# Julia Notes Day2 -- string and collections ## Char and String A `Char` value represents a single character ```julia c = 'x' d = Int('x') # 120 e = Char(120) # 'x' f = '\u2200' # '∀': Unicode U+2200 (category Sm: Symbol, math) g = 'A' + 1 # 'B' ``` String literals are delimited by double quotes or triple double quotes (not single quotes). ```julia s = "\u2200 x \u2203 y" # "∀ x ∃ y" s *= "世界" # "∀ x ∃ y世界" length(s) # 9 sizeof(s) # 17 s[end] # '界': Unicode U+754C (category Lo: Letter, other) findfirst('界',s) # 15 # Sequential iteration is implemented by the iterate function. # The general for loop: for c in s print(c*' ') end # ∀ x ∃ y 世 界 ``` > String literals are encoded using the UTF-8 encoding. UTF-8 is a variable-width encoding, meaning that not all characters are encoded in the same number of bytes ("code units"). In UTF-8, ASCII characters — i.e. those with code points less than 0x80 (128) – are encoded as they are in ASCII, using a single byte, while code points 0x80 and above are encoded using multiple bytes — up to four per character. > > String indices in Julia refer to code units (= bytes for UTF-8), the fixed-width building blocks that are used to encode arbitrary characters (code points). This means that not every index into a `String` is necessarily a valid index for a character. If you index into a string at such an invalid byte index, an error is thrown ```julia greet = "Hello"; whom = "world"; #Julia provides * for string concatenation greet * ' ' * whom # "Hello world" #interpolation into string literals using $ "$greet, $whom." # "Hello, world." # triple-quoted strings are dedented to the level of the least-indented line. str = """ Hello, world. """ # " Hello,\n world.\n" "1 + 2 = 3" == "1 + 2 = $(1 + 2)" # true # repeat("A", 10) 'A'^10 # "AAAAAAAAAA" "B"^10 # "BBBBBBBBBB" "BA"^10 # "BABABABABABABABABABA" ``` ## Range and Vector ```julia V = [i/2 for i in 1:10] # Comprehensions can also be written without the enclosing square brackets, # producing an object known as a generator. sum(1/n^2 for n=1:1000) # convert a range to a vector by using the collect function. vec = collect(1:2:7) println(vec) # Output: [1, 3, 5, 7] ``` ## Matrix ```julia A = [1 2; 3 4] #= 2×2 Matrix{Int64}: 1 2 3 4 =# B = A*A*A #= 2×2 Matrix{Int64}: 37 54 81 118 =# B == A^3 # true C = A * 3 C == 3A # true sin.(A) #= 2×2 Matrix{Float64}: 0.841471 0.909297 0.14112 -0.756802 =# sin(A) #= 2×2 Matrix{Float64}: -0.465581 -0.148424 -0.222637 -0.688218 =# A*[1,2] #= 2-element Vector{Int64}: 5 11 =# ``` ## Dict ```julia Dict("A"=>1, "B"=>2) #= Dict{String, Int64} with 2 entries: "B" => 2 "A" => 1 =# ``` ## List of functions of Collections > * [Base.iterate — Function](https://docs.julialang.org/en/v1/base/collections/#Base.iterate) > > * [Base.IteratorSize — Type](https://docs.julialang.org/en/v1/base/collections/#Base.IteratorSize) > > * [Base.IteratorEltype — Type](https://docs.julialang.org/en/v1/base/collections/#Base.IteratorEltype) > > * [Base.AbstractRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.AbstractRange) > > * [Base.OrdinalRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.OrdinalRange) > > * [Base.AbstractUnitRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.AbstractUnitRange) > > * [Base.StepRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.StepRange) > > * [Base.UnitRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.UnitRange) > > * [Base.LinRange — Type](https://docs.julialang.org/en/v1/base/collections/#Base.LinRange) > > * [Base.isempty — Function](https://docs.julialang.org/en/v1/base/collections/#Base.isempty) > > * [Base.empty! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.empty!) > > * [Base.length — Function](https://docs.julialang.org/en/v1/base/collections/#Base.length) > > * [Base.checked\_length — Function](https://docs.julialang.org/en/v1/base/collections/#Base.checked_length) > > * [Base.in — Function](https://docs.julialang.org/en/v1/base/collections/#Base.in) > > * [Base.:∉ — Function](https://docs.julialang.org/en/v1/base/collections/#Base.:%E2%88%89) > > * [Base.eltype — Function](https://docs.julialang.org/en/v1/base/collections/#Base.eltype) > > * [Base.indexin — Function](https://docs.julialang.org/en/v1/base/collections/#Base.indexin) > > * [Base.unique — Function](https://docs.julialang.org/en/v1/base/collections/#Base.unique) > > * [Base.unique! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.unique!) > > * [Base.allunique — Function](https://docs.julialang.org/en/v1/base/collections/#Base.allunique) > > * [Base.allequal — Function](https://docs.julialang.org/en/v1/base/collections/#Base.allequal) > > * [Base.reduce — Method](https://docs.julialang.org/en/v1/base/collections/#Base.reduce-Tuple{Any,20%Any}) > > * [Base.reduce — Method](https://docs.julialang.org/en/v1/base/collections/#Base.reduce-Tuple{Any,20%AbstractArray}) > > * [Base.foldl — Method](https://docs.julialang.org/en/v1/base/collections/#Base.foldl-Tuple{Any,20%Any}) > > * [Base.foldr — Method](https://docs.julialang.org/en/v1/base/collections/#Base.foldr-Tuple{Any,20%Any}) > > * [Base.maximum — Function](https://docs.julialang.org/en/v1/base/collections/#Base.maximum) > > * [Base.maximum! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.maximum!) > > * [Base.minimum — Function](https://docs.julialang.org/en/v1/base/collections/#Base.minimum) > > * [Base.minimum! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.minimum!) > > * [Base.extrema — Function](https://docs.julialang.org/en/v1/base/collections/#Base.extrema) > > * [Base.extrema! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.extrema!) > > * [Base.argmax — Function](https://docs.julialang.org/en/v1/base/collections/#Base.argmax) > > * [Base.argmin — Function](https://docs.julialang.org/en/v1/base/collections/#Base.argmin) > > * [Base.findmax — Function](https://docs.julialang.org/en/v1/base/collections/#Base.findmax) > > * [Base.findmin — Function](https://docs.julialang.org/en/v1/base/collections/#Base.findmin) > > * [Base.findmax! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.findmax!) > > * [Base.findmin! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.findmin!) > > * [Base.sum — Function](https://docs.julialang.org/en/v1/base/collections/#Base.sum) > > * [Base.sum! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.sum!) > > * [Base.prod — Function](https://docs.julialang.org/en/v1/base/collections/#Base.prod) > > * [Base.prod! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.prod!) > > * [Base.any — Method](https://docs.julialang.org/en/v1/base/collections/#Base.any-Tuple%7BAny%7D) > > * [Base.any — Method](https://docs.julialang.org/en/v1/base/collections/#Base.any-Tuple{AbstractArray,20%Any}) > > * [Base.any! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.any!) > > * [Base.all — Method](https://docs.julialang.org/en/v1/base/collections/#Base.all-Tuple%7BAny%7D) > > * [Base.all — Method](https://docs.julialang.org/en/v1/base/collections/#Base.all-Tuple{AbstractArray,20%Any}) > > * [Base.all! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.all!) > > * [Base.count — Function](https://docs.julialang.org/en/v1/base/collections/#Base.count) > > * [Base.foreach — Function](https://docs.julialang.org/en/v1/base/collections/#Base.foreach) > > * [Base.map — Function](https://docs.julialang.org/en/v1/base/collections/#Base.map) > > * [Base.map! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.map!) > > * [Base.mapreduce — Method](https://docs.julialang.org/en/v1/base/collections/#Base.mapreduce-Tuple{Any,%20Any,%20Any}) > > * [Base.mapfoldl — Method](https://docs.julialang.org/en/v1/base/collections/#Base.mapfoldl-Tuple{Any,%20Any,%20Any}) > > * [Base.mapfoldr — Method](https://docs.julialang.org/en/v1/base/collections/#Base.mapfoldr-Tuple{Any,%20Any,%20Any}) > > * [Base.first — Function](https://docs.julialang.org/en/v1/base/collections/#Base.first) > > * [Base.last — Function](https://docs.julialang.org/en/v1/base/collections/#Base.last) > > * [Base.front — Function](https://docs.julialang.org/en/v1/base/collections/#Base.front) > > * [Base.tail — Function](https://docs.julialang.org/en/v1/base/collections/#Base.tail) > > * [Base.step — Function](https://docs.julialang.org/en/v1/base/collections/#Base.step) > > * [Base.collect — Method](https://docs.julialang.org/en/v1/base/collections/#Base.collect-Tuple%7BAny%7D) > > * [Base.collect — Method](https://docs.julialang.org/en/v1/base/collections/#Base.collect-Tuple{Type,%20Any}) > > * [Base.filter — Function](https://docs.julialang.org/en/v1/base/collections/#Base.filter) > > * [Base.filter! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.filter!) > > * [Base.replace — Method](https://docs.julialang.org/en/v1/base/collections/#Base.replace-Tuple{Any,20%Vararg{Pair}}) > > * [Base.replace — Method](https://docs.julialang.org/en/v1/base/collections/#Base.replace-Tuple{Union{Function,%20Type},%20Any}) > > * [Base.replace! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.replace!) > > * [Base.rest — Function](https://docs.julialang.org/en/v1/base/collections/#Base.rest) > > * [Base.split\_rest — Function](https://docs.julialang.org/en/v1/base/collections/#Base.split_rest) > > * [Base.getindex — Function](https://docs.julialang.org/en/v1/base/collections/#Base.getindex) > > * [Base.setindex! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.setindex!) > > * [Base.firstindex — Function](https://docs.julialang.org/en/v1/base/collections/#Base.firstindex) > > * [Base.lastindex — Function](https://docs.julialang.org/en/v1/base/collections/#Base.lastindex) > > * [Base.AbstractDict — Type](https://docs.julialang.org/en/v1/base/collections/#Base.AbstractDict) > > * [Base.Dict — Type](https://docs.julialang.org/en/v1/base/collections/#Base.Dict) > > * [Base.IdDict — Type](https://docs.julialang.org/en/v1/base/collections/#Base.IdDict) > > * [Base.WeakKeyDict — Type](https://docs.julialang.org/en/v1/base/collections/#Base.WeakKeyDict) > > * [Base.ImmutableDict — Type](https://docs.julialang.org/en/v1/base/collections/#Base.ImmutableDict) > > * [Base.haskey — Function](https://docs.julialang.org/en/v1/base/collections/#Base.haskey) > > * [Base.get — Function](https://docs.julialang.org/en/v1/base/collections/#Base.get) > > * [Base.get! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.get!) > > * [Base.getkey — Function](https://docs.julialang.org/en/v1/base/collections/#Base.getkey) > > * [Base.delete! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.delete!) > > * [Base.pop! — Method](https://docs.julialang.org/en/v1/base/collections/#Base.pop!-Tuple{Any,%20Any,%20Any}) > > * [Base.keys — Function](https://docs.julialang.org/en/v1/base/collections/#Base.keys) > > * [Base.values — Function](https://docs.julialang.org/en/v1/base/collections/#Base.values) > > * [Base.pairs — Function](https://docs.julialang.org/en/v1/base/collections/#Base.pairs) > > * [Base.merge — Function](https://docs.julialang.org/en/v1/base/collections/#Base.merge) > > * [Base.mergewith — Function](https://docs.julialang.org/en/v1/base/collections/#Base.mergewith) > > * [Base.merge! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.merge!) > > * [Base.mergewith! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.mergewith!) > > * [Base.sizehint! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.sizehint!) > > * [Base.keytype — Function](https://docs.julialang.org/en/v1/base/collections/#Base.keytype) > > * [Base.valtype — Function](https://docs.julialang.org/en/v1/base/collections/#Base.valtype) > > * [Base.AbstractSet — Type](https://docs.julialang.org/en/v1/base/collections/#Base.AbstractSet) > > * [Base.Set — Type](https://docs.julialang.org/en/v1/base/collections/#Base.Set) > > * [Base.BitSet — Type](https://docs.julialang.org/en/v1/base/collections/#Base.BitSet) > > * [Base.union — Function](https://docs.julialang.org/en/v1/base/collections/#Base.union) > > * [Base.union! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.union!) > > * [Base.intersect — Function](https://docs.julialang.org/en/v1/base/collections/#Base.intersect) > > * [Base.setdiff — Function](https://docs.julialang.org/en/v1/base/collections/#Base.setdiff) > > * [Base.setdiff! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.setdiff!) > > * [Base.symdiff — Function](https://docs.julialang.org/en/v1/base/collections/#Base.symdiff) > > * [Base.symdiff! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.symdiff!) > > * [Base.intersect! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.intersect!) > > * [Base.issubset — Function](https://docs.julialang.org/en/v1/base/collections/#Base.issubset) > > * [Base.:⊈ — Function](https://docs.julialang.org/en/v1/base/collections/#Base.:%E2%8A%88) > > * [Base.:⊊ — Function](https://docs.julialang.org/en/v1/base/collections/#Base.:%E2%8A%8A) > > * [Base.issetequal — Function](https://docs.julialang.org/en/v1/base/collections/#Base.issetequal) > > * [Base.isdisjoint — Function](https://docs.julialang.org/en/v1/base/collections/#Base.isdisjoint) > > * [Base.push! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.push!) > > * [Base.pop! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.pop!) > > * [Base.popat! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.popat!) > > * [Base.pushfirst! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.pushfirst!) > > * [Base.popfirst! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.popfirst!) > > * [Base.insert! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.insert!) > > * [Base.deleteat! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.deleteat!) > > * [Base.keepat! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.keepat!) > > * [Base.splice! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.splice!) > > * [Base.resize! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.resize!) > > * [Base.append! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.append!) > > * [Base.prepend! — Function](https://docs.julialang.org/en/v1/base/collections/#Base.prepend!) > > * [Core.Pair — Type](https://docs.julialang.org/en/v1/base/collections/#Core.Pair) > > * [Base.Pairs — Type](https://docs.julialang.org/en/v1/base/collections/#Base.Pairs) >