A sequence library normally returns new sequences. There is no allocator, so
every one of these mutates the storage it was handed and a slice is the handle
that makes that useful: (slice grid 4 9) is ptr+len into grid, so sorting it
sorts those five elements and leaves the rest of grid alone. The test asserts
exactly that — it sorts a subslice and prints the whole owning array — because
it is the property that would die silently the day a slice parameter started
being copied rather than passed by value, and -O2's mem2reg would hide it.
Insertion sort rather than anything faster. Quicksort wants a stack and
mergesort wants a buffer, and neither exists; insertion sort needs a swap and
two indices. It is also the only one of the three whose inner loop is short
enough to read, which matters more than the asymptotics on the slice sizes a
frame loop actually sorts. The `and` guarding it short-circuits, and that is
load-bearing: at j = 0 the left test fails and (at s -1) is never evaluated,
so the bounds check never fires.
Over [i32] and nothing else. There are no generics, so a second element type
is a second copy of all seven functions emitted into every program that links
the prelude, and i32 is the type indices, ids and tile values already have.
An f32 set waits for a program that wants one.
min-i32 and max-i32 return (Option i32) rather than a sentinel because there
is no i32 that means "the slice was empty" and is not also a possible element.
sum-i32 accumulates in i64 and widens each element explicitly — there is no
implicit widening anywhere, and an i32 total over a screenful of i32 is how a
sum wraps without anyone noticing.
Joseph Ferano
84e170b349