thereadme/Equation.js
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Get around floating point precision of JavaScript fixes #5

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Fix `equation` not working on parentheses wrapped variables
Fixed `parseExpression` not working correctly on nested function operators
This commit is contained in:
Mahdi Dibaiee 2015-06-18 15:37:42 +04:30
parent 75969a4e1a
commit 2b3c06c413
6 changed files with 101 additions and 17 deletions
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36
dist/index.js vendored
View File

@ -72,7 +72,11 @@ var Equation = {
var stack = parseExpression(expression);
var variables = [];
stack.forEach(function (a) {
stack.forEach(function varCheck(a) {
if (Array.isArray(a)) {
return a.forEach(varCheck);
}
if (typeof a === 'string' && !_.isNumber(a) && !_operators2['default'][a] && a === a.toLowerCase()) {
// grouped variables like (y) need to have their parantheses removed
variables.push(_.removeSymbols(a));
@ -161,22 +165,30 @@ var parseExpression = function parseExpression(expression) {
}
// it's probably a function with a length more than one
if (!_.isNumber(cur) && !_operators2['default'][cur] && cur !== '.') {
if (!_.isNumber(cur) && !_operators2['default'][cur] && cur !== '.' && cur !== '(' && cur !== ')') {
record += cur;
} else if (record.length) {
stack.push(record, cur);
record = '';
} else if (_.isNumber(stack[stack.length - 1]) && (_.isNumber(cur) || cur === '.')) {
} else if (_.isNumber(stack[past]) && (_.isNumber(cur) || cur === '.')) {
stack[stack.length - 1] += cur;
stack[past] += cur;
// negation sign
} else if (stack[past] === '-') {
var beforeSign = stack[stack.length - 2];
var beforeSign = stack[past - 1];
// 2 / -5 is OK, pass
if (_operators2['default'][beforeSign]) {
stack[past] += cur;
// (2+1) - 5 becomes (2+1) + -5
} else if (beforeSign === ')') {
stack[past] = '+';
stack.push('-' + cur);
// 2 - 5 is also OK, pass
} else if (_.isNumber(beforeSign)) {
stack.push(cur);
} else {
@ -353,7 +365,7 @@ var evaluate = function evaluate(stack) {
var leftArguments = stack.slice(0, left),
rightArguments = stack.slice(left + 1);
return (_operators$op = _operators2['default'][op]).fn.apply(_operators$op, _toConsumableArray(leftArguments).concat(_toConsumableArray(rightArguments)));
return fixFloat((_operators$op = _operators2['default'][op]).fn.apply(_operators$op, _toConsumableArray(leftArguments).concat(_toConsumableArray(rightArguments))));
};
/**
@ -413,5 +425,17 @@ var replaceConstants = function replaceConstants(expression) {
});
};
/**
* Fixes JavaScript's floating point precisions - Issue #5
*
* @param {Number} number
* The number to fix
* @return {Number}
* Fixed number
*/
var fixFloat = function fixFloat(number) {
return +number.toFixed(15);
};
exports['default'] = Equation;
module.exports = exports['default'];

10
dist/operators.js vendored
View File

@ -109,6 +109,16 @@ exports['default'] = {
fn: Math.cot,
format: '10',
precedence: -1
},
round: {
fn: Math.round,
format: '10',
precedence: -1
},
floor: {
fn: Math.floor,
format: '10',
precedence: -1
}
};
module.exports = exports['default'];

11
dist/tests/solve.js vendored
View File

@ -32,6 +32,13 @@ describe('Basic math operators', function () {
it('should work for multi-digit numbers', function () {
_expect.expect(_M2['default'].solve('12+15')).to.equal(27);
});
it('should deal with floating precision of javascript - #5', function () {
_expect.expect(_M2['default'].solve('0.2 + 0.1')).to.equal(0.3);
_expect.expect(_M2['default'].solve('0.2 + 0.4')).to.equal(0.6);
_expect.expect(_M2['default'].solve('round(floor(1.23456789/0.2)) * 0.2')).to.equal(1.2);
_expect.expect(_M2['default'].solve('1.23456789 - (1.23456789 % 0.2)')).to.equal(1.2);
});
});
describe('Negative Numbers', function () {
@ -67,11 +74,11 @@ describe('Precedence', function () {
});
describe('Functions', function () {
it('should work for with parantheses', function () {
it('should work with parantheses', function () {
_expect.expect(_M2['default'].solve('lg(4) * 5')).to.equal(10);
});
it('should work for without parantheses', function () {
it('should work without parantheses', function () {
_expect.expect(_M2['default'].solve('lg4 * 5')).to.equal(10);
});

40
lib/index.js
View File

@ -49,7 +49,11 @@ let Equation = {
let stack = parseExpression(expression);
let variables = [];
stack.forEach(a => {
stack.forEach(function varCheck(a) {
if (Array.isArray(a)) {
return a.forEach(varCheck);
}
if (typeof a === 'string' && !_.isNumber(a) &&
!operators[a] && a === a.toLowerCase()) {
// grouped variables like (y) need to have their parantheses removed
@ -125,23 +129,32 @@ const parseExpression = expression => {
}
// it's probably a function with a length more than one
if (!_.isNumber(cur) && !operators[cur] && cur !== '.') {
if (!_.isNumber(cur) && !operators[cur] && cur !== '.' &&
cur !== '(' && cur !== ')') {
record += cur;
} else if (record.length) {
stack.push(record, cur);
record = '';
} else if (_.isNumber(stack[stack.length - 1]) &&
} else if (_.isNumber(stack[past]) &&
(_.isNumber(cur) || cur === '.')) {
stack[stack.length - 1] += cur;
} else if (stack[past] === '-') {
const beforeSign = stack[stack.length - 2];
stack[past] += cur;
// negation sign
} else if (stack[past] === '-') {
const beforeSign = stack[past - 1];
// 2 / -5 is OK, pass
if (operators[beforeSign]) {
stack[past] += cur;
// (2+1) - 5 becomes (2+1) + -5
} else if (beforeSign === ')') {
stack[past] = '+';
stack.push(`-${cur}`);
// 2 - 5 is also OK, pass
} else if (_.isNumber(beforeSign)) {
stack.push(cur);
} else {
@ -272,12 +285,13 @@ const evaluate = stack => {
if (!op) {
return stack[0];
}
const { left } = formatInfo(op);
let leftArguments = stack.slice(0, left),
rightArguments = stack.slice(left + 1);
return operators[op].fn(...leftArguments, ...rightArguments);
return fixFloat(operators[op].fn(...leftArguments, ...rightArguments));
};
/**
@ -315,4 +329,16 @@ const replaceConstants = expression => {
});
};
/**
* Fixes JavaScript's floating point precisions - Issue #5
*
* @param {Number} number
* The number to fix
* @return {Number}
* Fixed number
*/
const fixFloat = number => {
return +number.toFixed(15);
};
export default Equation;

10
lib/operators.js
View File

@ -88,5 +88,15 @@ export default {
fn: Math.cot,
format: '10',
precedence: -1
},
'round': {
fn: Math.round,
format: '10',
precedence: -1
},
'floor': {
fn: Math.floor,
format: '10',
precedence: -1
}
};

11
tests/solve.js
View File

@ -25,6 +25,13 @@ describe('Basic math operators', () => {
it('should work for multi-digit numbers', () => {
expect(M.solve('12+15')).to.equal(27);
});
it('should deal with floating precision of javascript - #5', () => {
expect(M.solve('0.2 + 0.1')).to.equal(0.3);
expect(M.solve('0.2 + 0.4')).to.equal(0.6);
expect(M.solve('round(floor(1.23456789/0.2)) * 0.2')).to.equal(1.2);
expect(M.solve('1.23456789 - (1.23456789 % 0.2)')).to.equal(1.2);
});
});
describe('Negative Numbers', () => {
@ -60,11 +67,11 @@ describe('Precedence', () => {
});
describe('Functions', () => {
it('should work for with parantheses', () => {
it('should work with parantheses', () => {
expect(M.solve('lg(4) * 5')).to.equal(10);
});
it('should work for without parantheses', () => {
it('should work without parantheses', () => {
expect(M.solve('lg4 * 5')).to.equal(10);
});