Add explanatory comment for kOneUlp

pitrou · Dec 9, 2024 · b2cb305 · b2cb305
1 parent 0783571
commit b2cb305
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/cpp/src/arrow/testing/math.cc b/cpp/src/arrow/testing/math.cc
@@ -27,6 +27,9 @@
 namespace arrow {
 namespace {
 
+// `kOneUlp` is equal to 1.0 - (1.0 - nextafter(1.0, -inf)).
+// That is, it is the delta between 1.0 and the FP value immediately before 1.0.
+// We're using this value because `frexp` returns a mantissa between 0.5 and 1.0.
 template <typename Float>
 constexpr Float kOneUlp;
 template <>