layout/switch

Symbol: layout/switch

Use-case: Multi-way equality dispatch in block syntax. Lowers to switch clause lists consumed by compile/switch.

Behaviour: Does not accept peers. Header must be exactly switch VALUE: (one value expression). Inner case and else blocks are expanded by default layout/block (flat splice). layout/switch validates each child and emits:

(switch VALUE (COND-LIST BODY...) ... (else: BODY...))

Rules:

body entries must be case or else blocks only
case requires exactly one condition argument and it is passed through as the case’s condition list expression
else takes no arguments
only one else is allowed
case cannot appear after else
empty body is allowed and lowers to (switch VALUE)

Syntax:

switch VALUE:
  case COND-LIST:
    BODY
  case COND-LIST2:
    BODY
  else:
    BODY

Examples:

switch x:
  case [1]:
    "one"
  case [2 3]:
    "two-or-three"
  else:
    "meh"
;; -> (switch x ([1] "one") ([2 3] "two-or-three") (else: "meh"))

switch x:
  case [1]:
    "one"
;; -> (switch x ([1] "one"))

Also: special form switch.