1 files changed, 77 insertions, 0 deletions
diff --git a/test/math/eexp.c b/test/math/eexp.c
new file mode 100644
index 000000000..dd2a64e1c
--- /dev/null
+++ b/test/math/eexp.c
@@ -0,0 +1,77 @@
+/*							xexp.c		*/
+/* exponential function check routine */
+/* by Stephen L. Moshier. */
+
+
+#include "ehead.h"
+
+/*
+extern int powinited;
+extern short maxposint[], maxnegint[];
+*/
+
+void eexp( x, y )
+unsigned short *x, *y;
+{
+unsigned short num[NE], den[NE], x2[NE];
+long i;
+unsigned short sign, expchk;
+
+/* range reduction theory: x = i + f, 0<=f<1;
+ * e**x = e**i * e**f 
+ * e**i = 2**(i/log 2).
+ * Let i/log2 = i1 + f1, 0<=f1<1.
+ * Then e**i = 2**i1 * 2**f1, so
+ * e**x = 2**i1 * e**(log 2 * f1) * e**f.
+ */
+/*
+if( powinited == 0 )
+	initpow();
+*/
+if( ecmp(x, ezero) == 0 )
+	{
+	emov( eone, y );
+	return;
+	}
+emov(x, x2);
+expchk = x2[NE-1];
+sign = expchk & 0x8000;
+x2[NE-1] &= 0x7fff;
+
+/* Test for excessively large argument */
+expchk &= 0x7fff;
+if( expchk > (EXONE + 15) )
+	{
+	eclear( y );
+	if( sign == 0 )
+		einfin( y );
+	return;
+	}
+
+eifrac( x2, &i, num );		/* x = i + f		*/
+
+if( i != 0 )
+ {
+ ltoe( &i, den );		/* floating point i	*/
+ ediv( elog2, den, den );	/* i/log 2		*/
+ eifrac( den, &i, den );	/* i/log 2  =  i1 + f1	*/
+ emul( elog2, den, den );	/* log 2 * f1		*/
+ eadd( den, num, x2 );		/* log 2 * f1  + f	*/
+ }
+
+/*x2[NE-1] -= 1;*/
+eldexp( x2, -1L, x2 ); /* divide by 2 */
+etanh( x2, x2 );	/* tanh( x/2 )			*/
+eadd( x2, eone, num );	/* 1 + tanh			*/
+eneg( x2 );
+eadd( x2, eone, den );	/* 1 - tanh			*/
+ediv( den, num, y );	/* (1 + tanh)/(1 - tanh)	*/
+
+/*y[NE-1] += i;*/
+if( sign )
+	{
+	ediv( y, eone, y );
+	i = -i;
+	}
+eldexp( y, i, y );	/* multiply by 2**i */
+}