70 lines
2.0 KiB
Prolog
70 lines
2.0 KiB
Prolog
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% For number_codes/2 we want to just fail if the codes do not represent an integer.
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% gprolog.html#number-atom%2F2
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% > 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)
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:- set_prolog_flag(syntax_error, fail).
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joy_lex([tok(Token)|Ls]) --> chars(Token), !, joy_lex(Ls).
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joy_lex([ lbracket|Ls]) --> "[", !, joy_lex(Ls).
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joy_lex([ rbracket|Ls]) --> "]", !, joy_lex(Ls).
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joy_lex(Ls) --> blank, !, joy_lex(Ls).
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joy_lex([]) --> [].
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% Then parse the tokens converting them to Prolog values and building up
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% the list structures (if any.)
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joy_parse([J|Js]) --> joy_term(J), !, joy_parse(Js).
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joy_parse([]) --> [].
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joy_term(list(J)) --> [lbracket], !, joy_parse(J), [rbracket].
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joy_term(Token) --> [tok(Codes)], {joy_token(Token, Codes)}.
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joy_token(int(I), Codes) :- write(Codes) ,number_codes(I, Codes), !.
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joy_token(bool(true), "true") :- !.
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joy_token(bool(false), "false") :- !.
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joy_token(symbol(S), Codes) :- atom_codes(S, Codes).
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text_to_expression(Text, Expression) :-
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phrase(joy_lex(Tokens), Text), !,
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phrase(joy_parse(Expression), Tokens).
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% Apologies for all the (green, I hope) cuts. The strength of the Joy
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% syntax is that it's uninteresting.
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chars([Ch|Rest]) --> char(Ch), chars(Rest).
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chars([Ch]) --> char(Ch).
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char(Ch) --> \+ blank, [Ch], { Ch \== 0'[, Ch \== 0'] }.
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blank --> [9].
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blank --> [10].
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blank --> [11].
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blank --> [12].
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blank --> [13].
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blank --> [32].
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blank --> [194, 133].
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blank --> [194, 160].
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blank --> [225, 154, 128].
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blank --> [226, 128, 128].
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blank --> [226, 128, 129].
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blank --> [226, 128, 130].
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blank --> [226, 128, 131].
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blank --> [226, 128, 132].
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blank --> [226, 128, 133].
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blank --> [226, 128, 134].
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blank --> [226, 128, 135].
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blank --> [226, 128, 136].
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blank --> [226, 128, 137].
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blank --> [226, 128, 138].
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blank --> [226, 128, 168].
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blank --> [226, 128, 169].
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blank --> [226, 128, 175].
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blank --> [226, 129, 159].
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blank --> [227, 128, 128].
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