M_PI

Undocumented in source but is binding to C++. You might be able to learn more by searching the web for its name.
extern (C++)
static if(versionIsSet!("Windows") && !defined!"M_PI" && !defined!"_BSD_SOURCE" && !defined!"_GNU_SOURCE" && !defined!"_POSIX_C_SOURCE" && !defined!"_POSIX_SOURCE" && !defined!"_USE_MATH_DEFINES" && !defined!"_XOPEN_SOURCE" && !versionIsSet!("Cygwin") && defined!"__STRICT_ANSI__")
enum M_PI = (3.14159265358979323846);

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