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Diffstat (limited to 'julia.html.markdown')
| -rw-r--r-- | julia.html.markdown | 87 |
1 files changed, 47 insertions, 40 deletions
diff --git a/julia.html.markdown b/julia.html.markdown index 9e28452f..047bb538 100644 --- a/julia.html.markdown +++ b/julia.html.markdown @@ -3,13 +3,14 @@ language: Julia contributors: - ["Leah Hanson", "http://leahhanson.us"] - ["Pranit Bauva", "http://github.com/pranitbauva1997"] + - ["Daniel YC Lin", "http://github.com/dlintw"] filename: learnjulia.jl --- Julia is a new homoiconic functional language focused on technical computing. While having the full power of homoiconic macros, first-class functions, and low-level control, Julia is as easy to learn and use as Python. -This is based on Julia 0.4. +This is based on Julia 0.6.4 ```ruby @@ -49,7 +50,7 @@ div(5, 2) # => 2 # for a truncated result, use div ~2 # => -3 # bitwise not 3 & 5 # => 1 # bitwise and 2 | 4 # => 6 # bitwise or -2 $ 4 # => 6 # bitwise xor +xor(2, 4) # => 6 # bitwise xor 2 >>> 1 # => 1 # logical shift right 2 >> 1 # => 1 # arithmetic shift right 2 << 1 # => 4 # logical/arithmetic shift left @@ -80,25 +81,33 @@ false 2 < 3 < 2 # => false # Strings are created with " +try "This is a string." +catch ; end # Julia has several types of strings, including ASCIIString and UTF8String. # More on this in the Types section. # Character literals are written with ' +try 'a' +catch ; end # Some strings can be indexed like an array of characters +try "This is a string"[1] # => 'T' # Julia indexes from 1 +catch ; end # 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: +try "2 + 2 = $(2 + 2)" # => "2 + 2 = 4" +catch ; end # You can put any Julia expression inside the parentheses. # Another way to format strings is the printf macro. -@printf "%d is less than %f" 4.5 5.3 # 4.5 is less than 5.300000 +@printf "%d is less than %f" 4.5 5.3 # 4 is less than 5.300000 # Printing is easy println("I'm Julia. Nice to meet you!") @@ -405,8 +414,8 @@ f_add(x, y) = x + y # => "f (generic function with 1 method)" f_add(3, 4) # => 7 # Function can also return multiple values as tuple -f(x, y) = x + y, x - y -f(3, 4) # => (7, -1) +fn(x, y) = x + y, x - y +fn(3, 4) # => (7, -1) # You can define functions that take a variable number of # positional arguments @@ -497,9 +506,10 @@ add_10(3) # => 13 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 +# We can use list comprehensions [add_10(i) for i=[1, 2, 3]] # => [11, 12, 13] [add_10(i) for i in [1, 2, 3]] # => [11, 12, 13] +[x for x in [3, 4, 5, 6, 7] if x > 5] # => [6, 7] #################################################### ## 5. Types @@ -543,7 +553,7 @@ sherekhan = typeof(tigger)(5.6,"fire") # => Tiger(5.6,"fire") # The other kind of types is abstract types. # abstract Name -abstract Cat # just a name and point in the type hierarchy +abstract type Cat end # 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 @@ -553,30 +563,28 @@ subtypes(Number) # => 2-element Array{Any,1}: subtypes(Cat) # => 0-element Array{Any,1} # AbstractString, as the name implies, is also an abstract type -subtypes(AbstractString) # 8-element Array{Any,1}: - # Base.SubstitutionString{T<:AbstractString} - # DirectIndexString - # RepString - # RevString{T<:AbstractString} - # RopeString - # SubString{T<:AbstractString} - # UTF16String - # UTF8String - -# Every type has a super type; use the `super` function to get it. +subtypes(AbstractString) # 6-element Array{Union{DataType, UnionAll},1}: + # Base.SubstitutionString + # Base.Test.GenericString + # DirectIndexString + # RevString + # String + # SubString + +# Every type has a super type; use the `supertype` function to get it. typeof(5) # => Int64 -super(Int64) # => Signed -super(Signed) # => Integer -super(Integer) # => Real -super(Real) # => Number -super(Number) # => Any -super(super(Signed)) # => Real -super(Any) # => Any +supertype(Int64) # => Signed +supertype(Signed) # => Integer +supertype(Integer) # => Real +supertype(Real) # => Number +supertype(Number) # => Any +supertype(supertype(Signed)) # => Real +supertype(Any) # => Any # All of these type, except for Int64, are abstract. -typeof("fire") # => ASCIIString -super(ASCIIString) # => DirectIndexString -super(DirectIndexString) # => AbstractString -# Likewise here with ASCIIString +typeof("fire") # => String +supertype(String) # => AbstractString +# Likewise here with String +supertype(DirectIndexString) # => AbstractString # <: is the subtyping operator type Lion <: Cat # Lion is a subtype of Cat @@ -670,23 +678,22 @@ fight(l::Lion,c::Cat) = println("The victorious cat says $(meow(c))") fight(Lion("balooga!"),Panther()) # => prints The victorious cat says grrr try - fight(Panther(),Lion("RAWR")) # => ERROR: no method fight(Panther,Lion) -catch + fight(Panther(),Lion("RAWR")) +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") -# => Warning: New definition -# fight(Cat,Lion) at none:1 -# is ambiguous with -# fight(Lion,Cat) at none:2. -# Make sure -# fight(Lion,Lion) -# is defined first. -#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 +try + fight(Lion("RAR"),Lion("brown","rarrr")) # => prints The victorious cat says rarrr +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") |