/* Compute mul * atan(1/x) to prec digits of precision, and store the result in sum. Computes atan(1/x) using the formula: 1 1 1 1 atan(1/x) = --- - ---- + ---- - ---- + ... x 3x^3 5x^5 7x^7 */ mp_result arctan(mp_small radix, mp_small mul, mp_small x, mp_small prec, mp_int sum) { mpz_t t, v; mp_result res; mp_small rem, sign = 1, coeff = 1; mp_int_init(&t); mp_int_init(&v); ++prec; /* Compute mul * radix^prec * x The initial multiplication by x saves a special case in the loop for the first term of the series. */ if ((res = mp_int_expt_value(radix, prec, &t)) != MP_OK || (res = mp_int_mul_value(&t, mul, &t)) != MP_OK || (res = mp_int_mul_value(&t, x, &t)) != MP_OK) goto CLEANUP; x *= x; /* assumes x <= sqrt(MP_SMALL_MAX) */ mp_int_zero(sum); do { if ((res = mp_int_div_value(&t, x, &t, &rem)) != MP_OK) goto CLEANUP; if ((res = mp_int_div_value(&t, coeff, &v, &rem)) != MP_OK) goto CLEANUP; /* Add or subtract the result depending on the current sign (1 = add) */ if (sign > 0) res = mp_int_add(sum, &v, sum); else res = mp_int_sub(sum, &v, sum); if (res != MP_OK) goto CLEANUP; sign = -sign; coeff += 2; } while (mp_int_compare_zero(&t) != 0); res = mp_int_div_value(sum, radix, sum, NULL); CLEANUP: mp_int_clear(&v); mp_int_clear(&t); return res; }
int test_exptv(testspec_t *t, FILE *ofp) { mp_int in[3], out[1]; mp_result res, expect; int a, b; if(!parse_int_values(t, in, out, &expect)) return imath_errno = MP_BADARG, 0; if((res = mp_int_to_int(in[0], &a)) != MP_OK) return imath_errno = res, 0; if((res = mp_int_to_int(in[1], &b)) != MP_OK) return imath_errno = res, 0; if((res = mp_int_expt_value(a, b, in[2])) != expect) return imath_errno = res, 0; if(expect == MP_OK && mp_int_compare(in[2], out[0]) != 0) { mp_int_to_string(in[2], 10, g_output, OUTPUT_LIMIT); return imath_errno = OTHER_ERROR, 0; } return 1; }