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Version: 0.3

Branching

branch routes a tagged union to different handlers based on its kind discriminant. Each case handler receives the unwrapped payload — not the full { kind, value } wrapper.

Basic branching​

From demos/convert-folder-to-ts/handlers/type-check-fix.ts:

export const typeCheckFix = loop((recur) =>
  pipe(typeCheck, classifyErrors).branch({
    HasErrors: pipe(forEach(fix).drop(), recur),
    Clean: drop,
  }),
);

classifyErrors returns a tagged union — either { kind: "HasErrors", value: string[] } or { kind: "Clean", value: void }. The HasErrors handler receives the string[] of errors directly; the Clean handler receives void.

Branching with Result types​

Result combinators like .unwrapOr() are built on branch internally. You can also branch on Results explicitly:

pipe(
  riskyStep,
  branch({
    Ok: processSuccess,
    Err: handleFailure,
  }),
)

Branching with Option types​

The same pattern works for Option<T>:

pipe(
  maybeFind,
  branch({
    Some: processFound,
    None: constant("not found"),
  }),
)