thereadme/Equation.js
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Add support for NumVariable expressions such as 2x fixes #6

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This commit is contained in:
Mahdi Dibaiee 2015-06-18 16:14:13 +04:30
parent 2b3c06c413
commit c6973847aa
5 changed files with 111 additions and 22 deletions
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4
README.md
View File

@ -18,8 +18,10 @@ console.log(Equation.solve('4 * lg(4) ^ 3')); // 32
// equation
let sphereArea = Equation.equation('4 * PI * r^2');
console.log(sphereArea(5)); // 314.1592653589793
let test = Equation.equation('2x + 6y');
console.log(test(4, 3)).to.equal(8 + 18);
```
You can also register your own operators and constants.

61
dist/index.js vendored
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@ -70,14 +70,14 @@ var Equation = {
*/
equation: function equation(expression) {
var stack = parseExpression(expression);
console.log(stack);
var variables = [];
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()) {
if (isVariable(a)) {
// grouped variables like (y) need to have their parantheses removed
variables.push(_.removeSymbols(a));
}
@ -88,15 +88,30 @@ var Equation = {
args[_key] = arguments[_key];
}
expression = expression.replace(/[a-z]*/g, function (a) {
stack.forEach(function varCheck(a, i, arr) {
if (Array.isArray(a)) {
return a.forEach(varCheck);
}
var index = variables.indexOf(a);
if (index > -1) {
return args[index] || 0;
// grouped variables like (y) need to have their parantheses removed
arr[i] = args[index];
}
return a;
});
return Equation.solve(expression);
stack = sortStack(stack);
stack = _.parseNumbers(stack);
stack = solveStack(stack);
// expression = expression.replace(/[a-z]*/g, a => {
// let index = variables.indexOf(a);
// if (index > -1) {
// return args[index] || 0;
// }
// return a;
// });
return stack;
};
},
@ -154,12 +169,15 @@ var MIN_PRECEDENCE = Math.min.apply(Math, _toConsumableArray(PRECEDENCES));
var parseExpression = function parseExpression(expression) {
var stream = new _ReadStream2['default'](expression),
stack = [],
record = '';
record = '',
cur = undefined,
past = undefined;
// Create an array of separated numbers & operators
while (stream.next()) {
var cur = stream.current(),
past = stack.length - 1;
cur = stream.current();
past = stack.length - 1;
if (cur === ' ') {
continue;
}
@ -169,8 +187,14 @@ var parseExpression = function parseExpression(expression) {
record += cur;
} else if (record.length) {
var beforeRecord = past - (record.length - 1);
if (isVariable(record) && _.isNumber(stack[beforeRecord])) {
stack.push('*');
}
stack.push(record, cur);
record = '';
// numbers and decimals
} else if (_.isNumber(stack[past]) && (_.isNumber(cur) || cur === '.')) {
stack[past] += cur;
@ -199,6 +223,10 @@ var parseExpression = function parseExpression(expression) {
}
}
if (record.length) {
var beforeRecord = past - (record.length - 1);
if (isVariable(record) && _.isNumber(stack[beforeRecord])) {
stack.push('*');
}
stack.push(record);
}
@ -437,5 +465,16 @@ var fixFloat = function fixFloat(number) {
return +number.toFixed(15);
};
exports['default'] = Equation;
module.exports = exports['default'];
/**
* Recognizes variables such as x, y, z
* @param {String} a
* The string to check for
* @return {Boolean}
* true if variable, else false
*/
var isVariable = function isVariable(a) {
return typeof a === 'string' && !_.isNumber(a) && !_operators2['default'][a] && a === a.toLowerCase();
};
exports.isVariable = isVariable;
exports['default'] = Equation;

5
dist/tests/equation.js vendored
View File

@ -30,6 +30,11 @@ describe('Equations', function () {
_expect.expect(equation).to['throw']();
});
it('should work with NumVariable expressions like 2x', function () {
var equation = _M2['default'].equation('2x + 6y');
_expect.expect(equation(4, 3)).to.equal(8 + 18);
});
it('Test case', function () {
var equation = _M2['default'].equation('2+x*(y+4)+z^2');
_expect.expect(equation(2, 4, 3)).to.equal(27);

58
lib/index.js
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@ -47,30 +47,44 @@ let Equation = {
*/
equation(expression) {
let stack = parseExpression(expression);
console.log(stack);
let variables = [];
stack.forEach(function varCheck(a) {
if (Array.isArray(a)) {
return a.forEach(varCheck);
}
if (typeof a === 'string' && !_.isNumber(a) &&
!operators[a] && a === a.toLowerCase()) {
if (isVariable(a)) {
// grouped variables like (y) need to have their parantheses removed
variables.push(_.removeSymbols(a));
}
});
return function(...args) {
expression = expression.replace(/[a-z]*/g, a => {
stack.forEach(function varCheck(a, i, arr) {
if (Array.isArray(a)) {
return a.forEach(varCheck);
}
let index = variables.indexOf(a);
if (index > -1) {
return args[index] || 0;
// grouped variables like (y) need to have their parantheses removed
arr[i] = args[index];
}
return a;
});
return Equation.solve(expression);
stack = sortStack(stack);
stack = _.parseNumbers(stack);
stack = solveStack(stack);
// expression = expression.replace(/[a-z]*/g, a => {
// let index = variables.indexOf(a);
// if (index > -1) {
// return args[index] || 0;
// }
// return a;
// });
return stack;
};
},
@ -118,12 +132,14 @@ const MIN_PRECEDENCE = Math.min(...PRECEDENCES);
const parseExpression = expression => {
let stream = new ReadStream(expression),
stack = [],
record = '';
record = '',
cur, past;
// Create an array of separated numbers & operators
while (stream.next()) {
const cur = stream.current(),
past = stack.length - 1;
cur = stream.current();
past = stack.length - 1;
if (cur === ' ') {
continue;
}
@ -134,8 +150,14 @@ const parseExpression = expression => {
record += cur;
} else if (record.length) {
let beforeRecord = past - (record.length - 1);
if (isVariable(record) && _.isNumber(stack[beforeRecord])) {
stack.push('*');
}
stack.push(record, cur);
record = '';
// numbers and decimals
} else if (_.isNumber(stack[past]) &&
(_.isNumber(cur) || cur === '.')) {
@ -165,6 +187,10 @@ const parseExpression = expression => {
}
}
if (record.length) {
let beforeRecord = past - (record.length - 1);
if (isVariable(record) && _.isNumber(stack[beforeRecord])) {
stack.push('*');
}
stack.push(record);
}
@ -341,4 +367,16 @@ const fixFloat = number => {
return +number.toFixed(15);
};
/**
* Recognizes variables such as x, y, z
* @param {String} a
* The string to check for
* @return {Boolean}
* true if variable, else false
*/
export const isVariable = a => {
return typeof a === 'string' && !_.isNumber(a) &&
!operators[a] && a === a.toLowerCase();
};
export default Equation;

5
tests/equation.js
View File

@ -23,6 +23,11 @@ describe('Equations', () => {
expect(equation).to.throw();
});
it('should work with NumVariable expressions like 2x', () => {
let equation = M.equation('2x + 6y');
expect(equation(4, 3)).to.equal(8 + 18);
});
it('Test case', () => {
let equation = M.equation('2+x*(y+4)+z^2');
expect(equation(2, 4, 3)).to.equal(27);