one more quick run over the code

This commit is contained in:
Martijn Visser 2018-08-15 16:54:03 +02:00
parent c8ad0d0809
commit 9fab30a26a

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@ -30,7 +30,7 @@ This is based on Julia 1.0.0
3 # => 3 (Int64) 3 # => 3 (Int64)
3.2 # => 3.2 (Float64) 3.2 # => 3.2 (Float64)
2 + 1im # => 2 + 1im (Complex{Int64}) 2 + 1im # => 2 + 1im (Complex{Int64})
2 // 3 # => 2//3 (Rational{Int64}) 2 // 3 # => 2 // 3 (Rational{Int64})
# All of the normal infix operators are available. # All of the normal infix operators are available.
1 + 1 # => 2 1 + 1 # => 2
@ -81,29 +81,18 @@ false
2 < 3 < 2 # => false 2 < 3 < 2 # => false
# Strings are created with " # Strings are created with "
try "This is a string."
"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 ' # Character literals are written with '
try 'a'
'a'
catch ; end
# Some strings can be indexed like an array of characters # Strings are UTF8 encoded. Only if they contain only ASCII characters can
try # they be safely indexed.
"This is a string"[1] # => 'T' # Julia indexes from 1 ascii("This is a string")[1] # => 'T' # Julia indexes from 1
catch ; end # Otherwise, iterating over strings is recommended (map, for loops, etc).
# 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: # $ can be used for string interpolation:
try "2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
"2 + 2 = $(2 + 2)" # => "2 + 2 = 4"
catch ; end
# You can put any Julia expression inside the parentheses. # You can put any Julia expression inside the parentheses.
# Another way to format strings is the printf macro from the stdlib Printf. # Another way to format strings is the printf macro from the stdlib Printf.
@ -168,7 +157,7 @@ b[end] # => 6
# 2-dimensional arrays use space-separated values and semicolon-separated rows. # 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] # => 2x2 Int64 Array: [1 2; 3 4]
# Arrays of a particular Type # Arrays of a particular type
b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6] b = Int8[4, 5, 6] # => 3-element Int8 Array: [4, 5, 6]
# Add stuff to the end of a list with push! and append! # Add stuff to the end of a list with push! and append!
@ -202,15 +191,17 @@ sort!(arr) # => [4,5,6]; arr is now [4,5,6]
# Looking out of bounds is a BoundsError # Looking out of bounds is a BoundsError
try try
a[0] # => ERROR: BoundsError() in getindex at array.jl:270 a[0]
a[end + 1] # => ERROR: BoundsError() in getindex at array.jl:270 # => 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]
catch e catch e
println(e) println(e)
end end
# Errors list the line and file they came from, even if it's in the standard # Errors list the line and file they came from, even if it's in the standard
# library. If you built Julia from source, you can look in the folder base # library. You can look in the folder share/julia inside the julia folder to
# inside the julia folder to find these files. # find these files.
# You can initialize arrays from ranges # 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]
@ -242,7 +233,7 @@ catch e
println(e) println(e)
end end
# Many list functions also work on tuples # Many array functions also work on tuples
length(tup) # => 3 length(tup) # => 3
tup[1:2] # => (1,2) tup[1:2] # => (1,2)
in(2, tup) # => true in(2, tup) # => true
@ -266,19 +257,20 @@ empty_dict = Dict() # => Dict{Any,Any}()
# You can create a dictionary using a literal # You can create a dictionary using a literal
filled_dict = Dict("one" => 1, "two" => 2, "three" => 3) filled_dict = Dict("one" => 1, "two" => 2, "three" => 3)
# => Dict{ASCIIString,Int64} # => Dict{String,Int64}
# Look up values with [] # Look up values with []
filled_dict["one"] # => 1 filled_dict["one"] # => 1
# Get all keys # Get all keys
keys(filled_dict) keys(filled_dict)
# => KeyIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2]) # => Base.KeySet for a Dict{String,Int64} with 3 entries. Keys:
# "two", "one", "three"
# Note - dictionary keys are not sorted or in the order you inserted them. # Note - dictionary keys are not sorted or in the order you inserted them.
# Get all values # Get all values
values(filled_dict) values(filled_dict)
# => ValueIterator{Dict{ASCIIString,Int64}}(["three"=>3,"one"=>1,"two"=>2]) # => Base.ValueIterator{Dict{String,Int64}} with 3 entries. Values: 2, 1, 3
# Note - Same as above regarding key ordering. # Note - Same as above regarding key ordering.
# Check for existence of keys in a dictionary with in, haskey # Check for existence of keys in a dictionary with in, haskey
@ -289,33 +281,33 @@ haskey(filled_dict, 1) # => false
# Trying to look up a non-existent key will raise an error # Trying to look up a non-existent key will raise an error
try try
filled_dict["four"] # => ERROR: key not found: four in getindex at dict.jl:489 filled_dict["four"] # => KeyError: key "four" not found
catch e catch e
println(e) println(e)
end end
# Use the get method to avoid that error by providing a default value # Use the get method to avoid that error by providing a default value
# get(dictionary,key,default_value) # get(dictionary, key, default_value)
get(filled_dict, "one", 4) # => 1 get(filled_dict, "one", 4) # => 1
get(filled_dict, "four", 4) # => 4 get(filled_dict, "four", 4) # => 4
# Use Sets to represent collections of unordered, unique values # Use Sets to represent collections of unordered, unique values
empty_set = Set() # => Set{Any}() empty_set = Set() # => Set{Any}()
# Initialize a set with values # 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([4, 2, 3, 1])
# Add more values to a set # Add more values to a set
push!(filled_set, 5) # => Set{Int64}(5,4,2,3,1) push!(filled_set, 5) # => Set([4, 2, 3, 5, 1])
# Check if the values are in the set # Check if the values are in the set
in(2, filled_set) # => true in(2, filled_set) # => true
in(10, filled_set) # => false in(10, filled_set) # => false
# There are functions for set intersection, union, and difference. # There are functions for set intersection, union, and difference.
other_set = Set([3, 4, 5, 6]) # => Set{Int64}(6,4,5,3) other_set = Set([3, 4, 5, 6]) # => Set([4, 3, 5, 6])
intersect(filled_set, other_set) # => Set{Int64}(3,4,5) intersect(filled_set, other_set) # => Set([4, 3, 5])
union(filled_set, other_set) # => Set{Int64}(1,2,3,4,5,6) union(filled_set, other_set) # => Set([4, 2, 3, 5, 6, 1])
setdiff(Set([1,2,3,4]), Set([2,3,5])) # => Set{Int64}(1,4) setdiff(Set([1,2,3,4]), Set([2,3,5])) # => Set([4, 1])
#################################################### ####################################################
@ -356,8 +348,9 @@ end
# cat is a mammal # cat is a mammal
# mouse is a mammal # mouse is a mammal
for a in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal") for pair in Dict("dog" => "mammal", "cat" => "mammal", "mouse" => "mammal")
println("$(a[1]) is a $(a[2])") from, to = pair
println("$from is a $to")
end end
# prints: # prints:
# dog is a mammal # dog is a mammal
@ -705,7 +698,7 @@ fight(Lion("RAR"), Lion("brown", "rarrr")) # => prints The lions come to a tie
square_area(l) = l * l # square_area (generic function with 1 method) square_area(l) = l * l # square_area (generic function with 1 method)
square_area(5) #25 square_area(5) # => 25
# What happens when we feed square_area an integer? # What happens when we feed square_area an integer?
code_native(square_area, (Int32,)) code_native(square_area, (Int32,))