Merge pull request #1291 from skirpichev/fix-24684

functions: add _eval_evalf() helper for erfcinv()
diofant · Feb 13, 2023 · 793b38c · 793b38c
2 parents 273b204 + 87ebe6f
commit 793b38c
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diff --git a/diofant/functions/special/error_functions.py b/diofant/functions/special/error_functions.py
@@ -3,7 +3,7 @@
 """
 
 from ...core import (Add, EulerGamma, Function, I, Integer, Pow, Rational,
-                     cacheit, expand_mul, oo, pi, zoo)
+                     cacheit, evaluate, expand_mul, oo, pi, zoo)
 from ...core.function import ArgumentIndexError
 from ...core.sympify import sympify
 from ..combinatorial.factorials import factorial
@@ -824,6 +824,11 @@ def eval(cls, z):
     def _eval_rewrite_as_erfinv(self, z):
         return erfinv(1-z)
 
+    def _eval_evalf(self, prec):
+        with evaluate(False):
+            e = self.rewrite(erfinv)
+        return e.evalf(prec)
+
 
 class erf2inv(Function):
     r"""

diff --git a/diofant/tests/functions/test_error_functions.py b/diofant/tests/functions/test_error_functions.py
@@ -307,6 +307,9 @@ def test_erfcinv():
 
     pytest.raises(ArgumentIndexError, lambda: erfcinv(x).fdiff(2))
 
+    # issue sympy/sympy#24684
+    assert erfcinv(0.4) == 0.59511608144999484
+
 
 def test_erf2inv():
     assert erf2inv(0, 0) == 0

diff --git a/docs/release/notes-0.14.rst b/docs/release/notes-0.14.rst
@@ -122,3 +122,4 @@ These Sympy issues also were addressed:
 * :sympyissue:`24461`: sympy.polys.polyerrors.HeuristicGCDFailed: no luck -- when multiplying two Polys
 * :sympyissue:`24543`: Rational calc value error
 * :sympyissue:`6326`: PolynomialRing should not derive from CharacteristicZero
+* :sympyissue:`24684`: Unable to evaluate erfcinv