x -> x > 5, [3, 4, 5, 6, 7]) # => [6, 7]
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# We can use list comprehensions for nicer maps
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[add_10(i) for i=[1, 2, 3]] # => [11, 12, 13]
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[add_10(i) for i = [1, 2, 3]] # => [11, 12, 13]
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[add_10(i) for i in [1, 2, 3]] # => [11, 12, 13]
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####################################################
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@ -537,16 +537,16 @@ typeof(DataType) # => DataType
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# ...
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# end
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type Tiger
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taillength::Float64
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coatcolor # not including a type annotation is the same as `::Any`
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taillength::Float64
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coatcolor # not including a type annotation is the same as `::Any`
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end
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# The default constructor's arguments are the properties
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# of the type, in the order they are listed in the definition
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tigger = Tiger(3.5,"orange") # => Tiger(3.5,"orange")
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tigger = Tiger(3.5, "orange") # => Tiger(3.5,"orange")
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# The type doubles as the constructor function for values of that type
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sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire")
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sherekhan = typeof(tigger)(5.6, "fire") # => Tiger(5.6,"fire")
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# These struct-style types are called concrete types
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# They can be instantiated, but cannot have subtypes.
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@ -588,19 +588,19 @@ supertype(DirectIndexString) # => AbstractString
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# <: is the subtyping operator
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type Lion <: Cat # Lion is a subtype of Cat
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mane_color
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roar::AbstractString
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mane_color
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roar::AbstractString
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end
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# You can define more constructors for your type
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# Just define a function of the same name as the type
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# and call an existing constructor to get a value of the correct type
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Lion(roar::AbstractString) = Lion("green",roar)
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Lion(roar::AbstractString) = Lion("green", roar)
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# This is an outer constructor because it's outside the type definition
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type Panther <: Cat # Panther is also a subtype of Cat
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eye_color
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Panther() = new("green")
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eye_color
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Panther() = new("green")
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# Panthers will only have this constructor, and no default constructor.
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end
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# Using inner constructors, like Panther does, gives you control
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@ -619,30 +619,30 @@ end
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# Definitions for Lion, Panther, Tiger
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function meow(animal::Lion)
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animal.roar # access type properties using dot notation
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animal.roar # access type properties using dot notation
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end
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function meow(animal::Panther)
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"grrr"
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"grrr"
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end
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function meow(animal::Tiger)
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"rawwwr"
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"rawwwr"
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end
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# Testing the meow function
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meow(tigger) # => "rawwr"
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meow(Lion("brown","ROAAR")) # => "ROAAR"
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meow(Lion("brown", "ROAAR")) # => "ROAAR"
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meow(Panther()) # => "grrr"
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# Review the local type hierarchy
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issubtype(Tiger,Cat) # => false
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issubtype(Lion,Cat) # => true
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issubtype(Panther,Cat) # => true
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issubtype(Tiger, Cat) # => false
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issubtype(Lion, Cat) # => true
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issubtype(Panther, Cat) # => true
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# Defining a function that takes Cats
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function pet_cat(cat::Cat)
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println("The cat says $(meow(cat))")
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println("The cat says $(meow(cat))")
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end
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pet_cat(Lion("42")) # => prints "The cat says 42"
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@ -657,47 +657,47 @@ end
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# In Julia, all of the argument types contribute to selecting the best method.
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# Let's define a function with more arguments, so we can see the difference
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function fight(t::Tiger,c::Cat)
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println("The $(t.coatcolor) tiger wins!")
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function fight(t::Tiger, c::Cat)
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println("The $(t.coatcolor) tiger wins!")
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end
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# => fight (generic function with 1 method)
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fight(tigger,Panther()) # => prints The orange tiger wins!
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fight(tigger,Lion("ROAR")) # => prints The orange tiger wins!
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fight(tigger, Panther()) # => prints The orange tiger wins!
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fight(tigger, Lion("ROAR")) # => prints The orange tiger wins!
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# Let's change the behavior when the Cat is specifically a Lion
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fight(t::Tiger,l::Lion) = println("The $(l.mane_color)-maned lion wins!")
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fight(t::Tiger, l::Lion) = println("The $(l.mane_color)-maned lion wins!")
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# => fight (generic function with 2 methods)
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fight(tigger,Panther()) # => prints The orange tiger wins!
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fight(tigger,Lion("ROAR")) # => prints The green-maned lion wins!
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fight(tigger, Panther()) # => prints The orange tiger wins!
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fight(tigger, Lion("ROAR")) # => prints The green-maned lion wins!
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# We don't need a Tiger in order to fight
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fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))")
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fight(l::Lion, c::Cat) = println("The victorious cat says $(meow(c))")
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# => fight (generic function with 3 methods)
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fight(Lion("balooga!"),Panther()) # => prints The victorious cat says grrr
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fight(Lion("balooga!"), Panther()) # => prints The victorious cat says grrr
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try
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fight(Panther(),Lion("RAWR"))
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fight(Panther(), Lion("RAWR"))
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catch e
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println(e)
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println(e)
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# => MethodError(fight, (Panther("green"), Lion("green", "RAWR")), 0x000000000000557b)
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end
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# Also let the cat go first
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fight(c::Cat,l::Lion) = println("The cat beats the Lion")
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fight(c::Cat, l::Lion) = println("The cat beats the Lion")
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# This warning is because it's unclear which fight will be called in:
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try
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fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr
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fight(Lion("RAR"), Lion("brown", "rarrr")) # => prints The victorious cat says rarrr
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catch e
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println(e)
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println(e)
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# => MethodError(fight, (Lion("green", "RAR"), Lion("brown", "rarrr")), 0x000000000000557c)
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end
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# The result may be different in other versions of Julia
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fight(l::Lion,l2::Lion) = println("The lions come to a tie")
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fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The lions come to a tie
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fight(l::Lion, l2::Lion) = println("The lions come to a tie")
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fight(Lion("RAR"), Lion("brown", "rarrr")) # => prints The lions come to a tie
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# Under the hood
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