Bug: Integer Precision on PC versus Mac

[blogscot]

While trying to solve an exercism.io problem, I encountered the following issue:

On Windows 10 PC, Elm 0.17.1:

> a = 2329871239
-1965096057 : number
> a = 2329871239.0
2329871239 : Float

While on Mac OS X, Elm 0.17.1

a = 2329871239
2329871239 : number
> a = 2329871239.0
2329871239 : Float

This problem was discussed on the Elm Slack Channel, where it was confirmed that this issue was present on an independent Windows 10 machine running the same Elm version.

[process-bot]

Thanks for the issue! 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.

[process-bot]

Thanks for the issue! 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.

[evancz]

This is due to the fact that Elm compiles to JS. Unless JS is different, or unless we compile to some other thing, I see no practical way to do anything about this. If there is some concrete proposal, we can talk about that in a new issue.

[evancz]

This is due to the fact that Elm compiles to JS. Unless JS is different, or unless we compile to some other thing, I see no practical way to do anything about this. If there is some concrete proposal, we can talk about that in a new issue.

[blogscot]

Is this problem described above really a limitation of JS?

Chrome Output:

a = 2329871239
2329871239
a = 232987123992349237492734987234897239472394729347289
2.3298712399234924e+50
a = 2329871239923492374927349872348972394723947293472892304892309482034802348023948023984023984230948203480239482308402340238
2.3298712399234923e+120

Elm repl output

λ elm-repl
---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 2329871239
-1965096057 : number
> a = 232987123992349237492734987234897239472394729347289
-1140926247 : number
> a = 2329871239923492374927349872348972394723947293472892304892309482034802348023948023984023984230948203480239482308402340238
179298702 : number

Iain

[blogscot]

Is this problem described above really a limitation of JS?

Chrome Output:

a = 2329871239
2329871239
a = 232987123992349237492734987234897239472394729347289
2.3298712399234924e+50
a = 2329871239923492374927349872348972394723947293472892304892309482034802348023948023984023984230948203480239482308402340238
2.3298712399234923e+120

Elm repl output

λ elm-repl
---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 2329871239
-1965096057 : number
> a = 232987123992349237492734987234897239472394729347289
-1140926247 : number
> a = 2329871239923492374927349872348972394723947293472892304892309482034802348023948023984023984230948203480239482308402340238
179298702 : number

Iain

[blogscot]

Ubuntu blows up after 18 steps:

---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 10
10 : number
> a = 100
100 : number
> a = 1000
1000 : number
> a = 10000
10000 : number
> a = 100000
100000 : number
> a = 1000000
1000000 : number
> a = 10000000
10000000 : number
> a = 100000000
100000000 : number
> a = 1000000000
1000000000 : number
> a = 10000000000
10000000000 : number
> a = 100000000000
100000000000 : number
> a = 1000000000000
1000000000000 : number
> a = 10000000000000
10000000000000 : number
> a = 100000000000000
100000000000000 : number
> a = 1000000000000000
1000000000000000 : number
> a = 10000000000000000
10000000000000000 : number
> a = 100000000000000000
100000000000000000 : number
> a = 1000000000000000000
1000000000000000000 : number
> a = 10000000000000000000
-8446744073709552000 : number

Windows blows up after 9 steps:

λ elm-repl
---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 10
10 : number
> a = 100
100 : number
> a = 1000
1000 : number
> a = 10000
10000 : number
> a = 100000
100000 : number
> a = 1000000
1000000 : number
> a = 10000000
10000000 : number
> a = 100000000
100000000 : number
> a = 1000000000
1000000000 : number
> a = 10000000000
1410065408 : number
> a = 100000000000
1215752192 : number
> a = 1000000000000
-727379968 : number

[blogscot]

Ubuntu blows up after 18 steps:

---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 10
10 : number
> a = 100
100 : number
> a = 1000
1000 : number
> a = 10000
10000 : number
> a = 100000
100000 : number
> a = 1000000
1000000 : number
> a = 10000000
10000000 : number
> a = 100000000
100000000 : number
> a = 1000000000
1000000000 : number
> a = 10000000000
10000000000 : number
> a = 100000000000
100000000000 : number
> a = 1000000000000
1000000000000 : number
> a = 10000000000000
10000000000000 : number
> a = 100000000000000
100000000000000 : number
> a = 1000000000000000
1000000000000000 : number
> a = 10000000000000000
10000000000000000 : number
> a = 100000000000000000
100000000000000000 : number
> a = 1000000000000000000
1000000000000000000 : number
> a = 10000000000000000000
-8446744073709552000 : number

Windows blows up after 9 steps:

λ elm-repl
---- elm-repl 0.17.1 -----------------------------------------------------------
 :help for help, :exit to exit, more at <https://github.com/elm-lang/elm-repl>
--------------------------------------------------------------------------------
> a = 10
10 : number
> a = 100
100 : number
> a = 1000
1000 : number
> a = 10000
10000 : number
> a = 100000
100000 : number
> a = 1000000
1000000 : number
> a = 10000000
10000000 : number
> a = 100000000
100000000 : number
> a = 1000000000
1000000000 : number
> a = 10000000000
1410065408 : number
> a = 100000000000
1215752192 : number
> a = 1000000000000
-727379968 : number

[lukewestby]

@evancz it looks like some part of this issue does have to do with the compiler. compiling this Elm:

module Main exposing (..)

a =
    1000000000000000000000

results in this JavaScript:

var _user$project$Main$a = 3875820019684212736;

I'm going to open a bug on the compiler

There's a bug on elm-compiler about this already: elm/compiler#1246

[lukewestby]

@evancz it looks like some part of this issue does have to do with the compiler. compiling this Elm:

module Main exposing (..)

a =
    1000000000000000000000

results in this JavaScript:

var _user$project$Main$a = 3875820019684212736;

I'm going to open a bug on the compiler

There's a bug on elm-compiler about this already: elm/compiler#1246