exp(x)

Hello everyone! Hey, who's the smartest here? :) It is necessary to implement it in assembler Z80 subject function. Or maybe someone has a ready-made solution? If possible, you can complicate the task by ensuring that the program does not used RAM and worked only in ROM. Stanislav

Press RESET immediately, Stanislav! 07 Dec 02 22:55, Stanislav Yudin wrote to All: SY> Hey, who's the smartest here? :) Need to be implemented in assembly language Z80 SY> subject function. Or maybe someone has a ready-made solution? SY> If possible, you can complicate the task by ensuring that SY> the program did not use RAM and worked only in ROM. === Cut === ; These functions allow the mantissa and exponent of floating ; numbers to be manipulated separately. psect text global _frexp, _ldexp ; double frexp(value, eptr) ; double value; ; int * eptr; _frexp: push ix ld ix,0 add ix,sp ld a,(ix+7) ;get old exponent ld b,a ;save sign bit and 80h ;mask it out add a,64 ;add in bias ld d,a ;store new exponent back ld a,b ;now get exponent and 7Fh ;clea sign bit sub 64 ;remove bias ld l,(ix+8) ;get pointer ld h,(ix+9) ld(hl),a inc hl rla sbc a,a ld (hl),a ;store upper byte ld l,(ix+4) ;now get value to return ld h,(ix+5) ld e,(ix+6) ex de,hl ;already have sign in d pop ix ret _ldexp: push ix ld ix,0 add ix,sp ld a,(ix+8) and 7Fh ld c,a ld a,(ix+7) ld h,a and 80h ld b,a ld a,h add a,c and 7Fh or b ld h,a ld l,(ix+6) ld d,(ix+5) ld e,(ix+4) pop ix ret === Cut === double eval_poly(x, d, n) double x, d[]; int n; { int i; double res; res = d[i = n]; while(i) res = x * res + d[--i]; return res; } double log(x) double x; { int exp; static double coeff[] = { 0.0000000000, /* a0 */ 0.9999964239, /* a1 */ -0.4998741238, /* a2 */ 0.3317990258, /* a3 */ -0.2407338084, /* a4 */ 0.1676540711, /* a5 */ -0.0953293897, /* a6 */ 0.0360884937, /* a7 */ -0.0064535442, /* a8 */ }; /* zero or -ve arguments are not defined */ if(x <= 0.0) return 0.0; x = frexp(x, &exp) * 2.0 - 1.0; exp--; x = eval_poly(x, coeff, sizeof coeff/sizeof coeff[0] - 1); return x + 0.69314718055995 * exp; } double log10(x) double x; { return log(x) * 0.4342944819; } double exp(x) double x; { int exp; char sign; static double coeff[] = { 1.0000000000e+00, 6.9314718056e-01, 2.4022650695e-01, 5.5504108945e-02, 9.6181261779e-03, 1.3333710529e-03, 1.5399104432e-04, 1.5327675257e-05, 1.2485143336e-06, 1.3908092221e-07, }; if(x == 0.0) return 1.0; sign = x < 0.0; if(sign) x = -x; x *= 1.4426950409; /* convert to log2 */ exp = (int)floor(x); x -= (double)exp; x = ldexp(eval_poly(x, coeff, sizeof coeff/sizeof coeff[0] - 1), exp); if(sign) return 1.0/x; return x; } double pow(x, y) double x, y; { if(y == 0.0) return 1.0; if(x < 0.0) return 0.0; if(x == 0.0) return 0.0; x = exp(log(x) * y); return x; }