Add gmp_binomial()

Adds PHP bindings for mpz_bin_ui and mpz_bin_uiui, for calculating
binomial coefficients.

NEWS

@@ -48,6 +48,7 @@ PHP                                                                        NEWS
 
 - GMP:
   . Export internal structures and accessor helpers for GMP object. (Sara)
+  . Added gmp_binomial(n, k). (Nikita)
 
 - intl:
   . Fixed bug #75317 (UConverter::setDestinationEncoding changes source instead 

UPGRADING

@@ -85,6 +85,9 @@ Date:
   . Added the DateTime::createFromImmutable() method, which mirrors
     DateTimeImmutable::createFromMutable().
 
+GMP:
+  . Added gmp_binomial(n, k) for calculating binomial coefficients.
+
 Intl:
   . Added void Spoofchecker::setRestrictionLevel(int $level) method, available
     when linked with ICU >= 58.1. Levels are represented as class constants

ext/gmp/gmp.c

@@ -188,6 +188,7 @@ const zend_function_entry gmp_functions[] = {
 	ZEND_FE(gmp_popcount,	arginfo_gmp_unary)
 	ZEND_FE(gmp_hamdist,	arginfo_gmp_binary)
 	ZEND_FE(gmp_nextprime,	arginfo_gmp_unary)
+	ZEND_FE(gmp_binomial,	arginfo_gmp_binary)
 	PHP_FE_END
 };
 /* }}} */
@@ -1382,6 +1383,36 @@ ZEND_FUNCTION(gmp_fact)
 }
 /* }}} */
 
+/* {{{ proto GMP gmp_binomial(mixed n, int k)
+ * Calculates binomial coefficient */
+ZEND_FUNCTION(gmp_binomial)
+{
+	zval *n_arg;
+	zend_long k;
+	mpz_ptr gmpnum_result;
+
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "zl", &n_arg, &k) == FAILURE) {
+		return;
+	}
+
+	if (k < 0) {
+		php_error_docref(NULL, E_WARNING, "k cannot be negative");
+		RETURN_FALSE;
+	}
+
+	INIT_GMP_RETVAL(gmpnum_result);
+	if (Z_TYPE_P(n_arg) == IS_LONG && Z_LVAL_P(n_arg) >= 0) {
+		mpz_bin_uiui(gmpnum_result, (gmp_ulong) Z_LVAL_P(n_arg), (gmp_ulong) k);
+	} else {
+		mpz_ptr gmpnum_n;
+		gmp_temp_t temp_n;
+		FETCH_GMP_ZVAL(gmpnum_n, n_arg, temp_n);
+		mpz_bin_ui(gmpnum_result, gmpnum_n, (gmp_ulong) k);
+		FREE_GMP_TEMP(temp_n);
+	}
+}
+/* }}} */
+
 /* {{{ proto GMP gmp_pow(mixed base, int exp)
    Raise base to power exp */
 ZEND_FUNCTION(gmp_pow)

ext/gmp/php_gmp.h

@@ -78,6 +78,7 @@ ZEND_FUNCTION(gmp_testbit);
 ZEND_FUNCTION(gmp_popcount);
 ZEND_FUNCTION(gmp_hamdist);
 ZEND_FUNCTION(gmp_nextprime);
+ZEND_FUNCTION(gmp_binomial);
 
 ZEND_BEGIN_MODULE_GLOBALS(gmp)
 	zend_bool rand_initialized;

ext/gmp/tests/gmp_binomial.phpt

@@ -0,0 +1,67 @@
+--TEST--
+gmp_binomial(): Binomial coefficients
+--FILE--
+<?php
+
+var_dump(gmp_binomial(10, 5));
+var_dump(gmp_binomial("10", 5));
+$n = gmp_init(10);
+var_dump(gmp_binomial($n, 5));
+
+var_dump(gmp_binomial(10000, 100));
+
+var_dump(gmp_binomial(0, 0));
+var_dump(gmp_binomial(0, 1));
+var_dump(gmp_binomial(1, 0));
+var_dump(gmp_binomial(1, 1));
+
+var_dump(gmp_binomial(-1, 5)); // == -(1 + 5 - 1 over 5)
+var_dump(gmp_binomial(-2, 6)); // == (2 + 6 - 1 over 6)
+
+var_dump(gmp_binomial(5, -2));
+
+?>
+--EXPECTF--
+object(GMP)#1 (1) {
+  ["num"]=>
+  string(3) "252"
+}
+object(GMP)#1 (1) {
+  ["num"]=>
+  string(3) "252"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(3) "252"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(242) "65208469245472575695415972927215718683781335425416743372210247172869206520770178988927510291340552990847853030615947098118282371982392705479271195296127415562705948429404753632271959046657595132854990606768967505457396473467998111950929802400"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(1) "1"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(1) "0"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(1) "1"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(1) "1"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(2) "-1"
+}
+object(GMP)#2 (1) {
+  ["num"]=>
+  string(1) "7"
+}
+
+Warning: gmp_binomial(): k cannot be negative in %s on line %d
+bool(false)