56 lines
1.3 KiB
JavaScript
56 lines
1.3 KiB
JavaScript
function evalArithmeticExp(s) {
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s = s.replace(/\s/g,'').replace(/^\+/,'');
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var rePara = /\([^\(\)]*\)/;
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var exp = s.match(rePara);
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while (exp = s.match(rePara)) {
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s = s.replace(exp[0], evalExp(exp[0]));
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}
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return evalExp(s);
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function evalExp(s) {
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s = s.replace(/[\(\)]/g,'');
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var reMD = /\d+\.?\d*\s*[\*\/]\s*[+-]?\d+\.?\d*/;
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var reM = /\*/;
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var reAS = /-?\d+\.?\d*\s*[\+-]\s*[+-]?\d+\.?\d*/;
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var reA = /\d\+/;
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var exp;
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while (exp = s.match(reMD)) {
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s = exp[0].match(reM)? s.replace(exp[0], multiply(exp[0])) : s.replace(exp[0], divide(exp[0]));
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}
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while (exp = s.match(reAS)) {
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s = exp[0].match(reA)? s.replace(exp[0], add(exp[0])) : s.replace(exp[0], subtract(exp[0]));
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}
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return '' + s;
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function multiply(s, b) {
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b = s.split('*');
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return b[0] * b[1];
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}
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function divide(s, b) {
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b = s.split('/');
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return b[0] / b[1];
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}
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function add(s, b) {
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s = s.replace(/^\+/,'').replace(/\++/,'+');
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b = s.split('+');
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return Number(b[0]) + Number(b[1]);
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}
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function subtract(s, b) {
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s = s.replace(/\+-|-\+/g,'-');
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if (s.match(/--/)) {
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return add(s.replace(/--/,'+'));
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}
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b = s.split('-');
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return b.length == 3? -1 * b[1] - b[2] : b[0] - b[1];
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}
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}
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}
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