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-rw-r--r--julia.html.markdown317
1 files changed, 194 insertions, 123 deletions
diff --git a/julia.html.markdown b/julia.html.markdown
index dfa3103c..416f1a5a 100644
--- a/julia.html.markdown
+++ b/julia.html.markdown
@@ -89,7 +89,9 @@ false
# Strings are UTF8 encoded. Only if they contain only ASCII characters can
# they be safely indexed.
-ascii("This is a string")[1] # => 'T' # Julia indexes from 1
+ascii("This is a string")[1]
+# => 'T': ASCII/Unicode U+0054 (category Lu: Letter, uppercase)
+# Julia indexes from 1
# Otherwise, iterating over strings is recommended (map, for loops, etc).
# $ can be used for string interpolation:
@@ -101,7 +103,7 @@ using Printf
@printf "%d is less than %f\n" 4.5 5.3 # => 5 is less than 5.300000
# Printing is easy
-println("I'm Julia. Nice to meet you!")
+println("I'm Julia. Nice to meet you!") # => I'm Julia. Nice to meet you!
# String can be compared lexicographically
"good" > "bye" # => true
@@ -147,19 +149,18 @@ 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 Array{Int64,1}
# 1-dimensional array literals can be written with comma-separated values.
-b = [4, 5, 6] # => 3-element Int64 Array: [4, 5, 6]
-b = [4; 5; 6] # => 3-element Int64 Array: [4, 5, 6]
-b[1] # => 4
+b = [4, 5, 6] # => 3-element Array{Int64,1}: [4, 5, 6]
+b = [4; 5; 6] # => 3-element Array{Int64,1}: [4, 5, 6]
b[end] # => 6
# 2-dimensional 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] # => 2×2 Array{Int64,2}: [1 2; 3 4]
# Arrays of a particular type
-b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6]
+b = Int8[4, 5, 6] # => 3-element Array{Int8,1}: [4, 5, 6]
# Add stuff to the end of a list with push! and append!
push!(a, 1) # => [1]
@@ -186,16 +187,28 @@ pushfirst!(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 Array{Int64,1}: [5,4,6]
# Looking out of bounds is a BoundsError
try
- a[0]
- # => BoundsError: attempt to access 7-element Array{Int64,1} at index [0]
- a[end + 1]
- # => BoundsError: attempt to access 7-element Array{Int64,1} at index [8]
+ a[0]
+ # => ERROR: BoundsError: attempt to access 7-element Array{Int64,1} at
+ # index [0]
+ # => Stacktrace:
+ # => [1] getindex(::Array{Int64,1}, ::Int64) at .\array.jl:731
+ # => [2] top-level scope at none:0
+ # => [3] ...
+ # => in expression starting at ...\LearnJulia.jl:180
+ a[end + 1]
+ # => ERROR: BoundsError: attempt to access 7-element Array{Int64,1} at
+ # index [8]
+ # => Stacktrace:
+ # => [1] getindex(::Array{Int64,1}, ::Int64) at .\array.jl:731
+ # => [2] top-level scope at none:0
+ # => [3] ...
+ # => in expression starting at ...\LearnJulia.jl:188
catch e
println(e)
end
@@ -205,7 +218,8 @@ end
# 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 Array{Int64,1}: [1,2,3,4,5]
+a2 = [1:5] # => 1-element Array{UnitRange{Int64},1}: [1:5]
# You can look at ranges with slice syntax.
a[1:3] # => [1, 2, 3]
@@ -229,7 +243,9 @@ length(a) # => 8
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: MethodError: no method matching
+ # setindex!(::Tuple{Int64,Int64,Int64}, ::Int64, ::Int64)
catch e
println(e)
end
@@ -254,11 +270,12 @@ 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} with 0 entries
# You can create a dictionary using a literal
filled_dict = Dict("one" => 1, "two" => 2, "three" => 3)
-# => Dict{String,Int64}
+# => Dict{String,Int64} with 3 entries:
+# => "two" => 2, "one" => 1, "three" => 3
# Look up values with []
filled_dict["one"] # => 1
@@ -266,12 +283,13 @@ filled_dict["one"] # => 1
# Get all keys
keys(filled_dict)
# => Base.KeySet for a Dict{String,Int64} with 3 entries. Keys:
-# "two", "one", "three"
+# => "two", "one", "three"
# Note - dictionary keys are not sorted or in the order you inserted them.
# Get all values
values(filled_dict)
-# => Base.ValueIterator{Dict{String,Int64}} with 3 entries. Values: 2, 1, 3
+# => Base.ValueIterator for a Dict{String,Int64} with 3 entries. Values:
+# => 2, 1, 3
# Note - Same as above regarding key ordering.
# Check for existence of keys in a dictionary with in, haskey
@@ -282,7 +300,7 @@ haskey(filled_dict, 1) # => false
# Trying to look up a non-existent key will raise an error
try
- filled_dict["four"] # => KeyError: key "four" not found
+ filled_dict["four"] # => ERROR: KeyError: key "four" not found
catch e
println(e)
end
@@ -293,7 +311,7 @@ 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([4, 2, 3, 1])
@@ -353,18 +371,16 @@ for pair in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
from, to = pair
println("$from is a $to")
end
-# prints:
-# dog is a mammal
-# cat is a mammal
-# mouse is a mammal
+# => mouse is a mammal
+# => cat is a mammal
+# => dog is a mammal
for (k, v) in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
println("$k is a $v")
end
-# prints:
-# dog is a mammal
-# cat is a mammal
-# mouse is a mammal
+# => mouse is a mammal
+# => cat is a mammal
+# => dog is a mammal
# While loops loop while a condition is true
let x = 0
@@ -406,11 +422,11 @@ end
add(5, 6) # => 11 after printing out "x is 5 and y is 6"
# Compact assignment of functions
-f_add(x, y) = x + y # => "f (generic function with 1 method)"
+f_add(x, y) = x + y # => f_add (generic function with 1 method)
f_add(3, 4) # => 7
# Function can also return multiple values as tuple
-fn(x, y) = x + y, x - y
+fn(x, y) = x + y, x - y # => fn (generic function with 1 method)
fn(3, 4) # => (7, -1)
# You can define functions that take a variable number of
@@ -437,13 +453,14 @@ add(x...) # this is equivalent to add(5,6)
function defaults(a, b, x=5, y=6)
return "$a $b and $x $y"
end
+# => defaults (generic function with 3 methods)
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: MethodError: no method matching defaults(::Char)
+ defaults() # => ERROR: MethodError: no method matching defaults()
catch e
println(e)
end
@@ -452,10 +469,11 @@ end
function keyword_args(;k1=4, name2="hello") # note the ;
return Dict("k1" => k1, "name2" => name2)
end
+# => keyword_args (generic function with 1 method)
-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") # => ["name2"=>"hello", "k1"=>"mine"]
+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")
@@ -463,6 +481,7 @@ function all_the_args(normal_arg, optional_positional_arg=2; keyword_arg="foo")
println("optional arg: $optional_positional_arg")
println("keyword arg: $keyword_arg")
end
+# => all_the_args (generic function with 2 methods)
all_the_args(1, 3, keyword_arg=4)
# prints:
@@ -477,6 +496,7 @@ function create_adder(x)
end
return adder
end
+# => create_adder (generic function with 1 method)
# This is "stabby lambda syntax" for creating anonymous functions
(x -> x > 2)(3) # => true
@@ -485,6 +505,7 @@ end
function create_adder(x)
y -> x + y
end
+# => create_adder (generic function with 1 method)
# You can also name the internal function, if you want
function create_adder(x)
@@ -493,9 +514,11 @@ function create_adder(x)
end
adder
end
+# => create_adder (generic function with 1 method)
-add_10 = create_adder(10)
-add_10(3) # => 13
+add_10 = create_adder(10) # => (::getfield(Main, Symbol("#adder#11")){Int64})
+ # (generic function with 1 method)
+add_10(3) # => 13
# There are built-in higher order functions
@@ -555,16 +578,16 @@ abstract type Cat end # just a name and point in the type hierarchy
using InteractiveUtils # defines the subtype and supertype function
# For example, Number is an abstract type
subtypes(Number) # => 2-element Array{Any,1}:
- # Complex{T<:Real}
- # Real
+ # => Complex
+ # => Real
subtypes(Cat) # => 0-element Array{Any,1}
# AbstractString, as the name implies, is also an abstract type
-subtypes(AbstractString) # 4-element Array{Any,1}:
- # String
- # SubString
- # SubstitutionString
- # Test.GenericString
+subtypes(AbstractString) # => 4-element Array{Any,1}:
+ # => String
+ # => SubString
+ # => SubstitutionString
+ # => Test.GenericString
# Every type has a super type; use the `supertype` function to get it.
typeof(5) # => Int64
@@ -626,7 +649,7 @@ function meow(animal::Tiger)
end
# Testing the meow function
-meow(tigger) # => "rawwr"
+meow(tigger) # => "rawwwr"
meow(Lion("brown", "ROAAR")) # => "ROAAR"
meow(Panther()) # => "grrr"
@@ -639,10 +662,11 @@ Panther <: Cat # => true
function pet_cat(cat::Cat)
println("The cat says $(meow(cat))")
end
+# => pet_cat (generic function with 1 method)
-pet_cat(Lion("42")) # => prints "The cat says 42"
+pet_cat(Lion("42")) # => The cat says 42
try
- pet_cat(tigger) # => ERROR: no method pet_cat(Tiger,)
+ pet_cat(tigger) # => ERROR: MethodError: no method matching pet_cat(::Tiger)
catch e
println(e)
end
@@ -657,45 +681,54 @@ function fight(t::Tiger, c::Cat)
end
# => 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()) # => The orange tiger wins!
+fight(tigger, Lion("ROAR")) # => 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(tigger, Panther()) # => prints The orange tiger wins!
-fight(tigger, Lion("ROAR")) # => prints The green-maned lion wins!
+fight(tigger, Panther()) # => The orange tiger wins!
+fight(tigger, Lion("ROAR")) # => 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(Lion("balooga!"), Panther()) # => prints The victorious cat says grrr
+fight(Lion("balooga!"), Panther()) # => The victorious cat says grrr
try
- fight(Panther(), Lion("RAWR"))
+ fight(Panther(), Lion("RAWR"))
+ # => ERROR: MethodError: no method matching fight(::Panther, ::Lion)
+ # => Closest candidates are:
+ # => fight(::Tiger, ::Lion) at ...
+ # => fight(::Tiger, ::Cat) at ...
+ # => fight(::Lion, ::Cat) at ...
+ # => ...
catch e
println(e)
- # => MethodError(fight, (Panther("green"), Lion("green", "RAWR")),
- # 0x000000000000557b)
end
# Also let the cat go first
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:
try
fight(Lion("RAR"), Lion("brown", "rarrr"))
- # => prints The victorious cat says rarrr
+ # => ERROR: MethodError: fight(::Lion, ::Lion) is ambiguous. Candidates:
+ # => fight(c::Cat, l::Lion) in Main at ...
+ # => fight(l::Lion, c::Cat) in Main at ...
+ # => Possible fix, define
+ # => fight(::Lion, ::Lion)
+ # => ...
catch e
println(e)
- # => MethodError(fight, (Lion("green", "RAR"), Lion("brown", "rarrr")),
- # 0x000000000000557c)
end
# 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(l::Lion, l2::Lion) = println("The lions come to a tie")
+# => fight (generic function with 5 methods)
+fight(Lion("RAR"), Lion("brown", "rarrr")) # => The lions come to a tie
# Under the hood
@@ -706,74 +739,112 @@ square_area(l) = l * l # square_area (generic function with 1 method)
square_area(5) # => 25
# What happens when we feed square_area an integer?
-code_native(square_area, (Int32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1 # Prologue
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # movsxd RAX, EDI # Fetch l from memory?
- # imul RAX, RAX # Square l and store the result in RAX
- # pop RBP # Restore old base pointer
- # ret # Result will still be in RAX
-
-code_native(square_area, (Float32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vmulss XMM0, XMM0, XMM0 # Scalar single precision multiply (AVX)
- # pop RBP
- # ret
-
-code_native(square_area, (Float64,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vmulsd XMM0, XMM0, XMM0 # Scalar double precision multiply (AVX)
- # pop RBP
- # ret
- #
+code_native(square_area, (Int32,), syntax = :intel)
+ # .text
+ # ; Function square_area {
+ # ; Location: REPL[116]:1 # Prologue
+ # push rbp
+ # mov rbp, rsp
+ # ; Function *; {
+ # ; Location: int.jl:54
+ # imul ecx, ecx # Square l and store the result in ECX
+ # ;}
+ # mov eax, ecx
+ # pop rbp # Restore old base pointer
+ # ret # Result will still be in EAX
+ # nop dword ptr [rax + rax]
+ # ;}
+
+code_native(square_area, (Float32,), syntax = :intel)
+ # .text
+ # ; Function square_area {
+ # ; Location: REPL[116]:1
+ # push rbp
+ # mov rbp, rsp
+ # ; Function *; {
+ # ; Location: float.jl:398
+ # vmulss xmm0, xmm0, xmm0 # Scalar single precision multiply (AVX)
+ # ;}
+ # pop rbp
+ # ret
+ # nop word ptr [rax + rax]
+ # ;}
+
+code_native(square_area, (Float64,), syntax = :intel)
+ # .text
+ # ; Function square_area {
+ # ; Location: REPL[116]:1
+ # push rbp
+ # mov rbp, rsp
+ # ; Function *; {
+ # ; Location: float.jl:399
+ # vmulsd xmm0, xmm0, xmm0 # Scalar double precision multiply (AVX)
+ # ;}
+ # pop rbp
+ # ret
+ # nop word ptr [rax + rax]
+ # ;}
+
# Note that julia will use floating point instructions if any of the
# arguments are floats.
# Let's calculate the area of a circle
circle_area(r) = pi * r * r # circle_area (generic function with 1 method)
circle_area(5) # 78.53981633974483
-code_native(circle_area, (Int32,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # Source line: 1
- # vcvtsi2sd XMM0, XMM0, EDI # Load integer (r) from memory
- # movabs RAX, 4593140240 # Load pi
- # vmulsd XMM1, XMM0, QWORD PTR [RAX] # pi * r
- # vmulsd XMM0, XMM0, XMM1 # (pi * r) * r
- # pop RBP
- # ret
- #
-
-code_native(circle_area, (Float64,))
- # .section __TEXT,__text,regular,pure_instructions
- # Filename: none
- # Source line: 1
- # push RBP
- # mov RBP, RSP
- # movabs RAX, 4593140496
- # Source line: 1
- # vmulsd XMM1, XMM0, QWORD PTR [RAX]
- # vmulsd XMM0, XMM1, XMM0
- # pop RBP
- # ret
- #
+code_native(circle_area, (Int32,), syntax = :intel)
+ # .text
+ # ; Function circle_area {
+ # ; Location: REPL[121]:1
+ # push rbp
+ # mov rbp, rsp
+ # ; Function *; {
+ # ; Location: operators.jl:502
+ # ; Function *; {
+ # ; Location: promotion.jl:314
+ # ; Function promote; {
+ # ; Location: promotion.jl:284
+ # ; Function _promote; {
+ # ; Location: promotion.jl:261
+ # ; Function convert; {
+ # ; Location: number.jl:7
+ # ; Function Type; {
+ # ; Location: float.jl:60
+ # vcvtsi2sd xmm0, xmm0, ecx # Load integer (r) from memory
+ # movabs rax, 497710928 # Load pi
+ # ;}}}}}
+ # ; Function *; {
+ # ; Location: float.jl:399
+ # vmulsd xmm1, xmm0, qword ptr [rax] # pi * r
+ # vmulsd xmm0, xmm1, xmm0 # (pi * r) * r
+ # ;}}
+ # pop rbp
+ # ret
+ # nop dword ptr [rax]
+ # ;}
+
+code_native(circle_area, (Float64,), syntax = :intel)
+ # .text
+ # ; Function circle_area {
+ # ; Location: REPL[121]:1
+ # push rbp
+ # mov rbp, rsp
+ # movabs rax, 497711048
+ # ; Function *; {
+ # ; Location: operators.jl:502
+ # ; Function *; {
+ # ; Location: promotion.jl:314
+ # ; Function *; {
+ # ; Location: float.jl:399
+ # vmulsd xmm1, xmm0, qword ptr [rax]
+ # ;}}}
+ # ; Function *; {
+ # ; Location: float.jl:399
+ # vmulsd xmm0, xmm1, xmm0
+ # ;}
+ # pop rbp
+ # ret
+ # nop dword ptr [rax + rax]
+ # ;}
```
## Further Reading