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-rw-r--r--src/complex/ctanh.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/src/complex/ctanh.c b/src/complex/ctanh.c
index 0461050d..3ba3a899 100644
--- a/src/complex/ctanh.c
+++ b/src/complex/ctanh.c
@@ -101,11 +101,13 @@ double complex ctanh(double complex z)
}
/*
+ * ctanh(+-0 + i NAN) = +-0 + i NaN
+ * ctanh(+-0 +- i Inf) = +-0 + i NaN
* ctanh(x + i NAN) = NaN + i NaN
* ctanh(x +- i Inf) = NaN + i NaN
*/
if (!isfinite(y))
- return CMPLX(y - y, y - y);
+ return CMPLX(x ? y - y : x, y - y);
/*
* ctanh(+-huge + i +-y) ~= +-1 +- i 2sin(2y)/exp(2x), using the