Provide a binding to the .toFixed API

[agrafix]

Convert a float into a string including a fixed number of decimal places. I think this is a very frequently used function when building user-interfaces so it might be good to but this in the core libraries.

[rgrempel]

According to the Mozilla documentation of toFixed, it is possible for Javascript's toFixed to throw exceptions. I suppose one wouldn't have to worry about the TypeError, since the Elm type checker will save us from that. However, there is the RangeError to consider.

So, to guarantee no runtime errors, one would have to make the return type something like a Result String String instead of just returning a string. Here's a version of the native code that returns a Result:

https://github.com/rgrempel/elm-web-api/blob/master/src/Native/WebAPI/Number.js#L31-L37

and what the interface might look like:

https://github.com/rgrempel/elm-web-api/blob/master/src/WebAPI/Number.elm#L75-L81

Or, to put it another way, you should consider this test case:

https://github.com/rgrempel/elm-web-api/blob/master/test/src/WebAPI/NumberTest.elm#L44

[rgrempel]

According to the Mozilla documentation of toFixed, it is possible for Javascript's toFixed to throw exceptions. I suppose one wouldn't have to worry about the TypeError, since the Elm type checker will save us from that. However, there is the RangeError to consider.

So, to guarantee no runtime errors, one would have to make the return type something like a Result String String instead of just returning a string. Here's a version of the native code that returns a Result:

https://github.com/rgrempel/elm-web-api/blob/master/src/Native/WebAPI/Number.js#L31-L37

and what the interface might look like:

https://github.com/rgrempel/elm-web-api/blob/master/src/WebAPI/Number.elm#L75-L81

Or, to put it another way, you should consider this test case:

https://github.com/rgrempel/elm-web-api/blob/master/test/src/WebAPI/NumberTest.elm#L44

[rgrempel]

I guess the other option, if you wanted to return a simple String instead of a Result, would be to clamp the number of digits between 0 and 20 -- at least, the Mozilla documentation suggests that an exception will not be thrown in those cases.

[rgrempel]

I guess the other option, if you wanted to return a simple String instead of a Result, would be to clamp the number of digits between 0 and 20 -- at least, the Mozilla documentation suggests that an exception will not be thrown in those cases.

[evancz]

This is added to #322 and is easy enough to add. Makes sense to make the decision before writing the code.

[evancz]

This is added to #322 and is easy enough to add. Makes sense to make the decision before writing the code.

[witoldsz]

@evancz toFixed is a really nice to have. I need to format data in a table and seeing this task as closed and referenced in #721 aka "to be done in the future" makes me sad again - yesterday I was in trouble, found the solution: #842 but it's also postponed for the same reason.

[witoldsz]

@evancz toFixed is a really nice to have. I need to format data in a table and seeing this task as closed and referenced in #721 aka "to be done in the future" makes me sad again - yesterday I was in trouble, found the solution: #842 but it's also postponed for the same reason.