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Phase 7h: string slicing s[a..b] (retire substr)

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`s[a..b]` is a fresh substring of the bytes [a, b) — the modern, end-based form
of the C-style `substr(s, start, count)`:

  substr(src, start, i - start)   -> src[start..i]
  substr(t, 2, len(t) - 2)        -> t[2..len(t)]
  substr(src, i, 2)               -> src[i..i + 2]

Mechanics: a new E_SLICE postfix (`base[lo..hi]`, distinct from `base[i]`
indexing) lowers to a @fn_str_slice prelude (malloc + copy + terminate), emitted
once into any program that slices. Two reseeds: add the syntax + prelude, then
migrate the 22 substr calls and delete substr. The migrator recognises the
common `count == end - start` shape and emits the clean `s[start..end]` rather
than `s[start..start + (end - start)]`.

examples/strings.ludic gains slicing (now prints 1..9). Reseeded (22673 lines);
C-free fixpoint holds; goldens identical; 18/18; vocab + doc-fences clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Orkun ÇAKILKAYA 2026-08-28 01:35:24 +03:00
parent 0efa06dca2
commit 1b9789630a
14 changed files with 4049 additions and 3914 deletions
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30
selfhost/lex.ludic
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@ -127,25 +127,25 @@ fn lex(src: ptr) -> void {
if char_is_alpha(c) {
let start = i
while i < n and char_is_alnum(peek8(src, i)) { i = i + 1 }
tok_push(TK_ID, substr(src, start, i - start), 0, line)
tok_push(TK_ID, src[start..i], 0, line)
continue
}
if c == 59 { tok_push(TK_NL, null, 0, line); i = i + 1; continue } # ';'
# two-character operators
if two_at(src, i, 45, 62) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # ->
if two_at(src, i, 61, 62) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # =>
if two_at(src, i, 61, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # ==
if two_at(src, i, 33, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # !=
if two_at(src, i, 60, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # <=
if two_at(src, i, 62, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # >=
if two_at(src, i, 43, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # +=
if two_at(src, i, 45, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # -=
if two_at(src, i, 42, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # *=
if two_at(src, i, 47, 61) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # /=
if two_at(src, i, 46, 46) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # ..
if two_at(src, i, 60, 60) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # <<
if two_at(src, i, 62, 62) { tok_push(TK_OP, substr(src, i, 2), 0, line); i = i + 2; continue } # >>
if is_op1(c) { tok_push(TK_OP, substr(src, i, 1), 0, line); i = i + 1; continue }
if two_at(src, i, 45, 62) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # ->
if two_at(src, i, 61, 62) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # =>
if two_at(src, i, 61, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # ==
if two_at(src, i, 33, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # !=
if two_at(src, i, 60, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # <=
if two_at(src, i, 62, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # >=
if two_at(src, i, 43, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # +=
if two_at(src, i, 45, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # -=
if two_at(src, i, 42, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # *=
if two_at(src, i, 47, 61) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # /=
if two_at(src, i, 46, 46) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # ..
if two_at(src, i, 60, 60) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # <<
if two_at(src, i, 62, 62) { tok_push(TK_OP, src[i..i + 2], 0, line); i = i + 2; continue } # >>
if is_op1(c) { tok_push(TK_OP, src[i..i + 1], 0, line); i = i + 1; continue }
i = i + 1 # skip anything unrecognised
}
tok_push(TK_EOF, null, 0, line)