tpl/math: Add math.Rand template function

Closes #11833

tpl/math/init.go

@@ -115,6 +115,13 @@ func init() {
 			},
 		)
 
+		ns.AddMethodMapping(ctx.Rand,
+			nil,
+			[][2]string{
+				{"{{ math.Rand }}", "0.6312770459590062"},
+			},
+		)
+
 		ns.AddMethodMapping(ctx.Round,
 			nil,
 			[][2]string{

tpl/math/math.go

@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"math/rand"
 	"reflect"
 	"sync/atomic"
 
@@ -157,6 +158,11 @@ func (ns *Namespace) Pow(n1, n2 any) (float64, error) {
 	return math.Pow(af, bf), nil
 }
 
+// Rand returns, as a float64, a pseudo-random number in the half-open interval [0.0,1.0).
+func (ns *Namespace) Rand() float64 {
+	return rand.Float64()
+}
+
 // Round returns the integer nearest to n, rounding half away from zero.
 func (ns *Namespace) Round(n any) (float64, error) {
 	xf, err := cast.ToFloat64E(n)