giles a019aa1edc go: eval.sx — for / break / continue / inc-dec + 7 tests [nothing] ...

Phase 4 cont. go-eval-for handles all three for-header shapes:

  for { ... }                          — infinite (cond defaults to true)
  for cond { ... }                     — while-like (init=nil, post=nil)
  for init ; cond ; post { ... }       — C-style

Implementation:
  * Run INIT (if any), extending env.
  * Loop: eval COND. If false, exit with current env.
    Eval body (a :block). Catch sentinels:
      :return-value → propagate up
      :break        → exit loop with pre-break env
      :continue     → still runs POST, then re-loops
    Otherwise: run POST, re-loop.

:break and :continue propagate as keyword sentinels through
go-eval-block alongside the existing :return-value sentinel. The
block returns whichever sentinel hit first; control-flow constructs
(for, switch, select) catch them.

inc-dec (x++ / x--) updates env via the same shadowing model used by
assign — `(go-env-extend env name (+ current 1))`.

**Iterative fact(5) = 120 and the classic sum-to-9 = 45 both
evaluate.** Demonstrates the for-loop machinery is solid enough for
real programs.

eval 40/40, total 417/417.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2026-05-27 21:22:34 +00:00

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