--- we create a list from the array elements and convert them into a list using
--- `PrelPArr.toP'
---
--- * the main disadvantage to this scheme is that `toP' traverses the list
--- twice: once to determine the length and a second time to put to elements
--- into the array; this inefficiency could be avoided by exposing some of
--- the innards of `PrelPArr' to the compiler (ie, have a `PrelPArrBase') so
--- that we can exploit the fact that we already know the length of the array
--- here at compile time
+-- We desugar [:x1, ..., xn:] as
+-- singletonP x1 +:+ ... +:+ singletonP xn