//This BNF takes into consideration operator precedence:
// expression ::= <relexpr> (('&' | '|') <relexpr>)*
// relexpr ::= <addexpr> (('<' | '<=' | '>' | '>=' | '=' | '!=') <addexpr>)*
// addexpr ::= <mulexpr> (('+' | '-') <mulexpr>)*
// mulexpr ::= <term> (('*' | '/' | '%') <term>)*
// term is defined as before, see ParseTerm; thanks to that definition,
// unary operators have the highest precedence, as desired.
private void ParseExpression()
{
//After this method completes, the code generator should have
//available to it the result of the expression's evaluation (e.g.
//on the stack or in a predefined register).
ParseRelationalExpression();
while (IsNextTokenLogicalOp())
{
Token logicalOp = NextToken();
ParseRelationalExpression();
switch (logicalOp.Value)
{
case "&":
_codeGenerator.And();
break;
case "|":
_codeGenerator.Or();
break;
default:
ThrowCompilationException("Unexpected logical operator " + logicalOp.Value);
break;
}
}
}
