/* facf.c * * Factorial function * * * * SYNOPSIS: * * float y, facf(); * int i; * * y = facf( i ); * * * * DESCRIPTION: * * Returns factorial of i = 1 * 2 * 3 * ... * i. * fac(0) = 1.0. * * Due to machine arithmetic bounds the largest value of * i accepted is 33 in single precision arithmetic. * Greater values, or negative ones, * produce an error message and return MAXNUM. * * * * ACCURACY: * * For i < 34 the values are simply tabulated, and have * full machine accuracy. * */ /* Cephes Math Library Release 2.0: April, 1987 Copyright 1984, 1987 by Stephen L. Moshier Direct inquiries to 30 Frost Street, Cambridge, MA 02140 */ #include <math.h> /* Factorials of integers from 0 through 33 */ static float factbl[] = { 1.00000000000000000000E0, 1.00000000000000000000E0, 2.00000000000000000000E0, 6.00000000000000000000E0, 2.40000000000000000000E1, 1.20000000000000000000E2, 7.20000000000000000000E2, 5.04000000000000000000E3, 4.03200000000000000000E4, 3.62880000000000000000E5, 3.62880000000000000000E6, 3.99168000000000000000E7, 4.79001600000000000000E8, 6.22702080000000000000E9, 8.71782912000000000000E10, 1.30767436800000000000E12, 2.09227898880000000000E13, 3.55687428096000000000E14, 6.40237370572800000000E15, 1.21645100408832000000E17, 2.43290200817664000000E18, 5.10909421717094400000E19, 1.12400072777760768000E21, 2.58520167388849766400E22, 6.20448401733239439360E23, 1.55112100433309859840E25, 4.03291461126605635584E26, 1.0888869450418352160768E28, 3.04888344611713860501504E29, 8.841761993739701954543616E30, 2.6525285981219105863630848E32, 8.22283865417792281772556288E33, 2.6313083693369353016721801216E35, 8.68331761881188649551819440128E36 }; #define MAXFACF 33 extern float MAXNUMF; #ifdef ANSIC float facf( int i ) #else float facf(i) int i; #endif { if( i < 0 ) { mtherr( "facf", SING ); return( MAXNUMF ); } if( i > MAXFACF ) { mtherr( "facf", OVERFLOW ); return( MAXNUMF ); } /* Get answer from table for small i. */ return( factbl[i] ); }