fa67f300f6
This PR renames `String.ValidPos` to `String.Pos`, `String.endValidPos` to `String.endPos` and `String.startValidPos` to `String.startPos`. Accordingly, the deprecations of `String.Pos` to `String.Pos.Raw` and `String.endPos` to `String.rawEndPos` are removed early, after an abbreviated deprecation cycle of two releases.
42 lines
1.1 KiB
Text
42 lines
1.1 KiB
Text
module
|
|
|
|
-- Test that termination proofs for stepping through a string with `next` and `prev` works.
|
|
|
|
def isConsonant (i : String.Pos str) : Bool :=
|
|
match i.get! with
|
|
| 'a' | 'e' | 'i' | 'o' | 'u' => false
|
|
| 'y' =>
|
|
if h : i = str.startPos then true
|
|
else !isConsonant (i.prev h)
|
|
| _ => true
|
|
termination_by i.down
|
|
|
|
def measure₁ (word : String) : Nat :=
|
|
let rec aux (pos : String.Pos word) (inVowel : Bool) (count : Nat) : Nat :=
|
|
match h : pos.next? with
|
|
| some next =>
|
|
if !isConsonant pos then
|
|
aux next true count
|
|
else if inVowel then
|
|
aux next false (count + 1)
|
|
else
|
|
aux next false count
|
|
| none => count
|
|
termination_by pos
|
|
|
|
aux word.startPos false 0
|
|
|
|
def measure₂ (word : String) : Nat :=
|
|
let rec aux (pos : String.Pos word) (inVowel : Bool) (count : Nat) : Nat :=
|
|
if h : pos = word.endPos then count
|
|
else
|
|
let next := pos.next h
|
|
if !isConsonant pos then
|
|
aux next true count
|
|
else if inVowel then
|
|
aux next false (count + 1)
|
|
else
|
|
aux next false count
|
|
termination_by pos
|
|
|
|
aux word.startPos false 0
|