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104 lines
3.4 KiB
Mathematica
104 lines
3.4 KiB
Mathematica
%---------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%---------------------------------------------------------------------------%
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% Copyright (C) 2006-2007 The University of Melbourne.
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% Copyright (C) 2014-2015, 2018 The Mercury team.
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% This file is distributed under the terms specified in COPYING.LIB.
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%---------------------------------------------------------------------------%
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%
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% File: string.builder.m.
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% Main author: maclarty.
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%
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% This module implements a string builder stream. It can be used
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% to build up a string using string or character writers.
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%
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% To build up a string using this module, you first construct an initial
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% string builder state by calling the init function. You can then use
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% any instances of stream.writer that write strings or characters to update the
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% string builder state, using string.builder.handle as the stream argument.
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% Once you've finished writing to the string builder you can get the final
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% string by calling string.builder.to_string/1.
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%
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% For example:
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%
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% State0 = string.builder.init,
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% stream.string_writer.put_int(string.builder.handle, 5, State0, State),
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% Str = string.builder.to_string(State), % Str = "5".
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%
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%---------------------------------------------------------------------------%
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:- module string.builder.
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:- interface.
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:- import_module char.
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:- import_module stream.
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%---------------------------------------------------------------------------%
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:- type handle
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---> handle.
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:- type state.
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:- func init = (string.builder.state::uo) is det.
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:- instance stream.stream(string.builder.handle, string.builder.state).
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:- instance stream.output(string.builder.handle, string.builder.state).
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:- instance stream.writer(string.builder.handle, string, string.builder.state).
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:- instance stream.writer(string.builder.handle, char, string.builder.state).
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:- func to_string(string.builder.state::di) = (string::uo) is det.
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%---------------------------------------------------------------------------%
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%---------------------------------------------------------------------------%
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:- implementation.
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:- import_module list.
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:- type state
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---> state(list(string)).
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% A reversed list of the strings that, when unreversed
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% and appended together, yields the string we have built.
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init = state([]).
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:- instance stream.stream(string.builder.handle, string.builder.state)
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where [
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name(_, "<<string builder stream>>", !State)
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].
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:- instance stream.output(string.builder.handle, string.builder.state)
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where [
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flush(_, !State)
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].
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:- instance stream.writer(string.builder.handle, string, string.builder.state)
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where [
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( put(_, String, !State) :-
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!.State = state(StringList0),
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copy(String, UniqueString),
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StringList = [UniqueString | StringList0],
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!:State = state(StringList)
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)
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].
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:- instance stream.writer(string.builder.handle, char, string.builder.state)
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where [
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( put(_, Char, !State) :-
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!.State = state(StringList0),
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StringList = [string.from_char(Char) | StringList0],
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!:State = state(StringList)
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)
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].
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to_string(State) = String :-
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State = state(StringList),
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String = string.append_list(list.reverse(StringList)).
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%---------------------------------------------------------------------------%
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:- end_module string.builder.
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%---------------------------------------------------------------------------%
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