Spec: about index argument in iteratee

[samber]

Go does not support optional arguments. We have to duplicate helpers if we want to make the index int argument optional.

I'm opening this issue to discuss a new standard for naming helpers.

• lo.Map(list, func(item T) U -> no index
• lo.MapI(list, func(item T, index int) U -> index

The I suffix might not be comprehensible. I would suggest WithIndex as second choice.

It might introduce a large breaking change because Map and Filter are concerned. (see discussion about v2: #578)

Also, I wonder what would be the best type for this index:

• int is simple
• int64 for larger collections (useless 99.9% of time)
• uint64 the most accurate type

Don't forget that passing a function to a helpers is a very developer-friendly API: lo.Map(collection, aFunc). Since int is the most used type it seems valuable to avoid any exotic typing and cast.

Linking issues & PR: #565

[quantumsheep]

Also, I wonder what would be the best type for this index

int is the one used to identify slices index. The others would mean applying a manual conversion.

[loggerhead]

I think naming as lo.Map2 is better then lo.MapI, as it reminds the user that there are two arguments needed. Also, for lo.MapKeys and lo.MapValues, in most of my use cases, the second argument is useless.

[gurgeous]

I think MapWithIndex is a great name. This is very similar to the ruby convention.