1 files changed, 15 insertions, 0 deletions
diff --git a/libc/utils/MPFRWrapper/MPCommon.cpp b/libc/utils/MPFRWrapper/MPCommon.cpp
index 77039d4bf7df..c25522077411 100644
--- a/libc/utils/MPFRWrapper/MPCommon.cpp
+++ b/libc/utils/MPFRWrapper/MPCommon.cpp
@@ -138,6 +138,21 @@ MPFRNumber MPFRNumber::atanh() const {
   return result;
 }
 
+MPFRNumber MPFRNumber::atanpi() const {
+  MPFRNumber result(*this);
+#if MPFR_VERSION >= MPFR_VERSION_NUM(4, 2, 0)
+  mpfr_atanpi(result.value, value, mpfr_rounding);
+  return result;
+#else
+  MPFRNumber value_atan(0.0, mpfr_precision * 3);
+  mpfr_atan(value_atan.value, value, MPFR_RNDN);
+  MPFRNumber value_pi(0.0, mpfr_precision * 3);
+  mpfr_const_pi(value_pi.value, MPFR_RNDN);
+  mpfr_div(result.value, value_atan.value, value_pi.value, mpfr_rounding);
+  return result;
+#endif
+}
+
 MPFRNumber MPFRNumber::cbrt() const {
   MPFRNumber result(*this);
   mpfr_cbrt(result.value, value, mpfr_rounding);