Fixes Basics.truncate for values larger than 32 bit ints

[Grannath]

The current native JavaScript implementation uses the n | 0 bit-wise operation to truncate the value. This is restricted by the definition of bit-wise operations. They are defined to operate on 32 bit signed integers.

In general, JavaScript allows 64 bit floating point numbers. With these, integers can be represented up to 2^53 - 1 aka Number.MAX_SAFE_INTEGER. By using a bit-wise operation, the usable range of Int in Elm is restricted artificially.

The implementation is replaced here with Math.ceil and Math.floor depending on the sign. Testing in a REPL now successfully evaluates e.g. truncate <| 2.45 * (2 ^ 33), which would have been impossible before.

Such a restriction is a) unnecessary and b) unexpected. I highly suggest removing it.

[process-bot]

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[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[witoldsz]

@evancz could you consider merging it "as is"? Today I had a nasty bug because of the return n | 0 implementation of truncate (the doc says nothing about cutting the number to 32 bits). The #721 umbrella is a nice idea, but this single bug could be fixed just now, what would you say?

[witoldsz]

@evancz could you consider merging it "as is"? Today I had a nasty bug because of the return n | 0 implementation of truncate (the doc says nothing about cutting the number to 32 bits). The #721 umbrella is a nice idea, but this single bug could be fixed just now, what would you say?

[harfangk]

I ran into this issue myself today. I hope this would get merged soon!
By the way, there's also Math.trunc() function in ES5, which corresponds to this function, but of course it's supported on relatively newer browsers.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/trunc

[harfangk]

I ran into this issue myself today. I hope this would get merged soon!
By the way, there's also Math.trunc() function in ES5, which corresponds to this function, but of course it's supported on relatively newer browsers.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/trunc