:- module(read, [prompt/1, readList/1]).


% functions for obtaining a line of input text and parsing
% it into a list of words

% prompt provides the user with a '>' prompt as well
% readList merely obtains and parses the input


prompt(L) :-
    write('> '),
    readList(L).


readList(L) :-
    readLine(X),
    wordList(L,X,[]), !.


readLine(L) :-
    get0(C),
    buildLine(C,L).


buildLine(10,[]) :- !.
buildLine(C,[C|X]) :-
    get0(C2),
    buildLine(C2,X).


wordList([X|Y]) --> word(X), whitespace, wordList(Y).
wordList([X]) --> whitespace, wordList(X).
wordList([X]) --> word(X).
wordList([X]) --> word(X), whitespace.


word(W) --> charList(X), {name(W,X)}.


charList([X|Y]) --> char(X), charList(Y).
charList([X]) --> char(X).


char(X) --> [X], {X>=33}.


whitespace --> whsp, whitespace.
whitespace --> whsp.


whsp --> [X], {X<33}.