From: Jim Pryor <profjim@jimpryor.net>
Date: Sat, 16 Oct 2010 18:05:49 +0000 (-0400)
Subject: alternate strategy for Y1,Y2
X-Git-Url: http://lambda.jimpryor.net/git/gitweb.cgi?p=lambda.git;a=commitdiff_plain;h=d1526a5f26872825688dbd957b8f9b296ff3cf71

alternate strategy for Y1,Y2

Signed-off-by: Jim Pryor <profjim@jimpryor.net>
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+Alternate strategy for Y1, Y2
+
+*	This is (in effect) the strategy used by OCaml. The mutually recursive:
+
+	let rec
+		f x = A  ; A may refer to f or g
+	and
+		g y = B  ; B may refer to f or g
+	in
+		C
+
+is implemented using regular, non-mutual recursion, like this (`f'` is a variable not occurring free in `A`, `B`, or `C`):
+
+	let rec f' g x = (let f = f' g in A)
+	in let rec g y = (let f = f' g in B)
+	in let f = f' g in C
+
+or, expanded into the form we've been working with:
+
+	let f' = Y (\f' g x. (\f. A) (f' g)) in
+	let g  = Y (\g y. (\f. B) (f' g)) in
+	let f  = f' g
+