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[Caml-list] C style for loop
- Jeff Henrikson
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| Date: | -- (:) |
| From: | Jeff Henrikson <jehenrik@y...> |
| Subject: | [Caml-list] C style for loop |
Okay, so maybe I should be more specific about what I want in a "C-style for loop." Its readablity merits are hopefully self
evident. Well, unless you're a compulsive CPS addict who wishes even his grocery list could be written to tail recurse. . .
Suppose
(* loop var | init val | while | expr for next val *)
for c 0 (c<10) (c+1) do
(* bla *)
done;
desugars into:
let rec iter_gensymXXX c =
(* bla *)
let c = (c+1) in
if (c<10) then iter_gensymXXX c else ()
in
iter_gensymXXX 0
Then we could write nice readable nested loops for square arrays, etc. And then there's the canonical loop form which enters in a
place different from the exit test. For that, C style "break" is a readable idiom:
for c 0 true c do
(* bla1 *)
let c = c+1 in
if !(c<10) then break;
(* bla2 *)
end;
could desugar into:
let rec iter_gensymXXX c =
(* bla1 *)
let c = c+1 in
if !(c<10) then
()
else begin
(* bla2 *)
let c = c in
if true then iter_gensymXXX c else ()
end
in
iter_gensymXXX 0
The transformation for "continue" is similar.
Pardon my laziness, camlp4 looks really cool, but I haven't taken the time to learn it. For the time being, if somebody has
already written a macro kind of like this, I'll take it. IMHO it would be a boon to the caml community to have a standard form for
this. Even if it were only a "style guide" addition or what have you.
Jeff Henrikson
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