为调车场算法处理一元减号 [英] handling unary minus for shunting-yard algorithm

问题描述

在将中缀表达式转换为后缀表达式时，是否有更好的方法来处理一元-？

Is there a better way to handle unary "-" in converting a infix expression to a postfix one?

显而易见的是在每个一元-之前加上前缀0。有人知道更好的实现吗？谢谢！

The obvious one would be prefix every unary "-" with a 0. Does anyone know better implementation? Thanks!

推荐答案

我几年前的方式是为我的后缀表达式发明了一个新的运算符。因此，当我在前缀中遇到一元减号时，我会将其转换为＃。所以我的 a + -b 的后缀变成了 ab＃+ 。

The way I did this years ago was invent a new operator for my postfix expression. So when I encountered a unary minus in the infix, I'd convert it to #. So my postfix for a + -b became ab#+.

当然，我的评估者必须知道＃仅弹出一个操作数。

And, of course, my evaluator had to know that # only popped one operand.

种类的大小取决于构建后缀表达式的方式。如果要显示它，则特殊的＃运算符可能会使人们感到困惑。但是，如果您只是在内部使用（我曾经使用过），那么它会很好用。

Kind of depends on how you're using the postfix expression once it's built. If you want to display it then your special # operator would probably confuse people. But if you're just using it internally (which I was), then it works great.

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