Fixed 3.7.1 breakage in the givens scripts examples.

Signed-off-by: Dean Wampler <[email protected]>

Author: deanwampler

src/script/scala/progscala3/contexts/typeclass/MonoidTypeClass.scala

@@ -16,7 +16,10 @@ IntMonoid.unit <+> 2              // 2
 // end::usage[]
 
 // tag::numericdefinition[]
-given NumericMonoid[T : Numeric]: Monoid[T]:
+// 2025-06-16: The following line was the original syntax in Scala 3
+// given NumericMonoid[T : Numeric]: Monoid[T]:
+// This is the currently acceptable syntax:
+given NumericMonoid: [T: Numeric] => Monoid[T]:
   def unit: T = summon[Numeric[T]].zero
   extension (t: T)
     infix def combine(other: T): T = summon[Numeric[T]].plus(t, other)
@@ -30,25 +33,6 @@ NumericMonoid[BigDecimal].unit <+> BigDecimal(3.14)
 NumericMonoid[BigDecimal].unit combine BigDecimal(3.14)
 // end::numericdefinition[]
 
-// tag::numericdefinition2[]
-given NumericMonoid[T](using num: Numeric[T]): Monoid[T]:
-  def unit: T = num.zero
-  extension (t: T)
-    infix def combine(other: T): T = num.plus(t, other)
-// end::numericdefinition2[]
-
-// tag::numericdefinition3[]
-given [T : Numeric]: Monoid[T]:
-  def unit: T = summon[Numeric[T]].zero
-  extension (t: T)
-    infix def combine(other: T): T = summon[Numeric[T]].plus(t, other)
-// or
-given [T](using num: Numeric[T]): Monoid[T]:
-  def unit: T = summon[Numeric[T]].zero
-  extension (t: T)
-    infix def combine(other: T): T = summon[Numeric[T]].plus(t, other)
-
-BigDecimal(3.14) <+> summon[Monoid[BigDecimal]].unit
-summon[Monoid[BigDecimal]].unit <+> BigDecimal(3.14)
-summon[Monoid[BigDecimal]].unit combine BigDecimal(3.14)
-// end::numericdefinition3[]
+// See MonoidTypeClass2.scala for an alternative definition.
+// We can't write it in this file because loading the script causes errors
+// with alternative definitions in scope.

src/script/scala/progscala3/contexts/typeclass/MonoidTypeClass2.scala

@@ -0,0 +1,25 @@
+// tag::usage[]
+// src/script/scala/progscala3/contexts/typeclass/MonoidTypeClass2.scala
+import progscala3.contexts.typeclass.{Monoid, given}       // <1>
+
+// 2025-06-16: This file was split off from MonoidTypeClass.scala to 
+// to eliminate errors that occur with the effectively duplicate definitions
+// of monoids for Numerics. Here, we use an anonymous given, rather than the
+// named given in the other file. Note the use of summon below.
+
+// tag::numericdefinition3[]
+given [T : Numeric] => Monoid[T]:
+  def unit: T = summon[Numeric[T]].zero
+  extension (t: T)
+    infix def combine(other: T): T = summon[Numeric[T]].plus(t, other)
+// or
+// 2025-06-16: This alternative syntax no longer works. A replacement is TBD.
+// given [T](using num: Numeric[T]): Monoid[T]:
+//   def unit: T = summon[Numeric[T]].zero
+//   extension (t: T)
+//     infix def combine(other: T): T = summon[Numeric[T]].plus(t, other)
+
+BigDecimal(3.14) <+> summon[Monoid[BigDecimal]].unit
+summon[Monoid[BigDecimal]].unit <+> BigDecimal(3.14)
+summon[Monoid[BigDecimal]].unit combine BigDecimal(3.14)
+// end::numericdefinition3[]