Orkuncakilkaya
b798e3024e
A regular-expression library with PCRE/PECL-compatible syntax, implemented as a
Thompson NFA / Pike VM so a bad pattern from a modder can NEVER cause
catastrophic backtracking — matching is O(n·m), never exponential. `(a+)+$` on
40 non-matching chars, `(a*)*b`, `(.*a){20}b` all run in microseconds; a 50 KB
input scans in ~7 ms.
The engine (runtime/native/regex.ludic + regex_vm.ludic, ~700 lines of Ludic, no
C) parses a pattern to a small bytecode program — an unanchored lazy `.*?` prefix
makes a plain search match anywhere — and the VM runs every alive thread in
lockstep per input byte, deduped by program counter and carrying capture slots
(save/restore, leftmost-greedy priority). Supported: literals, `.`, classes
`[...]` (ranges, negation, `\d \w \s` and their negations), anchors `^ $`,
alternation `|`, capturing and `(?:…)` groups, and `* + ? {n} {n,} {n,m}` in
greedy or lazy form, plus the common escapes; numbered capture groups. Errors are
values — an invalid pattern compiles to null, never a crash. Backreferences and
look-around are out of scope for a linear engine, and on the degenerate case of a
nullable subpattern under an unbounded quantifier positions may differ from a
backtracking engine (the price of the linear-time guarantee) — documented.
Surface (Regex.*, aliased in emit_call.ludic to the regex_* functions):
compile / valid / matches / test / find / exec / next / replace / group /
group_count / start / end / ok.
The runtime is spliced on demand: the parser sets a flag when it sees `Regex.`
and maybe_splice_runtime imports the engine — so it costs nothing in a program
that doesn't use it and works in a plain tool (not just an ECS game).
Verified against Python's `re` as an oracle: a 20k-case grammar fuzzer agrees
100% on realistic patterns (0 / 15000 with capture groups) and 99.8% on group-0
spans across the full pathological grammar, the residual being the documented
nullable-quantifier case. examples/library/regex.ludic asserts the behaviour
(wired into `x test`, now 60 passed); docs: a Regex section + 13 per-symbol
pages, inventory + coverage green. Seed reseeded; the C-free bootstrap fixpoint
holds.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
26 lines
677 B
Markdown
26 lines
677 B
Markdown
---
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id: regex-valid
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name: Regex.valid
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category: regex
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kind: namespace-method
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tokens: Regex.valid
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sig: Regex.valid(pattern) -> bool
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tip: True if the pattern is well-formed (compiles without error).
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order: 2
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ns: Regex
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member: valid
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---
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A convenience over <a href="regex-compile"><code>Regex.compile</code></a>: <code>true</code> when <code>pattern</code> compiles, <code>false</code> when it is malformed. Use it to validate a user- or mod-supplied pattern before relying on it.
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Parameters:
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- `pattern` — the regular expression source
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```ludic
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program Demo {
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entry {
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if Regex.valid("(a|b)+") { print(1) }
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if not Regex.valid("(unterminated") { print(2) }
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}
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}
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```
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