1 files changed, 5 insertions, 0 deletions
diff --git a/fourier.c b/fourier.c
index e52bce8..af81436 100644
--- a/fourier.c
+++ b/fourier.c
@@ -15,6 +15,11 @@
 ** FOURIER COEFFICIENTS **
 *************************/
 
+/* M_PI isn't defined if compiled with -ansi */
+#ifndef M_PI
+#define M_PI 3.14159265358979323846  /* pi */
+#endif
+
 static clock_t DoFPUTransIteration(double *abase,
 		double *bbase,
 		unsigned long arraysize);