Revert "SES does not take an equality test."

This reverts commit 1db8bdf82c85a490188882b810cd9c516e4f210e.

Conflicts:
	prototype/Doubt/SES.swift
	prototype/DoubtTests/SESTests.swift

prototype/Doubt/Algorithm.swift

@@ -85,7 +85,7 @@ public enum Algorithm<A, B> {
 			return f(Dictionary(elements: deleted + inserted + patched)).evaluate(equals, recur: recur)
 
 		case let .Roll(.ByIndex(a, b, f)):
-			return f(SES(a, b, recur: recur)).evaluate(equals, recur: recur)
+			return f(SES(a, b, equals: equals, recur: recur)).evaluate(equals, recur: recur)
 		}
 	}
 }

prototype/Doubt/SES.swift

@@ -1,7 +1,7 @@
 /// Computes the SES (shortest edit script), i.e. the shortest sequence of diffs (`Free<A, Patch<A>>`) for two arrays of terms (`Fix<A>`) which would suffice to transform `a` into `b`.
 ///
 /// This is computed w.r.t. an `equals` function, which computes the equality of leaf nodes within terms, and a `recur` function, which produces diffs representing matched-up terms.
-public func SES<Term, A>(a: [Term], _ b: [Term], recur: (Term, Term) -> Free<A, Patch<Term>>?) -> [Free<A, Patch<Term>>] {
+public func SES<Term, A>(a: [Term], _ b: [Term], equals: (Term, Term) -> Bool, recur: (Term, Term) -> Free<A, Patch<Term>>?) -> [Free<A, Patch<Term>>] {
 	typealias Diff = Free<A, Patch<Term>>
 
 	if a.isEmpty { return b.map { Diff.Pure(Patch.Insert($0)) } }

prototype/DoubtTests/SESTests.swift

@@ -57,7 +57,7 @@ private let c = Term.Leaf("c")
 private let d = Term.Leaf("d")
 
 private func SES(a: [Term], _ b: [Term]) -> [Diff] {
-	return SES(a, b, recur: const(nil))
+	return SES(a, b, equals: ==, recur: const(nil))
 }
 
 private func == (a: [Diff], b: [Diff]) -> Bool {