Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

fix printing negative zero in JS backend #16505

Merged
merged 1 commit into from
Dec 29, 2020
Merged

fix printing negative zero in JS backend #16505

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 3 additions & 1 deletion lib/system/jssys.nim
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -495,11 +495,13 @@ proc negInt64(a: int64): int64 {.compilerproc.} =

proc nimFloatToString(a: float): cstring {.compilerproc.} =
## ensures the result doesn't print like an integer, i.e. return 2.0, not 2
# print `-0.0` properly
asm """
function nimOnlyDigitsOrMinus(n) {
return n.toString().match(/^-?\d+$/);
}
if (Number.isSafeInteger(`a`)) `result` = `a`+".0"
if (Number.isSafeInteger(`a`))
`result` = `a` === 0 && 1 / `a` < 0 ? "-0.0" : `a`+".0"
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@xflywind I just found out about Object.is, we should use it instead, it seems super useful here as well as in your copySign PR

if(Object.is(`a`, -0)) `result` = "-0.0"
else if(Number.isSafeInteger(`a`)) `result` =  `a`+".0"
else { ...

ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is

we can add the polyfill provided there for IE, if needed

(it may have other uses too, see examples: Object.is([], []); // false) which are hard to do without Object.is

Copy link
Member Author

@ringabout ringabout Dec 30, 2020 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Is Object.is better than a === 0 && 1 / a < 0?

we can add the polyfill provided there for IE, if needed

It emits more codes if we need to support IE.

I will think of it and look at whether scala.js uses Object.is.

Copy link
Member

@timotheecour timotheecour Dec 30, 2020 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Should be more efficient; the more code emitted doesn't matter for platforms other than IE as it won't be used

else {
`result` = `a`+""
if(nimOnlyDigitsOrMinus(`result`)){
Expand Down
30 changes: 30 additions & 0 deletions tests/misc/tnegativezero.nim
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
discard """
ringabout marked this conversation as resolved.
Show resolved Hide resolved
targets: "c cpp js"
"""

proc main()=
block:
let a = -0.0
doAssert $a == "-0.0"
doAssert $(-0.0) == "-0.0"

block:
let a = 0.0
when nimvm: discard ## TODO VM print wrong -0.0
else:
doAssert $a == "0.0"
doAssert $(0.0) == "0.0"

block:
let b = -0
doAssert $b == "0"
doAssert $(-0) == "0"

block:
let b = 0
doAssert $b == "0"
doAssert $(0) == "0"


static: main()
main()