Purpose of this library

[Kleidukos]

Hi, I'm reading the documentation of this library and I have a hard time determining the purpose of the Pos datatype, compared to Word. Is there some advantage that I missed?

[gbwey]

Good question. The main difference with Word is that Pos doesn't allow zero and does not provide a Num instance.
I excluded the Num instance so there would be fewer potential runtime errors arising from using fromIntegral/subtraction/negation.

Pos is designed to work with nonempty containers and in configuration where zero is invalid.
Examples:

• The cybus package uses the Pos type with multidimensional arrays and indices where each dimension of the array is nonzero and the number of dimensions is nonzero
• It is also used in the primus package for dealing with nonempty containers.
• I use it in configuration where the number of cpus cannot be zero when running concurrent tasks; or where duration of a thread delay must be greater than zero.

Not having a Num instance for Pos is annoying, but the primus package provides a Num1 class that is a safer alternative to Num that respects the bounds of those numbers. So there are Num1 instances for Natural/Word/Pos etc.

[Kleidukos]

Awesome, thank you very much for this explanation!

[gbwey]

Glad that helped.