flex/as 版 eval 字符串 四则混合 运算
1.传入一个带四则运算的字符串。（如：var a:String = "2*(4-3.001)+3.5";）.
2.返回值为被解析后四则运算出来的结果值。
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package com.zzz { public class MathExpress { public function MathExpress() { } public static function MathExpressByStr(str:String):String{ str = "(" + str.replace(/[^\d.+-*\/()]+/g,"") + ")"; while (/\([^()]*\)/.test(str)){ str = str.replace(/\(([^()]*)\)/g,function(s, b){ while (/[*\/]/.test(b)){ b = b.replace(/([\d.]+)([*\/])([\d.]+)/g,function(c, m, l, n){ var i:Number = parseFloat(m); var j:Number = parseFloat(n); return l=="*" ? i*j : i/j; }) } while (/[+-]/.test(b)){ b = b.replace(/([\d.]+)([+-])([\d.]+)/g,function(c, m, l, n){ var i:Number = parseFloat(m); var j:Number = parseFloat(n); return l=="+" ? i+j : i-j; }) } return b; }) } return str; } } } ?3.得最后结果：7.498
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转至:http://blog.csdn.net/zzz_robinson/article/details/7239829
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private function evalString(infix:String):String{ var opArray:Array = new Array(); //栈底标记 opArray[0] = '@'; var op:Number = 1; var postfix:Array = new Array(); var post:Number = 0; //保存计算结果 var res:Number = 0; var i, j; var tempString:String = new String(); //计算两个数 function Caculate(opSign:String) { if (opSign == '+') { res = postfix[post-2]+postfix[post-1]; } else if (opSign == '-') { res = postfix[post-2]-postfix[post-1]; } else if (opSign == '*') { res = postfix[post-2]*postfix[post-1]; } else if (opSign == '/') { if (!postfix[post-1]) { trace("Expression Error!"); } else { res = postfix[post-2]/postfix[post-1]; } } postfix[post-1] = 0; postfix[post-2] = res; post--; } //扫描中缀表达式 for (i=0; i<infix.length; i++) { switch (infix.charAt(i)) { //左括号就直接入栈 case '(' : opArray[op] = infix.charAt(i); op++; break; //右括号则退栈计算，直到遇见一个左括号 case ')' : for (j=op-1; j>0; j--) { if (opArray[j] != '(') { Caculate(opArray[j]); opArray[j] = '#'; } else { opArray[j] = '#'; break; } } op = j; break; case '*' : case '/' : //如果栈顶的运算符为*或/，则先退栈，再入栈，否则直接入栈 if (opArray[op-1] == '*') { op--; Caculate(opArray[op]); opArray[op] = '#'; } else if (opArray[op-1] == '/') { op--; Caculate(opArray[op]); opArray[op] = '#'; } opArray[op] = infix.charAt(i); op++; break; case '+' : case '-' : //如果栈顶的运算符不是左括号也不是栈底，则先退栈计算，再入栈 if (opArray[op-1] != '(' && opArray[op-1] != '@') { op--; Caculate(opArray[op]); opArray[op] = '#'; } opArray[op] = infix.charAt(i); op++; break; default : //如果是数字字符或者小数点则转化为数字存入数组 //如果下一个字符是运算符则把当前数字存入数组 tempString += infix.charAt(i); var temp:String = new String(); temp = infix.charAt(i+1); if (temp != '.' && (temp>'9' || temp<'0')) { postfix[post] = parseFloat(tempString); post++; tempString = ""; } //trace(postfix); } } //扫描完成，全部退栈 for (j=op-1; j>0; j--) { if (opArray[j] != '@') { Caculate(opArray[j]); opArray[j] = '#'; } else { break; } } //返回结果 return postfix[0]; }?转至：http://blog.csdn.net/zzz_robinson/article/details/7311629
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