Implement BigNumber support for random

[ellis]

In mathjs v3.6.0, random() crashes when passed a BigNumber. The documentation seems to indicate that it should basically work:

Important: BigNumber is not supported by the following functions: gcd, lcm, xgcd, arg, random, atan2. These functions will downgrade BigNumber to Number, and return a Number.

But when I enter the following (as a minimalist example) at the node prompt:

var math = require('mathjs')
math.random(math.bignumber(1))

it produces the following error message:

TypeError: Invalid argument in function random
    at Object.randFunctions.random (./node_modules/mathjs/lib/function/probability/distribution.js:78:19)
    at repl:1:6
    at REPLServer.defaultEval (repl.js:262:27)
    at bound (domain.js:287:14)
    at REPLServer.runBound [as eval] (domain.js:300:12)
    at REPLServer.<anonymous> (repl.js:431:12)
    at emitOne (events.js:82:20)
    at REPLServer.emit (events.js:169:7)
    at REPLServer.Interface._onLine (readline.js:212:10)
    at REPLServer.Interface._line (readline.js:551:8)

The exception gets thrown here:

          if ((min !== undefined && !isNumber(min)) || (max !== undefined && !isNumber(max))) {
            throw new TypeError('Invalid argument in function random');
          }

I guess isNumber returns false for BigNumbers...? Or a coercion would need to take place before this check?

[josdejong]

Thanks for reporting, random(bignumber(2)) should indeed return a number instead of throw an error.

I see we have to update this section in the documentation, since for example gcd and lcm already support BigNumbers.

[josdejong]

Sorry, I remember now that we downgrade nowhere BigNumbers to numbers anymore, that was the behavior in mathjs v2. That means that random should indeed return an error as long as it doesn't support BigNumbers. I've updated the docs accordingly.

Let's just focus on implementing BigNumber support for random, that will solve all related issues.

[josdejong]

Oops closed the issue accidentally