Mixing gen and pipe

Effect v3.12.0

pipe and Effect.gen were introduced earlier, pipe in Composing effects ↗

Effect.gen and pipe are not rivals, they compose. Inside a generator you can still reach for pipe when one value needs a quick transform: doubles it in place, and yield* hands you the result. Use whichever reads clearest for that one line.

It works the other way too. A gen block is itself an effect, so you can pipe onto the whole thing. Here the generator sequences the two names, and a final Effect.map sits outside the block to shape its result. Reach for gen to sequence steps and pipe to transform the result, in the very same program.

import { Effect } from "effect";

// Inside gen, pipe still shines for a quick point-free transform on one value.
const program = Effect.gen(function* () {
  const doubled = yield* Effect.succeed(21).pipe(Effect.map((n) => n * 2));
  const label = yield* Effect.succeed("answer");
  return `${label}: ${doubled}`;
});
//    ^? Effect<string, never, never>

console.log(Effect.runSync(program)); // answer: 42

❚❚ beat