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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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39
LIBRARY
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@@ -393,12 +393,6 @@ ZVALUE yourself. Examples of such checks are:
zge32b(z) (number is >= 2^32)
zge64b(z) (number is >= 2^64)
Return true if z an integer power of 2: set zlog2 to log base 2 of z.
Return false if a is NOT integer power of 2: set zlog2 to 0.
The zlog2 arg must be a non-NULL pointer to a ZVALUE.
zispowerof2(z, &zlog2)
Typically the largest unsigned long is typedefed to FULL. The following
macros are useful in dealing with this data type:
@@ -426,6 +420,18 @@ The zrel function tests the relative sizes of two ZVALUEs, returning -1 if
the first one is smaller, 0 if they are the same, and 1 if the first one
is larger.
To determine if z is an integer power of 2, use zispowerof2:
ZVALUE z; /* value to check if it is a power of */
FULL log2; /* set to log base 2 of z when is_power_of_2 is true */
bool is_power_of_2;
is_power_of_2 = zispowerof2(z, &log2)
Returns true if z an integer power of 2: set log2 to log base 2 of z.
Returns false if z is NOT integer power of 2 and leave log2 untouched.
The log2 arg must be a non-NULL pointer to a ZVALUE.
---------------
USING FRACTIONS
---------------
@@ -459,11 +465,12 @@ a number into the corresponding NUMBER. The str2q function accepts input in
integral, fractional, real, or exponential formats. Examples of allocating
numbers are:
NUMBER *q1, *q2, *q3;
NUMBER *q1, *q2, *q3, *q4;
q1 = itoq(66L);
q2 = iitoq(2L, 3L);
q3 = str2q("456.78");
q4 = utoq((FULL) 1234567890L);
Also unlike ZVALUEs, NUMBERs are quickly copied. This is because they contain
a link count, which is the number of pointers there are to the NUMBER. The
@@ -479,11 +486,13 @@ the ZVALUEs contained within the NUMBER, and then puts the NUMBER structure
onto a free list for quick reuse. The following is an example of allocating
NUMBERs, copying them, adding them, and finally deleting them again.
NUMBER *q1, *q2, *q3;
NUMBER *q1, *q2, *q3, *q4;
q1 = itoq(111L);
q2 = qlink(q1);
q3 = qqadd(q1, q2);
q4 = qnum(q2, q3);
qfree(q1);
qfree(q2);
qfree(q3);
@@ -544,6 +553,20 @@ These have the values 0, 1, -1, and 1/2. An example of using them is:
q1 = qlink(&_qonehalf_);
q2 = qlink(&_qone_);
To determine if q is an integer power of 2, use qispowerof2:
NUMBER *q; /* value to check if it is a power of */
NUMBER *qlog2; /* set to log base 2 of q when is_power_of_2 is true */
bool is_power_of_2;
q = utoq((FULL) 1234567890L);
qlog2 = qalloc();
is_power_of_2 = qispowerof2(q, &qlog2);
Returns true if q an integer power of 2: set *qlog2 to log base 2 of q.
Returns false if q is NOT integer power of 2 and leave *qlog2 untouched.
Use qalloc() to setup the qlog2 arg before calling.
---------------------
USING COMPLEX NUMBERS
---------------------