1 files changed, 47 insertions, 0 deletions
diff --git a/lib/factorial.c b/lib/factorial.c
new file mode 100644
index 0000000..8e64fa3
--- /dev/null
+++ b/lib/factorial.c
@@ -0,0 +1,47 @@
+// Factorial
+//
+// factorial - n!
+//
+// n! = 1 * 2 * ... * n, capped at 170!
+//
+// Inputs:    1 (n)
+// Outputs:   1 (n!)
+// Constants: 0
+
+#include "ts.h"
+
+
+
+ts_parameter_t const ts_factorial_p = { .n_inputs = 1, .n_outputs = 1, .n_constants = 0, .params_size = 0 };
+
+
+uint_t ts_factorial_offset( ts_constant_t const *c )
+{
+	( void )c;
+	return ( 0 );
+}
+
+int ts_factorial(
+	fp_t * const *y, uint_t y_n,
+	fp_t const * const *x, uint_t x_n,
+	uint_t n, ts_constant_t const *c
+)
+{
+	TS_PROLOGUE( ts_factorial_p );
+	(void)c;
+	for( uint_t i = 0; i < n; ++i )
+	{
+		if (x[0][i] < 0) { y[0][i] = NAN; continue; }
+		fp_t result = 1.0;
+		uint_t k = (uint_t)x[0][i];
+		if (k > 170) k = 170;
+		for( uint_t j = 1; j <= k; ++j )
+		{
+			result *= (fp_t)j;
+		}
+		y[0][i] = result;
+	}
+	return 0;
+}
+
+