Adding a comparison combinator for pairs.

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/util.ml b/lib/util.ml
index 38d73d3453..0389336258 100644
--- a/lib/util.ml
+++ b/lib/util.ml
@@ -20,6 +20,12 @@ let on_pi1 f (a,b,c) = (f a,b,c)
 let on_pi2 f (a,b,c) = (a,f b,c)
 let on_pi3 f (a,b,c) = (a,b,f c)
 
+(* Comparing pairs *)
+
+let pair_compare cmpx cmpy (x1,y1 as p1) (x2,y2 as p2) =
+  if p1 == p2 then 0 else
+  let c = cmpx x1 x2 in if c == 0 then cmpy y1 y2 else c
+
 (* Projections from triplets *)
 
 let pi1 (a,_,_) = a