small erlang question.

Vladimir Sekissov <>
Fri Jan 16 00:05:38 CET 2004


Good day,

Yet another variant without functions:

Result =
  catch
    begin
      (0 == string:str(Text,Str1)) andalso (throw(Ret1)),
      (0 == string:str(Text,Str2)) andalso (throw(Ret2)),
      (0 == string:str(Text,Str3)) andalso (throw(Ret3)),
      none
    end,
...
or if you can change string:str/2 to return true|false

Result =
  catch
    begin
      string:str(Text,Str1) andalso (throw(Ret1)),
      string:str(Text,Str2) andalso (throw(Ret2)),
      string:str(Text,Str3) andalso (throw(Ret3)),
      none
    end,
...

Best Regards,
Vladimir Sekissov

peter> But better is:
peter> 
peter> case my_str(Text,[Str1,Str2,Str3]) of
peter>    1 -> do_1();
peter>    2 -> do_2();
peter>    3 -> do_3();
peter>    none -> ok
peter> end
peter> 
peter> where:
peter> 
peter> my_str(Text,L) -> my_str(Text,L,1).
peter> my_str(Text,[],N) -> none;
peter> my_str(Text,[Str|T],N) ->
peter>    case string:str(Text,Str) of
peter>      0 -> my_str(Text,T,N+1);
peter>      _ -> N
peter>    end.
peter> 
peter> But that was maybe about what you did yourself...
peter> 
peter> > case string:str(Text,Str1) of
peter> >    N when N /=0 -> do_a();
peter> >    _ ->
peter> >      case string:str(Text,Str2) of
peter> >         N2 when N2 /= 0 -> do_b();
peter> >         _ -> ....
peter> >      end
peter> > end
peter> >
peter> > OR:
peter> >
peter> > case string:str(Text,Str1) of
peter> >    0 ->
peter> >      case string:str(Text,Str2) of
peter> >         0 -> do_c();
peter> >         _ -> do_b();
peter> >      end;
peter> >    _ ->
peter> >      do_a()
peter> > end
peter> >
peter> > Are two obvious variants.
peter> >
peter> >> if (string:str(Text,String)  /= 0) -> ...;
peter> >>    (string:str(Text,String2) /= 0) ->...
peter> >> end
peter> >>
peter> >> but string:str is not accepted in a condition.
peter> >>
peter> >> I wrote a small function witch takes Text and a list of {Return_value,
peter> >> String} which tries each string and return Return_value if it matches:
peter> >>
peter> >> find_strings(_, []) -> false;
peter> >>
peter> >> find_strings(Texte,[{Retour,Chaine}|Liste])  ->
peter> >>         T1 = string:str(Texte, Chaine),
peter> >>         case T1 of
peter> >>                 0       -> find_strings(Texte,[Liste]);
peter> >>                 _Else   -> Retour
peter> >>         end
peter> >>         .
peter> >>
peter> >> but I wanted to know if there was not an other elegant solution that
peter> >> does not require a function.
peter> >>
peter> >> Regards.
peter> >>
peter> >> Raphaël.
peter> 
peter> 
peter> 



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