refactor: pre-calculate constant

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---

Author: Planeshifter

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/lib/main.js

@@ -20,23 +20,43 @@
 
 // MODULES //
 
-var PI = require( '@stdlib/constants/float64/pi' );
 var isnan = require( '@stdlib/math/base/assert/is-nan' );
 
 
+// VARIABLES //
+
+var KURTOSIS = 0.8691773036059736; // 8*(π-3) / (π-2)²
+
+
 // MAIN //
 
 /**
 * Returns the excess kurtosis of a half-normal distribution.
 *
 * @param {PositiveNumber} sigma - scale parameter
 * @returns {number} excess kurtosis
+*
+* @example
+* var y = kurtosis( 1.0 );
+* // returns ~0.869
+*
+* @example
+* var y = kurtosis( 4.0 );
+* // returns ~0.869
+*
+* @example
+* var y = kurtosis( NaN );
+* // returns NaN
+*
+* @example
+* var y = kurtosis( 0.0 );
+* // returns NaN
 */
 function kurtosis( sigma ) {
 	if ( isnan( sigma ) || sigma <= 0.0 ) {
 		return NaN;
 	}
-	return ( 8.0 * ( PI - 3.0 ) ) / ( ( PI - 2.0 ) * ( PI - 2.0 ) );
+	return KURTOSIS;
 }
 
 

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/manifest.json

@@ -39,8 +39,7 @@
       "libpath": [],
       "dependencies": [
         "@stdlib/math/base/napi/unary",
-        "@stdlib/math/base/assert/is-nan",
-        "@stdlib/constants/float64/pi"
+        "@stdlib/math/base/assert/is-nan"
       ]
     },
     {
@@ -55,8 +54,7 @@
       "libraries": [],
       "libpath": [],
       "dependencies": [
-        "@stdlib/math/base/assert/is-nan",
-        "@stdlib/constants/float64/pi"
+        "@stdlib/math/base/assert/is-nan"
       ]
     },
     {
@@ -71,8 +69,7 @@
       "libraries": [],
       "libpath": [],
       "dependencies": [
-        "@stdlib/math/base/assert/is-nan",
-        "@stdlib/constants/float64/pi"
+        "@stdlib/math/base/assert/is-nan"
       ]
     }
   ]

lib/node_modules/@stdlib/stats/base/dists/halfnormal/kurtosis/src/main.c

@@ -18,7 +18,8 @@
 
 #include "stdlib/stats/base/dists/halfnormal/kurtosis.h"
 #include "stdlib/math/base/assert/is_nan.h"
-#include "stdlib/constants/float64/pi.h"
+
+static const double KURTOSIS = 0.8691773036059736; // 8*(π-3) / (π-2)²
 
 /**
 * Returns the excess kurtosis of a half-normal distribution with scale parameter `sigma`.
@@ -37,5 +38,5 @@ double stdlib_base_dists_halfnormal_kurtosis( const double sigma ) {
 	) {
 		return 0.0 / 0.0; // NaN
 	}
-	return ( 8.0 * ( STDLIB_CONSTANT_FLOAT64_PI - 3.0 ) ) / ( ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) * ( STDLIB_CONSTANT_FLOAT64_PI - 2.0 ) );
+	return KURTOSIS;
 }