julia lang - Immutable dictionary -

is there way enforce dictionary being constant?

i have function reads out file parameters (and ignores comments) , stores in dict:

function getparameters(filename::abstractstring)     f = open(filename,"r")     dict = dict{abstractstring, abstractstring}()     ln in eachline(f)         m = match(r"^\s*(?p<key>\w+)\s+(?p<value>[\w+-.]+)", ln)          if m != nothing             dict[m[:key]] = m[:value]         end     end     close(f)     return dict end 

this works fine. since have lot of parameters, end using on different places, idea let dict global. , know, global variables not great, wanted ensure dict , members immutable.

is approach? how do it? have it?

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bonus answerable stuff :)

is code ok? (it first thing did julia, , coming c/c++ , python have tendencies things differently.) need check whether file open? reading of file "julia"-like? readall , use eachmatch. don't see "right way it" (like in python).

why not use immutabledict? it's defined in base not exported. use 1 follows:

julia> id = base.immutabledict("key1"=>1) base.immutabledict{string,int64} 1 entry:   "key1" => 1  julia> id["key1"] 1  julia> id["key1"] = 2 error: methoderror: no method matching setindex!(::base.immutabledict{string,int64}, ::int64, ::string)  in eval(::module, ::any) @ .\boot.jl:234  in macro expansion @ .\repl.jl:92 [inlined]  in (::base.repl.##1#2{base.repl.replbackend})() @ .\event.jl:46  julia> id2 = base.immutabledict(id,"key2"=>2) base.immutabledict{string,int64} 2 entries:   "key2" => 2   "key1" => 1  julia> id.value 1 

you may want define constructor takes in array of pairs (or keys , values) , uses algorithm define whole dict (that's way so, see note @ bottom).

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just added note, actual internal representation each dictionary contains 1 key-value pair, , dictionary. method walks through dictionaries checking if has right value. reason because arrays mutable: if did naive construction of immutable type mutable field, field still mutable , while id["key1"]=2 wouldn't work, id.keys[1]=2 would. go around not using mutable type holding values (thus holding single values) , holding immutable dict. if wanted make work directly on arrays, use immutablearrays.jl don't think you'd performance advantage because you'd still have loop through array when checking key...