commons

halotukozak's small collection of Scala 3 macro and metaprogramming utilities: tuple operations backed by type-level constraints, and typeclass-derivation factories that make FromExpr/ToExpr derivation work recursively for generic types.

Cross-built for the JVM, Scala.js, and Scala Native. Published to Maven Central under com.halotukozak.

Installation

scala-cli:

//> using dep com.halotukozak::commons::<version>

sbt:

libraryDependencies += "com.halotukozak" %% "commons" % "<version>"

What's inside

Tuple utilities

• Tuple.to[T, C] / toArrayOf[T] — convert a tuple into any standard collection (via Factory) or a plain Array, guarded by a containsOnly constraint.
• Tuple.mapAs[T] — map over a tuple's elements with a function polymorphic in a shared upper bound T.
• Tuple.foreach, Tuple.indices, Tuple.hasDuplicates — small ergonomic additions on top of scala.Tuple.
• realCons — cons an element onto a tuple while preserving its precise singleton type.
• containsOnly[Tup, T] — a type-level constraint proving every element of Tup conforms to T, with derivation rules for Tuple.Map, covariant functors, Tail, Reverse, Concat, and Zip, plus implicit conversions from Head/Last.

Expr derivation

• FromExprFactory / ToExprFactory — derives on any product or sum type recursively derives FromExpr[T] / ToExpr[T] for each field/case, so generic types no longer need a hand-written given for their type parameters.
• Built-in instances for Array, Seq, List, Set, Map, Option, Some, Either/Left/Right, and Tuple1 through Tuple22.
• QuotedFactoryGivens bridges any derived factory back into the standard FromExpr/ToExpr so it's picked up automatically wherever those are expected.
• Expr.ofRefinedTuple — build an Expr[Tuple] from a List[Expr[?]] while keeping each element's refined type.

import scala.quoted.*

case class Point(x: Int, y: Int) derives ToExprFactory, FromExprFactory

License

MIT