(sigil fp chain)

(sigil fp chain) - Threading Macros (re-exported from core)

The threading macros chain, ->, and some-> now live in (sigil core), where they were before the 2026-03-31 FP extraction. They are structural control-flow syntax used throughout idiomatic Sigil, not optional combinators, so they belong in core. Since (sigil core) is auto-imported into every module, any program already has these macros in scope without importing anything.

This module re-exports them so existing (import (sigil fp chain)) and (import (sigil fp)) consumers keep working unchanged. Because the re-exported bindings ARE core's bindings (not fresh definitions), a program importing both (sigil core) and (sigil fp) sees no duplicate-binding conflict.

The optional combinators (compose, pipe, partial, partial-right, flip, complement, juxt, const) remain in (sigil fp fn).

Basic Threading

;; Thread-first (no placeholder needed)
(chain 5 (+ 3) (* 2))
; => 16 (same as (* (+ 5 3) 2))

;; Explicit placeholder with _
(chain '(1 2 3)
       (map (lambda (x) (* x 2)) _)
       (apply + _))
; => 12

Short-Circuit Threading

;; Returns #f if any step produces #f
(some-> user
        (dict-ref _ name:)
        (string-split " " _)
        car)