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layout: default
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Function parser #
Create a `math.Parser` object that keeps a context of variables and their values, allowing the evaluation of expressions in that context.
Syntax #
```js
math.parser()
```
Parameters #
Parameter | Type | Description
--------- | ---- | -----------
Returns #
Type | Description
---- | -----------
Parser | Parser
Throws #
Type | Description
---- | -----------
Examples #
```js
const parser = new math.parser()
// evaluate expressions
const a = parser.evaluate('sqrt(3^2 + 4^2)') // 5
const b = parser.evaluate('sqrt(-4)') // 2i
const c = parser.evaluate('2 inch in cm') // 5.08 cm
const d = parser.evaluate('cos(45 deg)') // 0.7071067811865476
// define variables and functions
parser.evaluate('x = 7 / 2') // 3.5
parser.evaluate('x + 3') // 6.5
parser.evaluate('f(x, y) = x^y') // f(x, y)
parser.evaluate('f(2, 3)') // 8
// get and set variables and functions
const x = parser.get('x') // 3.5
const f = parser.get('f') // function
const g = f(3, 2) // 9
parser.set('h', 500)
const i = parser.evaluate('h / 2') // 250
parser.set('hello', function (name) {
return 'hello, ' + name + '!'
})
parser.evaluate('hello("user")') // "hello, user!"
// clear defined functions and variables
parser.clear()
```
See also #
[evaluate](evaluate.html),
[compile](compile.html),
[parse](parse.html)