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:- 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) :-
get_char(C),
readLine_tail(C,L).
readLine_tail('\n',[]) :- !.
readLine_tail(C,[C|X]) :-
get_char(C2),
readLine_tail(C2,X).
wordList(X) --> whitespace, wordList(X).
wordList([X]) --> word(X).
wordList([X]) --> word(X), whitespace.
wordList([X|Y]) --> word(X), whitespace, wordList(Y).
word(W) --> charList(X), {atom_chars(W,X)}.
charList([X|Xs]) --> char(X), charList(Xs).
charList([X]) --> char(X).
whitespace --> whsp, whitespace.
whitespace --> whsp.
whsp --> oneOf(_,[' ', '\r', '\n', '\t']).
char(X) --> noneOf(X,[' ', '\r', '\n', '\t']).
oneOf(X,L) --> [X], {member(X,L)}.
noneOf(X,L) --> [X], {not(member(X,L))}.
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