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add log2(x [,eps]) builtin function

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Added log2(x [,eps]) builtin function.  When x is an integer
power of 2, log2(x) will return an integer, otherwise it will
return the equivalent of ln(x)/ln(2).
This commit is contained in:
Landon Curt Noll
2023-08-27 19:02:37 -07:00
parent 56c568060a
commit 4e5fcc8812
15 changed files with 429 additions and 71 deletions
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64
comfunc.c
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@@ -1,7 +1,7 @@
/*
* comfunc - extended precision complex arithmetic non-primitive routines
*
* Copyright (C) 1999-2007,2021-2023 David I. Bell and Ernest Bowen
* Copyright (C) 1999-2007,2021-2023 David I. Bell, Landon Curt Noll and Ernest Bowen
*
* Primary author: David I. Bell
*
@@ -39,9 +39,13 @@
*/
STATIC COMPLEX *cln_10 = NULL;
STATIC NUMBER *cln_10_epsilon = NULL;
STATIC COMPLEX *cln_2 = NULL;
STATIC NUMBER *cln_2_epsilon = NULL;
STATIC NUMBER _q10_ = { { _tenval_, 1, 0 }, { _oneval_, 1, 0 }, 1, NULL };
STATIC NUMBER _q2_ = { { _twoval_, 1, 0 }, { _oneval_, 1, 0 }, 1, NULL };
STATIC NUMBER _q0_ = { { _zeroval_, 1, 0 }, { _oneval_, 1, 0 }, 1, NULL };
COMPLEX _cten_ = { &_q10_, &_q0_, 1 };
COMPLEX _ctwo_ = { &_q2_, &_q0_, 1 };
/*
@@ -530,6 +534,7 @@ c_ln(COMPLEX *c, NUMBER *epsilon)
return r;
}
/*
* Calculate base 10 logarithm by:
*
@@ -546,7 +551,7 @@ c_log(COMPLEX *c, NUMBER *epsilon)
* compute ln(c) first
*/
ln_c = c_ln(c, epsilon);
/* log(1) == 0 */
/* quick return for log(1) == 0 */
if (ciszero(ln_c)) {
return ln_c;
}
@@ -585,6 +590,61 @@ c_log(COMPLEX *c, NUMBER *epsilon)
}
/*
* Calculate base 2 logarithm by:
*
* log(c) = ln(c) / ln(2)
*/
COMPLEX *
c_log2(COMPLEX *c, NUMBER *epsilon)
{
int need_new_cln_2 = true; /* false => use cached cln_2 value */
COMPLEX *ln_c; /* ln(x) */
COMPLEX *ret; /* base 2 of x */
/*
* compute ln(c) first
*/
ln_c = c_ln(c, epsilon);
/* quick return for log(1) == 0 */
if (ciszero(ln_c)) {
return ln_c;
}
/*
* save epsilon for ln(2) if needed
*/
if (cln_2_epsilon == NULL) {
/* first time call */
cln_2_epsilon = qcopy(epsilon);
} else if (qcmp(cln_2_epsilon, epsilon) == true) {
/* replaced cached value with epsilon arg */
qfree(cln_2_epsilon);
cln_2_epsilon = qcopy(epsilon);
} else if (cln_2 != NULL) {
/* the previously computed ln(2) is OK to use */
need_new_cln_2 = false;
}
/*
* compute ln(2) if needed
*/
if (need_new_cln_2 == true) {
if (cln_2 != NULL) {
comfree(cln_2);
}
cln_2 = c_ln(&_ctwo_, cln_2_epsilon);
}
/*
* return ln(c) / ln(2)
*/
ret = c_div(ln_c, cln_2);
comfree(ln_c);
return ret;
}
/*
* Calculate the complex cosine within the specified accuracy.
* This uses the formula: