JavaScript pi

Returns an approximation of pi

function pi () {
    // Returns an approximation of pi  
    // 
    // version: 1109.2015
    // discuss at: http://phpjs.org/functions/pi    // +   original by: Onno Marsman
    // +   improved by: dude
    // *     example 1: pi(8723321.4);
    // *     returns 1: 3.141592653589793
    return 3.141592653589793; // Math.PI}

external links: original PHP docs | raw js source

Examples

Running

1	pi(8723321.4);

Should return

1	3.141592653589793

Dependencies

No dependencies, you can use this function standalone.

Open syntax issues

php.js uses JsLint to help us keep our code consistent and prevent some common bugs.

Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.

Authors

Thanks to the following developers, you get to have pi goodness in JavaScript.

Onno Marsman ( original )
dude ( improved )

Comments

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Use:

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By submitting code here you are allowing us to use it in php.js hence dual licensing it under the MIT and GPL licenses

Brett Zamir
25 Jul '11

@dude: OK!!!! :) (I also applied in Git to some other functions using PI or LN10.)

dude
30 Jun '11

just go with "return 3.141592653589793" BECAUSE IT NEVER CHANGES!!!!

Onno Marsman
15 Oct '08

My opinions:

1. We don't want to actually recreate PHP. We want to make PHP functions available for javascript, so a function that returns Pi, should return the javascript representation of Pi. The same goes for sqrt(2).

2. I doubt that an increase in precision will bother anybody, or that a decrease will help anybody.

3. There is a more obvious type representation difference between PHP and javascript that is bothering a lot of people: associative arrays. In JS we need objects to do this. I would like to make all array functions in a way they can handle these objects next to the normal arrays, but of course we'll never make a new Array object which handles associative arrays as well. And that's basically what you're asking here: to create a new Number type, which behaves differently than the JS native one.

Could we and would we want to change the outcome of something like 1+pow(10, -15) ? I think not. (I haven't tested this for differences but you'll get the idea)

Philip Peterson
14 Oct '08

I guess similarly, shouldn't all numbers (e.g. square roots) be truncated to 14 digits?

Philip Peterson
14 Oct '08

Since PHP defaults to float 14, shouldn't we use the PHP-standard value of pi, 3.1415926535898 ?

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