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// Copyright (C) 1994 The New York Group Theory Cooperative
// See magnus/doc/COPYRIGHT for the full notice.
// Contents: Definition of parser for presentations.
//
// Principal Author: Roger Needham
//
// Status: useable
//
// Revision History:
//
#ifndef _PRESENTATION_PARSER_H_
#define _PRESENTATION_PARSER_H_
#include "Set.h"
#include "WordParser.h"
#include "FreeGroup.h"
#include "FPGroup.h"
// The grammar for Word and FPGroup:
//
// Literals are delimited by ''.
// The symbols ., *, +, -, |, ?, [, ], (, and ) are part of regular expressions
// unless quoted.
//
// <whitespace> ::= ' ' | '\t' | '\n' | '#'.*'\n'
// <index> ::= 0 | [1-9]+[0-9]*
// <integer> ::= <index> | -<index>
// <generator> ::= [a-zA-Z]+<index>?
// <atom> ::= '1' | <generator> | '('<word>')' |
// '['<word>','<word>(','<word>)*']'
// <term> ::= <atom>('^'<atom>)* | <term>'^'<integer>
// <word> ::= <term>('*'<term>)* | <term>(<whitespace><term>)*
// <relator> ::= <word>('='<word>)?
// <generator list> ::= (<generator>(','<generator>)*)?
// <word list> ::= <word>(','<word list>)?
// <relator list> ::= <word>('='<word>)* |
// (<word>('='<word>)*(','<word>('='<word>)*)?)?
// <FPGroup> ::= '<'<generator list>('|' | ';' | ':')<relator list>'>' |
// '<'<generator list>'>'
//
// - whitespace may occur anywhere except within lexemes.
//
// Semantic conventions:
//
// - x^y is y^-1 x y.
// - ^ is left-associative, so a^t^2 is (a^t)^2.
// - [x,y] is x^-1 y^-1 x y.
// - [x1, x2, ..., xn] is left-normed: [[x1,x2], x3, ..., xn].
// - Given the print name of a generator, the print name of its inverse
// has each character changed to the opposite case.
// Thus aB2^-1 is the same as Ab2.
class PresentationParser : public WordParser {
public:
enum BraceType { SET, PAREN };
public:
PresentationParser(istream &istr) : WordParser(istr) { }
// Initialize the parser with the istream from which to read.
// Destructor supplied by compiler.
VectorOf<Chars> parseGeneratorList( Chars& );
// Read a generator list.
SetOf<Word> parseWordSet( const VectorOf<Chars>&, Chars& );
// Read a list of words in the given generator names.
// The list is terminated when a word is followed by any non-whitespace
// char other than ','.
VectorOf<Word> parseWordList( const VectorOf<Chars>&, Chars& );
// Read a list of words in the given generator names.
// The list is terminated when a word is followed by any non-whitespace
// char other than ','.
SetOf<Word> parseSetOfWords( const VectorOf<Chars>&, Chars& );
// Read a list of words in the given generator names delimited by '{', '}'.
VectorOf<Word> parseVectorOfWords( const VectorOf<Chars>&, Chars&,
BraceType brace = SET );
// Read a list of words in the given generator names delimited by '{', '}'
// or '(', ')'.
virtual Word parseRelator( const VectorOf<Chars>&, Chars& );
// Read a relator in the given generator names.
SetOf<Word> parseRelatorList( const VectorOf<Chars>&, Chars& );
// Read a list of words and relations in the given generator names.
// The list is terminated when anything (non-whitespace) other than
// a relator or ',' is encountered.
FreeGroupRep* parseFreeGroup( Chars& );
FPGroupRep* parseFPGroup( Chars& );
// Read a group presentation and return it as a new group rep object.
private:
bool getGeneratorRange( const Chars& , VectorOf<Chars>&, Chars& );
bool getRangeOf( const Chars& ,Chars&, int& );
};
#endif
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