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Parse the tokens into a Joy expression.

This commit is contained in:
Simon Forman 2022-09-20 17:14:41 -07:00
parent c8f67f02f9
commit b49e7458c2
1 changed files with 21 additions and 20 deletions
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41
implementations/GNUProlog/parser.prolog
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@ -1,6 +1,12 @@
joy_lex([tok(Token)|Ls]) --> chars(TokenCodes), !, {atom_codes(Token, TokenCodes)}, joy_lex(Ls).
% For number_codes/2 we want to just fail if the codes do not represent an integer.
% gprolog.html#number-atom%2F2
% > Number is a variable, Atom (or Chars or Codes) cannot be parsed as a number and the value of the syntax_error Prolog flag is error (section 8.22.1)
:- set_prolog_flag(syntax_error, fail).
joy_lex([tok(Token)|Ls]) --> chars(Token), !, joy_lex(Ls).
joy_lex([ lbracket|Ls]) --> "[", !, joy_lex(Ls).
joy_lex([ rbracket|Ls]) --> "]", !, joy_lex(Ls).
@ -12,21 +18,20 @@ joy_lex([]) --> [].
% Then parse the tokens converting them to Prolog values and building up
% the list structures (if any.)
%joy_parse([J|Js]) --> joy_term(J), !, joy_parse(Js).
%joy_parse([]) --> [].
%
%joy_term(list(J)) --> [lbracket], !, joy_parse(J), [rbracket].
%joy_term(Token) --> [tok(Codes)], {joy_token(Token, Codes)}.
%
%joy_token(int(I), Codes) :- number(I, Codes, []), !. % See dcg/basics.
%joy_token(bool(true), `true`) :- !.
%joy_token(bool(false), `false`) :- !.
%joy_token(symbol(S), Codes) :- atom_codes(S, Codes).
%
%
%text_to_expression(Text, Expression) :-
% phrase(joy_lex(Tokens), Text), !,
% phrase(joy_parse(Expression), Tokens).
joy_parse([J|Js]) --> joy_term(J), !, joy_parse(Js).
joy_parse([]) --> [].
joy_term(list(J)) --> [lbracket], !, joy_parse(J), [rbracket].
joy_term(Token) --> [tok(Codes)], {joy_token(Token, Codes)}.
joy_token(int(I), Codes) :- write(Codes) ,number_codes(I, Codes), !.
joy_token(bool(true), "true") :- !.
joy_token(bool(false), "false") :- !.
joy_token(symbol(S), Codes) :- atom_codes(S, Codes).
text_to_expression(Text, Expression) :-
phrase(joy_lex(Tokens), Text), !,
phrase(joy_parse(Expression), Tokens).
% Apologies for all the (green, I hope) cuts. The strength of the Joy
% syntax is that it's uninteresting.
@ -62,7 +67,3 @@ blank --> [226, 128, 169].
blank --> [226, 128, 175].
blank --> [226, 129, 159].
blank --> [227, 128, 128].
do :- phrase(joy_lex(Tokens), "23[15]").