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add qispowerof2() to qfunc.c, improve log2() code

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Change zispowerof2() interaface to take a FULL ptr as the 2nd arg:
zispowerof2(ZVALUE z, FULL *log2).

Added qispowerof2(NUMBER *q, NUMBER **qlog2) to qfunc.c.

Change log2() builtin to use the new qispowerof2() internal interface.

Update LIBRARY to reflect the new zispowerof2() internal interface
and the new qispowerof2() internal interface.
This commit is contained in:
Landon Curt Noll
2023-08-27 23:50:44 -07:00
parent 4e5fcc8812
commit 4dbc4dfe9a
6 changed files with 131 additions and 89 deletions
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74
qtrans.c
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@@ -1245,78 +1245,12 @@ qlog2(NUMBER *q, NUMBER *epsilon)
/*
* special case: q is integer power of 2
*
* When q is integer power of 2, the base 2 logarithm is an integer.
* We return a base 2 logarithm that is in integer in this case.
*
* From above we know that q != 0, so we need to check that q>0.
*
* We have two cases for a power of two: a positive power of 2, and a
* negative power of 2 (i.e., 1 over a power of 2).
*/
if (qispos(q)) {
ZVALUE zlog2; /* base 2 logarithm when q is power of 2 */
/*
* case: q>0 is an integer
*/
if (qisint(q)) {
/*
* check if q is an integer power of 2
*/
if (zispowerof2(q->num, &zlog2)) {
/*
* case: q>0 is an integer power of 2
*
* Return zlog2, which is an integer power of 2 as a NUMBER.
*/
ret = qalloc();
zcopy(zlog2, &ret->num);
zfree(zlog2);
return ret;
/*
* case: integer q is not an integer power of 2
*/
} else {
/* free the zispowerof2() 2nd arg and proceed to calculate ln(q)/ln(2) */
zfree(zlog2);
}
/*
* case: q>0 is 1 over an integer
*/
} else if (qisreciprocal(q)) {
/*
* check if q is 1 over an integer power of 2
*/
if (zispowerof2(q->den, &zlog2)) {
/*
* case: q>0 is an integer power of 2
*
* Return zlog2, which is an negative integer power of 2 as a NUMBER.
*/
ret = qalloc();
zlog2.sign = !zlog2.sign; /* zlog2 = -zlog2 */
zcopy(zlog2, &ret->num);
zfree(zlog2);
return ret;
/*
* case: reciprocal q is not an integer power of 2
*/
} else {
/* free the zispowerof2() 2nd arg and proceed to calculate ln(q)/ln(2) */
zfree(zlog2);
}
}
ret = qalloc();
if (qispowerof2(q, &ret)) {
return ret;
}
qfree(ret);
/*
* compute ln(c) first