kattio.pl

% Prolog predicates for tokenized reading from stdin.
%
% Provides the following predicates:
% read_string(S): reads a string token
% read_int(I): reads an integer token
% read_atom(A): reads an atom
%
% For all three predicates, the result is unified with end_of_file
% if the end of the input stream was reached.
%

:- module(kattio, [read_string/1, read_int/1, read_atom/1]).

read_string(S) :-
	read_token_codes(S).

read_int(I) :-
	read_token_codes(Codes), 
	(Codes == end_of_file -> I = Codes ; number_codes(I, Codes)).

read_atom(A) :-
	read_token_codes(Codes),
	(Codes == end_of_file -> A = Codes ; atom_codes(A, Codes)).


% Internal predicate for getting the next token

read_token_codes(end_of_file) :-
	peek_code(end_of_file),	!.

read_token_codes(Codes) :-
	peek_code(C),
	\+ code_type(C, space), !,
	read_token_codes_helper(Codes).

read_token_codes(T) :-
	get_char(_), !,
	read_token_codes(T).


read_token_codes_helper([C0|C]) :-
	peek_code(C0),
	\+ code_type(C0, space), !,
	get_code(C0),
	read_token_codes_helper(C).

read_token_codes_helper([]).