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46 parser

%--------------------------------------------------%
% vim: ft=mercury ts=4 sw=4 et wm=0 tw=0
%--------------------------------------------------%
% Copyright (C) 1995-2001, 2003-2008, 2011-2012 The University of Melbourne.
% This file may only be copied under the terms of the GNU Library General
% Public License - see the file COPYING.LIB in the Mercury distribution.
%--------------------------------------------------%
%
% File: parser.m.
% Main author: fjh.
% Stability: high.
%
% This file exports the predicate read_term, which reads
% a term from the current input stream.
% The read_term_from_string predicates are the same as the
% read_term predicates, except that the term is read from
% a string rather than from the current input stream.
% The parse_token_list predicate is similar,
% but it takes a list of tokens rather than a string.
%
% The parser and lexer are intended to exactly follow ISO Prolog
% syntax, but there are some departures from that for three reasons:
%
%   (1) I wrote some of the code at home when the ISO Prolog draft
%       was at uni - so in some places I just guessed.
%   (2) In some places the lexer reports an error when it shouldn't.
%   (3) There are a couple of hacks to make it compatible with NU-Prolog
%       syntax.
%
% The parser is a relatively straight-forward top-down recursive descent
% parser, made somewhat complicated by the need to handle operator
% precedences.  It uses `lexer.get_token_list' to read a list of tokens.
% It uses the routines in module `ops' to look up operator precedences.
%
%--------------------------------------------------%
%--------------------------------------------------%

:- module parser.
:- interface.

:- import_module io.
:- import_module lexer.
:- import_module ops.
:- import_module term_io.

%--------------------------------------------------%

    % read_term(Result, !IO):
    % read_term(Stream, Result, !IO):
    %
    % Reads a Mercury term from the current input stream or from Stream.
    %
:- pred read_term(read_term(T)::out, io::di, io::uo) is det.
:- pred read_term(io.text_input_stream::in, read_term(T)::out,
    io::di, io::uo) is det.

    % read_term_with_op_table(Ops, Result, !IO):
    % read_term_with_op_table(Stream, Ops, Result, !IO):
    %
    % Reads a term from the current input stream or from Stream,
    % using the given op_table to interpret the operators.
    %
:- pred read_term_with_op_table(Ops::in,
    read_term(T)::out, io::di, io::uo) is det <= op_table(Ops).
:- pred read_term_with_op_table(io.text_input_stream::in, Ops::in,
    read_term(T)::out, io::di, io::uo) is det <= op_table(Ops).

    % read_term_filename(FileName, Result, !IO):
    % read_term_filename(Stream, FileName, Result, !IO):
    %
    % Reads a term from the current input stream or from Stream.
    % The string is the filename to use for the stream; this is used
    % in constructing the term.contexts in the read term.
    % This interface is used to support the `:- pragma source_file' directive.
    %
:- pred read_term_filename(string::in,
    read_term(T)::out, io::di, io::uo) is det.
:- pred read_term_filename(io.text_input_stream::in, string::in,
    read_term(T)::out, io::di, io::uo) is det.

    % read_term_filename_with_op_table(Ops, FileName, Result, !IO):
    % read_term_filename_with_op_table(Stream, Ops, FileName, Result, !IO):
    %
    % As above but using the given op_table.
    %
:- pred read_term_filename_with_op_table(Ops::in,
    string::in, read_term(T)::out, io::di, io::uo) is det <= op_table(Ops).
:- pred read_term_filename_with_op_table(io.text_input_stream::in, Ops::in,
    string::in, read_term(T)::out, io::di, io::uo) is det <= op_table(Ops).

%--------------------------------------------------%

    % The read_term_from_string predicates are the same as the read_term
    % predicates, except that the term is read from a string rather than from
    % the current input stream. The returned value `EndPos' is the position
    % one character past the end of the term read. The arguments `MaxOffset'
    % and `StartPos' in the six-argument version specify the length of the
    % string and the position within the string at which to start parsing.

    % read_term_from_string(FileName, String, EndPos, Term).
    %
:- pred read_term_from_string(string::in, string::in, posn::out,
    read_term(T)::out) is det.

    % read_term_from_string_with_op_table(Ops, FileName,
    %   String, EndPos, Term).
    %
:- pred read_term_from_string_with_op_table(Ops::in, string::in,
    string::in, posn::out, read_term(T)::out) is det <= op_table(Ops).

    % read_term_from_string(FileName, String, MaxOffset, StartPos,
    %   EndPos, Term).
    %
:- pred read_term_from_substring(string::in, string::in, int::in,
    posn::in, posn::out, read_term(T)::out) is det.

    % read_term_from_string_with_op_table(Ops, FileName, String,
    %   MaxOffset, StartPos, EndPos, Term).
    %
:- pred read_term_from_substring_with_op_table(Ops::in, string::in,
    string::in, int::in, posn::in, posn::out, read_term(T)::out) is det
    <= op_table(Ops).

%--------------------------------------------------%

    % parse_tokens(FileName, TokenList, Result):
    %
:- pred parse_tokens(string::in, token_list::in, read_term(T)::out) is det.

    % parse_tokens(FileName, TokenList, Result):
    %
:- pred parse_tokens_with_op_table(Ops::in, string::in, token_list::in,
    read_term(T)::out) is det <= op_table(Ops).

%--------------------------------------------------%
%--------------------------------------------------%


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