10965: extended normalDistribution domain support to +/-inf (#10966)

tedgin · web-flow · commit 12eb40b29556 · 2026-03-01T06:32:55.000+08:00
diff --git a/std/internal/math/errorfunction.d b/std/internal/math/errorfunction.d
@@ -984,6 +984,9 @@ Journal of Statistical Software <b>11</b>, (July 2004).
 */
 real normalDistributionImpl(real a)
 {
+    if (a is -real.infinity) return 0.0L;
+    if (a is real.infinity) return 1.0L;
+
     real x = a * SQRT1_2;
     real z = fabs(x);
 
@@ -1005,6 +1008,8 @@ real normalDistributionImpl(real a)
 {
 assert(fabs(normalDistributionImpl(1L) - (0.841344746068543L)) < 0.0000000000000005L);
 assert(isIdentical(normalDistributionImpl(NaN(0x325)), NaN(0x325)));
+assert(normalDistributionImpl(-real.infinity) == 0.0L);
+assert(normalDistributionImpl(real.infinity) == 1.0L);
 }
 
 /*

Original file line number	Diff line number	Diff line change
`@@ -984,6 +984,9 @@ Journal of Statistical Software <b>11</b>, (July 2004).`
`984`	`984`	`*/`
`985`	`985`	`real normalDistributionImpl(real a)`
`986`	`986`	`{`
	`987`	`+ if (a is -real.infinity) return 0.0L;`
	`988`	`+ if (a is real.infinity) return 1.0L;`
	`989`	`+`
`987`	`990`	`real x = a * SQRT1_2;`
`988`	`991`	`real z = fabs(x);`
`989`	`992`
`@@ -1005,6 +1008,8 @@ real normalDistributionImpl(real a)`
`1005`	`1008`	`{`
`1006`	`1009`	`assert(fabs(normalDistributionImpl(1L) - (0.841344746068543L)) < 0.0000000000000005L);`
`1007`	`1010`	`assert(isIdentical(normalDistributionImpl(NaN(0x325)), NaN(0x325)));`
	`1011`	`+assert(normalDistributionImpl(-real.infinity) == 0.0L);`
	`1012`	`+assert(normalDistributionImpl(real.infinity) == 1.0L);`
`1008`	`1013`	`}`
`1009`	`1014`
`1010`	`1015`	`/*`