private Expression Unary()
{
if (look.Tag == '-')
{
Move();
return(new NegateExpression(Unary()));
}
if (look.Tag == '!')
{
Move();
return(new NotExpression(Unary()));
}
if (look.Tag == Tags.INCR)
{
Move();
Move();
return(UnaryArithmeticExpression.CreatePreIncrement(VariableUseExpression()));
}
if (look.Tag == Tags.DECR)
{
Move();
Move();
return(UnaryArithmeticExpression.CreatePreDecrement(VariableUseExpression()));
}
return(Factor());
}
private Expression Factor()
{
Expression expr = null;
switch (look.Tag)
{
case '(':
Move();
expr = Bool();
Match(')');
return(expr);
case Tags.NUMBER:
IntegerToken token = (IntegerToken)look;
expr = new IntConstantExpression(token.Value);
Move();
return(expr);
case Tags.REAL:
RealToken realToken = (RealToken)look;
expr = new FloatConstantExpression(realToken.Value);
Move();
return(expr);
case Tags.TRUE:
Move();
return(BoolConstantExpression.True);;
case Tags.FALSE:
Move();
return(BoolConstantExpression.False);
case Tags.ID:
Move();
if (look.Tag == '(')
{
return(FuncCallExpression());
}
else
{
VariableUseExpression varUseExpr = VariableUseExpression();
if (look.Tag == Tags.INCR)
{
Expression incrExpr = UnaryArithmeticExpression.CreatePostIncrement(varUseExpr);
Move();
return(incrExpr);
}
if (look.Tag == Tags.DECR)
{
Expression decrExpr = UnaryArithmeticExpression.CreatePostDecrement(varUseExpr);
Move();
return(decrExpr);
}
if (look.Tag == '=')
{
Move();
return(new VariableAssignExpression(varUseExpr, Bool()));
}
return(varUseExpr);
}
}
Error("Syntax error");
return(null);
}
