d_instruction.cpp

后辍表达式的计算

#include "d_instruction.h"

instruction::instruction()
{
}

instruction::instruction(char c)
{ 
	command=c;
	switch(c){
		case '+':
		case '-':
			inPriority=1;outPriority=1;break;
		case '*':
		case '/':
			inPriority=2;outPriority=2;break;
		case '(':
			inPriority=3;outPriority=-1;break;
		case ')':
			inPriority=0;outPriority=0;break;
	}
}

char instruction::getCommand() const
{ return command;
}

bool operator>=(const instruction& left,const instruction& right)
{ return left.outPriority>=right.inPriority;
}