Use hypot to implement Complex.norm

ocaml · Dec 1, 2021 · b218ea5 · b218ea5
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diff --git a/Changes b/Changes
@@ -153,6 +153,9 @@ OCaml 4.14.0
   OCaml.
   (Damien Doligez, review by Stephen Dolan)
 
+- #10786: The implementation of Complex.norm now uses Float.hypot.
+  (Christophe Troestler, review by David Allsopp and Xavier Leroy)
+
 ### Other libraries:
 
 - #10192: Add support for Unix domain sockets on Windows and use them

diff --git a/stdlib/.depend b/stdlib/.depend
@@ -189,8 +189,10 @@ stdlib__Char.cmx : char.ml \
     stdlib__Char.cmi
 stdlib__Char.cmi : char.mli
 stdlib__Complex.cmo : complex.ml \
+    stdlib__Float.cmi \
     stdlib__Complex.cmi
 stdlib__Complex.cmx : complex.ml \
+    stdlib__Float.cmx \
     stdlib__Complex.cmi
 stdlib__Complex.cmi : complex.mli
 stdlib__Digest.cmo : digest.ml \

diff --git a/stdlib/complex.ml b/stdlib/complex.ml
@@ -48,15 +48,7 @@ let inv x = div one x
 
 let norm2 x = x.re *. x.re +. x.im *. x.im
 
-let norm x =
-  (* Watch out for overflow in computing re^2 + im^2 *)
-  let r = abs_float x.re and i = abs_float x.im in
-  if r = 0.0 then i
-  else if i = 0.0 then r
-  else if r >= i then
-    let q = i /. r in r *. sqrt(1.0 +. q *. q)
-  else
-    let q = r /. i in i *. sqrt(1.0 +. q *. q)
+let norm x = Float.hypot x.re x.im
 
 let arg x = atan2 x.im x.re