恶狼传说[erlang字符串模拟php]

看着Erlang字符串操作不尽如人意，何不试着模拟实现php的字符串一些基本的操作？

最近又有点时间玩Erlang了，顺手先写下两个，有空再完善。

-module(mystring).
-export([strpos/2
    ,substr/2
    ,substr/3
    ,trim/1
    ,replace/3
    ,replace/4
    ,strstr/2
    ,strbef/2
    ,parse_str/1
    ,addslashes/1]).

%Function->[strpos]
%Get first location of character/string
%did not use any algorithm like kmp or sunday(should be improved later)
strpos(S,C) -> strpos(S,C,0).
strpos([H|T],[CH|CT],SS) -> 
        case CH == H of
                true    -> find([H|T],[CH|CT],[CH|CT],SS);
                false   -> strpos(T,[CH|CT],SS+1)
        end;
strpos([],_,_) -> -1. 
find([TH|TT],[FH|FT],C,TF) -> 
       case TH == FH of
               true  -> find(TT,FT,C,TF);
               false -> strpos(TT,C,TF+1)
       end;
find([],[],_,TF) -> TF;
find([],_,_,_)   -> -1;                                                                                                       
find(_,[],_,TF)  -> TF.

%Function->[substr]
%Get part of stirng,different from string:sub_string
substr(S,P)    -> ssubstr(S,P,0).
ssubstr([SH|ST],P,L) ->
    case L == P of
        true     -> [SH|ST];
        false    -> ssubstr(ST,P,L+1)
    end;
ssubstr([],_,_) -> [].

substr(S,P,E)    -> substr(S,P,E,0,[]).
substr([SH|ST],P,E,L,C)    ->
    if 
    E == 0        -> [];
        L == P             -> substr(ST,P,E,L+1,[SH|C]);
        L == E+P           -> lists:reverse(C);
        C == []            -> substr(ST,P,E,L+1,C);
        true               -> substr(ST,P,E,L+1,[SH|C])  
    end;
substr([],_,_,_,C) -> lists:reverse(C).

%Function->[trim]
%Strip space at beginning or end of string. 
%trim(S) -> lists:reverse(ltrim(lists:reverse(ltrim(S)))).
%ltrim([H|T]) ->
%    case [H] == " " of
%        true -> ltrim(T); 
%        false -> [H|T] 
%    end.
trim(S) -> string:strip(S,both,32).

%Function->[replace]
%Replace all/specific occurrences of `T` whith `R`
replace(S,T,R)      -> replace(S,T,R,all).
replace(S,T,R,C) -> 
    L = string:len(T),
    P = strpos(S,T),
    replace(S,T,R,P,L,C).
replace(S,T,R,P,L,C) ->
    NS = substr(S,0,P) ++ R,
    NP = substr(S,P+L), 
    if
        %We don't found the sub string
        P == -1   ->    S;     
        %Wanna replace all?    
        C == all  ->    NS ++ replace(NP,T,R);
        C == 0    ->    S;
        %Do specific times replacement.
        true      ->    NS ++ replace(NP,T,R,C-1)
    end.

%Function->[strstr]
%Get subsequent charaters with the first occurence charater/string
strstr(S,T) -> N = strpos(S,T),substr(S,N).
strbef(S,T) -> N = strpos(S,T),substr(S,0,N).

%Function->[parse_str]
%Parse query sting in url
parse_str(S)     ->  parse_str2(string:tokens(S,"&")).
%%%%ugly implement below.
%    FA         = strbef([T|H],"&"),
%    FS         = string:tokens(FA,"="),
%    SQ          = strstr([T|H],"&"),
%    case SQ == [] of
%        true     -> [FS];
%        false    -> [FS|parse_str(substr(SQ,1))]
%    end;
%parse_str([])        -> [].
%%%ugly implement end.
parse_str2([H|T]) -> [string:tokens(H,"=")|parse_str2(T)];
parse_str2([])      -> [].

 

运行结果。