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add ncr and npr

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chendotjs
2017-03-26 22:30:08 +08:00
parent 8cc2313ea4
commit f11d02f9a9
2 changed files with 52 additions and 8 deletions
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19
tinyexpr.c
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@@ -125,7 +125,7 @@ static double fac(double a) {/* simplest version of fac */
if (a > UINT_MAX)
return INFINITY;
unsigned int ua = (unsigned int)(a);
unsigned long int result = 1, i = 1;
unsigned long int result = 1, i;
for (i = 1; i <= ua; i++) {
if (i > ULONG_MAX / result)
return INFINITY;
@@ -133,6 +133,21 @@ static double fac(double a) {/* simplest version of fac */
}
return (double)result;
}
static double ncr(double n, double r) {
if (n < 0.0 || r < 0.0 || n < r) return NAN;
if (n > UINT_MAX || r > UINT_MAX) return INFINITY;
unsigned long int un = (unsigned int)(n), ur = (unsigned int)(r), i;
unsigned long int result = 1;
if (ur > un / 2) ur = un - ur;
for (i = 1; i <= ur; i++) {
if (result > ULONG_MAX / (un - ur + i))
return INFINITY;
result *= un - ur + i;
result /= i;
}
return result;
}
static double npr(double n, double r) {return ncr(n, r) * fac(r);}
static const te_variable functions[] = {
/* must be in alphabetical order */
@@ -155,6 +170,8 @@ static const te_variable functions[] = {
{"log", log10, TE_FUNCTION1 | TE_FLAG_PURE, 0},
#endif
{"log10", log10, TE_FUNCTION1 | TE_FLAG_PURE, 0},
{"ncr", ncr, TE_FUNCTION2 | TE_FLAG_PURE, 0},
{"npr", npr, TE_FUNCTION2 | TE_FLAG_PURE, 0},
{"pi", pi, TE_FUNCTION0 | TE_FLAG_PURE, 0},
{"pow", pow, TE_FUNCTION2 | TE_FLAG_PURE, 0},
{"sin", sin, TE_FUNCTION1 | TE_FLAG_PURE, 0},