[PATCH] Fix bug in evaluation of real and imaginary parts of powers.

Be more careful when simplifying Re(a^c) -> a^c and Im(a^c) -> 0.

Thanks to Jan Rheinländer for reporting this.

diff --git a/ginac/power.cpp b/ginac/power.cpp
index 2619492805b58ad5d635f2d8fd67bfa0706c1281..a45e1fa3ef8930c25c177569b92c3bbce61e4b31 100644 (file)
--- a/ginac/power.cpp
+++ b/ginac/power.cpp
@@ -669,7 +669,8 @@ ex power::real_part() const
        // basis == a+I*b, exponent == c+I*d
        const ex a = basis.real_part();
        const ex c = exponent.real_part();
        // basis == a+I*b, exponent == c+I*d
        const ex a = basis.real_part();
        const ex c = exponent.real_part();

-       if (basis.is_equal(a) && exponent.is_equal(c)) {
+       if (basis.is_equal(a) && exponent.is_equal(c) &&
+           (a.info(info_flags::nonnegative) || c.info(info_flags::integer))) {

                // Re(a^c)
                return *this;
        }
                // Re(a^c)
                return *this;
        }


@@ -704,7 +705,8 @@ ex power::imag_part() const
        // basis == a+I*b, exponent == c+I*d
        const ex a = basis.real_part();
        const ex c = exponent.real_part();
        // basis == a+I*b, exponent == c+I*d
        const ex a = basis.real_part();
        const ex c = exponent.real_part();

-       if (basis.is_equal(a) && exponent.is_equal(c)) {
+       if (basis.is_equal(a) && exponent.is_equal(c) &&
+           (a.info(info_flags::nonnegative) || c.info(info_flags::integer))) {

                // Im(a^c)
                return 0;
        }
                // Im(a^c)
                return 0;
        }