CODEWITHSUNDEEP
stringsplitprologswi-prologpunctuation
Sofia
Sofia

Reputation: 456

How to keep punctuation as a separate element in split_string in Prolog

I'm doing an assignment in Prolog (I'm a newbie) and I have a small problem. I know you can split a string to a list of elements in Prolog like this:

split_string("Hello, here I am!"," "," .!?-_'",Temp).

But this takes out the basic punctuation. It returns:

Temp = ['Hello','here','I','am'].

How can I change it in order to keep the punctuation like this:

Temp = ['Hello',',','here','I','am','!'].

Thank you in advance for your help!

Upvotes: 0

Views: 406

Answers (1)

pasaba por aqui
pasaba por aqui

Reputation: 3529

"split_string" is not standard but, in the implementation I know, you can not. From the ECLIPSe manual:

The string String is split at the separators, and any padding characters around the resulting sub-strings are removed. Neither the separators nor the padding characters occur in SubStrings.

http://www.cs.uni-potsdam.de/wv/lehre/Material/Prolog/Eclipse-Doc/bips/kernel/stratom/split_string-4.html

** Addendum **

We can play a few with string functions to recover the "list" separators:

split_with_delimiters(String,Delimiters,Ignore,Result) :-
   split_string(String,Delimiters,"",FirstSplit),
   split_with_delimiters_aux(Ignore,String,FirstSplit,Result).

split_with_delimiters_aux(_,"",_,[]) :- !.

split_with_delimiters_aux(Ignore,String,[""|Q],Result) :- !,
   split_with_delimiters_aux(Ignore,String,Q,Result).

split_with_delimiters_aux(Ignore,String,[H|Q],[H|Result]) :-
   string_concat( H, Rest, String ), !,
   split_with_delimiters_aux(Ignore,Rest,Q,Result).

split_with_delimiters_aux(Ignore,String,Split,Result) :- 
   sub_string( String, 0, 1, RestL, Delimiter ),
   sub_string( String, 1, RestL, _, Rest ),
   sub_string( Delimiter, _, _, _, Ignore ), !,
   split_with_delimiters_aux(Ignore,Rest,Split,Result).

split_with_delimiters_aux(Ignore,String,Split,[Delimiter|Result]) :-
   sub_string( String, 0, 1, RestL, Delimiter ),
   sub_string( String, 1, RestL, _, Rest ),
   split_with_delimiters_aux( Ignore,Rest, Split, Result ).

that provides following result:

?- split_with_delimiters("Hello, here I am!"," ,.!?-_'"," ",Res).
Res = ["Hello", ",", "here", "I", "am", "!"]

(things could be easier if we convert string to/from list at start/end)

Upvotes: 1

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