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@@ -122,5 +122,156 @@ const ZhCalc = (function () {
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return value ? new Decimal(value).toDecimalPlaces(decimal).toNumber() : null;
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}
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- return {add, sub, mul, div, round, isNonZero: zhBaseCalc.isNonZero}
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+ const ExprCalc = {
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+ /**
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+ * 判断value是否是四则运算符
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+ * @param {String} value - 判断字符串
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+ * @return {Boolean}
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+ */
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+ isOperator(value) {
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+ const operatorString = "+-*/()";
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+ return operatorString.indexOf(value) > -1;
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+ },
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+ /**
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+ * Rpn解析栈
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+ * @param exp
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+ * @returns {Array}
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+ */
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+ parse2Rpn(exp) {
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+ const getPriority = function (value){
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+ switch(value){
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+ case '+':
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+ case '-':
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+ return 1;
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+ case '*':
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+ case '/':
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+ return 2;
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+ default:
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+ return 0;
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+ }
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+ };
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+ const priority = function (o1, o2){
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+ return getPriority(o1) <= getPriority(o2);
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+ };
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+
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+ const inputStack = [];
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+ const outputStack = [];
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+ const outputQueue = [];
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+
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+ for (let i = 0, len = exp.length; i < len; i++) {
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+ const cur = exp[i];
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+ if (cur !== ' ' ) {
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+ inputStack.push(cur);
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+ }
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+ }
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+ let num = '', isNumPre = false, isOperatorPre = false;
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+ while(inputStack.length > 0){
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+ const cur = inputStack.shift();
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+ if (this.isOperator(cur) && !(cur === '-' && !isNumPre)) {
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+ if (isNumPre) {
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+ outputQueue.push(parseFloat(num));
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+ num = '';
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+ }
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+ if (cur === '(') {
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+ outputStack.push(cur);
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+ } else if (cur === ')') {
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+ let po = outputStack.pop();
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+ while (po !== '(' && outputStack.length > 0) {
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+ outputQueue.push(po);
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+ po = outputStack.pop();
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+ }
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+ if (po !== '(') {
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+ throw "error: unmatched ()";
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+ }
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+ } else {
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+ while(priority(cur, outputStack[outputStack.length - 1]) && outputStack.length > 0){
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+ outputQueue.push(outputStack.pop());
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+ }
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+ outputStack.push(cur);
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+ }
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+ isNumPre = false;
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+ isOperatorPre = true;
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+ } else {
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+ num = num + cur;
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+ isNumPre = true;
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+ isOperatorPre = false;
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+ if (inputStack.length === 0) {
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+ outputQueue.push(parseFloat(num));
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+ }
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+ }
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+ }
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+ if (outputStack.length > 0) {
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+ if (outputStack[outputStack.length - 1] === ')' || outputStack[outputStack.length - 1] === '(') {
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+ throw "error: unmatched ()";
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+ }
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+ while (outputStack.length > 0) {
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+ outputQueue.push(outputStack.pop());
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+ }
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+ }
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+ return outputQueue;
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+ },
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+ /**
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+ * 计算Rpn解析栈
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+ * @param rpnQueue
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+ * @returns {*}
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+ */
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+ evalRpn(rpnQueue) {
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+ const getResult = function (num1, num2, opera) {
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+ switch (opera) {
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+ case '+':
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+ return add(num1, num1);
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+ case '-':
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+ return sub(num1, num2);
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+ case '*':
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+ return mul(num1, num2, 10);
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+ case '/':
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+ return div(num1, num2, 10);
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+ default:
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+ throw '参数错误';
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+ }
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+ };
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+ const outputStack = [];
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+ while(rpnQueue.length > 0){
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+ const cur = rpnQueue.shift();
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+
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+ if (!this.isOperator(cur)) {
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+ outputStack.push(cur);
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+ } else {
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+ if (outputStack.length < 2) {
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+ throw "unvalid stack length";
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+ }
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+ const sec = outputStack.pop();
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+ const fir = outputStack.pop();
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+
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+ outputStack.push(getResult(fir, sec, cur));
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+ }
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+ }
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+
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+ if (outputStack.length !== 1) {
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+ throw "unvalid expression";
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+ } else {
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+ return outputStack[0];
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+ }
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+ },
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+ /**
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+ * 解析四则运算字符串并计算
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+ * @param {String} expr
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+ * @returns
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+ */
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+ calcExprStrRpn(expr) {
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+ try {
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+ if (!isNaN(Number(expr))) {
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+ return Number(expr);
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+ } else {
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+ const rpnArr = this.parse2Rpn(expr);
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+ const result = this.evalRpn(rpnArr);
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+ return result === Infinity ? null : result;
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+ }
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+ } catch (err) {
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+ return null;
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+ }
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+ },
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+ };
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+
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+ return {add, sub, mul, div, round, isNonZero: zhBaseCalc.isNonZero, calcExpr: ExprCalc}
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})();
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