parameterized IndexedArrayFun contract.

core/stdlib/std.ncl

@@ -159,7 +159,7 @@
 
  at
  : forall a. Number -> Array a -> a
- | std.contract.unstable.IndexedArrayFun
+ | std.contract.unstable.IndexedArrayFun 'Index
  | doc m%"
  Retrieves the n-th element from an array, with indices starting at 0.
 
@@ -570,7 +570,7 @@
 
  split_at
  : forall a. Number -> Array a -> { left : Array a, right : Array a }
- | std.contract.unstable.IndexedArrayFun
+ | std.contract.unstable.IndexedArrayFun 'Split
  | doc m%"
  Splits an array in two at a given index and puts all the elements
  to the left of the element at the given index (excluded) in the
@@ -1358,11 +1358,12 @@
  value
  in
 
- let ArrayIndexSecond = fun min_size label value =>
+ let ArrayIndexSecond = fun type min_size label value =>
  if %typeof% min_size == 'Number && %typeof% value == 'Array then
- if min_size >= %length% value then
+ let max_idx = type |> match { 'Index => %length% value - 1, 'Split => %length% value } in
+ if min_size > max_idx then
  let index_as_str = %to_str% min_size in
- let max_as_str = %to_str% (%length% value) in
+ let max_as_str = %to_str% max_idx in
  let note =
  if %length% value == 0 then
  "Can't index into an empty array"
@@ -1378,9 +1379,15 @@
  else
  value
  in
- DependentFun
- ArrayIndexFirst
- (fun index => ArrayIndexSecond index -> Dyn),
+ let contract
+ | [| 'Index, 'Split |] -> Dyn -> Dyn
+ = fun type label function =>
+ DependentFun
+ ArrayIndexFirst
+ (fun index => ArrayIndexSecond type index -> Dyn)
+ label
+ function
+ in contract,
 
  ArraySliceFun
  | doc m%"