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var Mexp = require('./lexer.js');
Mexp.prototype.toPostfix = function () {
'use strict';
var post = [], elem, popped, prep, pre, ele;
var stack = [{ value: "(", type: 4, pre: 0 }];
var arr = this.value;
for (var i = 1; i < arr.length; i++) {
if (arr[i].type === 1 || arr[i].type === 3 || arr[i].type === 13) { //if token is number,constant,or n(which is also a special constant in our case)
if (arr[i].type === 1)
arr[i].value = Number(arr[i].value);
post.push(arr[i]);
}
else if (arr[i].type === 4) {
stack.push(arr[i]);
}
else if (arr[i].type === 5) {
while ((popped = stack.pop()).type !== 4) {
post.push(popped);
}
}
else if (arr[i].type === 11) {
while ((popped = stack.pop()).type !== 4) {
post.push(popped);
}
stack.push(popped);
}
else {
elem = arr[i];
pre = elem.pre;
ele = stack[stack.length - 1];
prep = ele.pre;
var flag = ele.value == 'Math.pow' && elem.value == 'Math.pow';
if (pre > prep) stack.push(elem);
else {
while (prep >= pre && !flag || flag && pre < prep) {
popped = stack.pop();
ele = stack[stack.length - 1];
post.push(popped);
prep = ele.pre;
flag = elem.value == 'Math.pow' && ele.value == 'Math.pow';
}
stack.push(elem);
}
}
}
return new Mexp(post);
};
module.exports = Mexp;
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