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[poincare] Simpler precedence comparison in parser

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This commit is contained in:
Ruben Dashyan
2018-10-03 13:54:21 +02:00
committed by Émilie Feral
parent f5cbd56ac0
commit 20a1e048de
1 changed files with 2 additions and 16 deletions
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18
poincare/src/parsing/parser.cpp
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@@ -50,32 +50,18 @@ static inline bool tokenTypesCanBeImplicitlyMultiplied(Token::Type t1, Token::Ty
//TODO if (t1 == Token::Type::Identifier && t2 == Token::Type::LeftParenthesis) t1 should be parsed as a function
}
static inline bool comparePrecedence(Token::Type nextTokenType, Token::Type stoppingType) {
// if (stoppingType == EndOfStream) return nextTokenType > EndOfStream
// if (stoppingType == RightParenthesis) return nextTokenType > RightParenthesis
// if (stoppingType == Plus) return nextTokenType > Plus
// if (stoppingType == Times) return nextTokenType > Times
// if (stoppingType == Power) return nextTokenType >= Power // >= makes the operator right-associative
// EndOfStream < RightParenthesis < Plus < Times < Power
return
(nextTokenType > stoppingType)
||
(nextTokenType == stoppingType && stoppingType == Token::Type::Power);
}
bool Parser::canPopToken(Token::Type stoppingType) {
if (tokenTypesCanBeImplicitlyMultiplied(m_currentToken.type(), m_nextToken.type())) {
m_currentToken = Token(Token::Type::Times);
return true;
}
if (comparePrecedence(m_nextToken.type(), stoppingType)) {
if (m_nextToken.type() > stoppingType) {
popToken();
return true;
}
return false;
}
/* Specific TokenParsers */
Expression Parser::parseNumber(Expression leftHandSide) {
@@ -108,7 +94,7 @@ Expression Parser::parseMinus(Expression leftHandSide) {
Expression Parser::parsePower(Expression leftHandSide) {
assert(!leftHandSide.isUninitialized());
return Power(leftHandSide, parseUntil(Token::Type::Power)); // Power is right-associative
return Power(leftHandSide, parseUntil(Token::Type::Slash)); // Power is right-associative
}
Expression Parser::parseLeftParenthesis(Expression leftHandSide) {