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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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53
func.c
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@@ -2192,6 +2192,55 @@ f_log(int count, VALUE **vals)
}
S_FUNC VALUE
f_log2(int count, VALUE **vals)
{
VALUE result;
COMPLEX ctmp, *c;
NUMBER *err;
/* initialize VALUE */
result.v_subtype = V_NOSUBTYPE;
err = conf->epsilon;
if (count == 2) {
if (vals[1]->v_type != V_NUM)
return error_value(E_LOG2_1);
err = vals[1]->v_num;
}
switch (vals[0]->v_type) {
case V_NUM:
if (!qisneg(vals[0]->v_num) &&
!qiszero(vals[0]->v_num)) {
result.v_num = qlog2(vals[0]->v_num, err);
result.v_type = V_NUM;
return result;
}
ctmp.real = vals[0]->v_num;
ctmp.imag = qlink(&_qzero_);
ctmp.links = 1;
c = c_log2(&ctmp, err);
break;
case V_COM:
c = c_log2(vals[0]->v_com, err);
break;
default:
return error_value(E_LOG2_2);
}
if (c == NULL) {
return error_value(E_LOG2_3);
}
result.v_type = V_COM;
result.v_com = c;
if (cisreal(c)) {
result.v_num = qlink(c->real);
result.v_type = V_NUM;
comfree(c);
}
return result;
}
S_FUNC VALUE
f_cos(int count, VALUE **vals)
{
@@ -10165,10 +10214,8 @@ STATIC CONST struct builtin builtins[] = {
"hypotenuse of right triangle within accuracy c"},
{"ilog", 2, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_2 = f_ilog},
"integral log of a to integral base b"},
#if 0 /* XXX - to be added later */
{"ilogn", 2, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_2 = f_ilog},
"same is ilog"},
#endif /* XXX */
{"ilog10", 1, 1, 0, OP_NOP, {.null = NULL}, {.valfunc_1 = f_ilog10},
"integral log of a number base 10"},
{"ilog2", 1, 1, 0, OP_NOP, {.null = NULL}, {.valfunc_1 = f_ilog2},
@@ -10268,6 +10315,8 @@ STATIC CONST struct builtin builtins[] = {
"natural logarithm of value a within accuracy b"},
{"log", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_log},
"base 10 logarithm of value a within accuracy b"},
{"log2", 1, 2, 0, OP_NOP, {.null = NULL}, {.valfunc_cnt = f_log2},
"base 2 logarithm of value a within accuracy b"},
{"lowbit", 1, 1, 0, OP_LOWBIT, {.null = NULL}, {.null = NULL},
"low bit number in base 2 representation"},
{"ltol", 1, 2, FE, OP_NOP, {.numfunc_2 = f_legtoleg}, {.null = NULL},