nx_smtlib_parse.nx source
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1// nx_smtlib_parse.nx -- SMT-LIB v2 parser, propositional fragment.
2//
3// Foundation for SMT-COMP entry (https://smt-comp.github.io/). SMT-LIB
4// is the canonical input format for SMT solvers (Z3, cvc5, Yices,
5// Bitwuzla). This MVP handles the QF_UF (Quantifier-Free Uninterpreted
6// Functions, Boolean-only) fragment -- enough to enter the easiest
7// SMT-COMP divisions.
8//
9// Grammar handled:
10// script ::= command*
11// command ::= "(" "set-logic" symbol ")"
12// | "(" "declare-fun" symbol "()" "Bool" ")"
13// | "(" "declare-const" symbol "Bool" ")"
14// | "(" "assert" formula ")"
15// | "(" "check-sat" ")"
16// | "(" "exit" ")"
17// formula ::= symbol -- atom
18// | "true" | "false"
19// | "(" "not" formula ")"
20// | "(" "and" formula+ ")"
21// | "(" "or" formula+ ")"
22// | "(" "=>" formula formula ")"
23// | "(" "=" formula formula ")"
24// | "(" "xor" formula formula ")"
25//
26// Output: a SatProblem (DIMACS literals) ready for nx_sat_solve.
27//
28// Theories (LIA, LRA, BV, arrays, strings) deferred to later commits;
29// each requires a dedicated theory-solver primitive.
30
31// nx_safety_envelope:
32// intended_use: AUTO_APPLIED -- primitive-specific tuning queued
33// sil_target: SIL1
34// evidence: [bulk_applied_2026-05-16, see-file-comment-for-detail]
35// verdict: NOT_YET_EVALUATED
36
37import "nx_syscalls.nx"
38import "nx_runtime.nx"
39import "nx_tier.nx"
40import "nx_str.nx"
41import "nx_result.nx"
42import "nx_file_result.nx"
43import "nx_sat_solver.nx"
44
45// ---- s-expression tokenizer ------------------------------------
46const NX_SMT_TOK_LPAREN: nx_int = 1
47const NX_SMT_TOK_RPAREN: nx_int = 2
48const NX_SMT_TOK_SYM: nx_int = 3
49const NX_SMT_TOK_EOF: nx_int = 4
50
51const NX_SMT_MAX_SYM_LEN: nx_int = 64
52const NX_SMT_MAX_VARS: nx_int = 1024
53
54struct SmtParser {
55 buf: *u8,
56 n: nx_int,
57 pos: *nx_int, // single-elem buffer
58 var_names: *u8, // [NX_SMT_MAX_VARS * NX_SMT_MAX_SYM_LEN]
59 n_vars: nx_int, // distinct Boolean vars seen
60 formula: *SatFormula,
61}
62const NX_SMT_PARSER_BYTES: nx_int = 40
63
64func nx_smt_parser_new(buf: *u8, n: nx_int) -> *SmtParser {
65 let p: *SmtParser = (sys_mmap(NX_SMT_PARSER_BYTES as i64)) as *SmtParser
66 p.buf = buf
67 p.n = n
68 p.pos = (sys_mmap(8)) as *nx_int
69 p.pos[0] = 0
70 p.var_names = sys_mmap((NX_SMT_MAX_VARS * NX_SMT_MAX_SYM_LEN) as i64)
71 p.n_vars = 0
72 p.formula = nx_sat_alloc(NX_SMT_MAX_VARS)
73 return p
74}
75
76func nx_smt_skip_ws(p: *SmtParser) {
77 var pp: nx_int = p.pos[0]
78 while pp < p.n {
79 let c: nx_int = p.buf[pp] as nx_int
80 if c == 32 { pp = pp + 1 }
81 if c == 9 { pp = pp + 1 }
82 if c == 10 { pp = pp + 1 }
83 if c == 13 { pp = pp + 1 }
84 if c == 59 { // ';' line comment
85 while pp < p.n {
86 let cc: nx_int = p.buf[pp] as nx_int
87 pp = pp + 1
88 if cc == 10 { pp = pp - 0 } // exit handled below
89 if cc == 10 { p.pos[0] = pp; nx_smt_skip_ws(p); return }
90 }
91 }
92 if c != 32 {
93 if c != 9 {
94 if c != 10 {
95 if c != 13 {
96 if c != 59 { p.pos[0] = pp; return }
97 }
98 }
99 }
100 }
101 }
102 p.pos[0] = pp
103}
104
105// Read next token; on TOK_SYM, write the symbol into out_sym and
106// return its length. out_sym is null-terminated.
107func nx_smt_next_tok(p: *SmtParser, out_sym: *u8) -> nx_int {
108 nx_smt_skip_ws(p)
109 if p.pos[0] >= p.n { return NX_SMT_TOK_EOF }
110 let c: nx_int = p.buf[p.pos[0]] as nx_int
111 if c == 40 { p.pos[0] = p.pos[0] + 1; return NX_SMT_TOK_LPAREN }
112 if c == 41 { p.pos[0] = p.pos[0] + 1; return NX_SMT_TOK_RPAREN }
113 // Symbol: any non-paren non-whitespace run.
114 var len: nx_int = 0
115 while p.pos[0] < p.n {
116 let cc: nx_int = p.buf[p.pos[0]] as nx_int
117 if cc == 40 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
118 if cc == 41 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
119 if cc == 32 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
120 if cc == 9 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
121 if cc == 10 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
122 if cc == 13 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
123 if cc == 59 { out_sym[len] = 0; return NX_SMT_TOK_SYM }
124 if len < NX_SMT_MAX_SYM_LEN - 1 {
125 out_sym[len] = p.buf[p.pos[0]]
126 len = len + 1
127 }
128 p.pos[0] = p.pos[0] + 1
129 }
130 out_sym[len] = 0
131 return NX_SMT_TOK_SYM
132}
133
134// Get/create the SAT-var-id (1-indexed) for a Boolean symbol.
135func nx_smt_var_id(p: *SmtParser, name: *u8) -> nx_int {
136 var i: nx_int = 0
137 while i < p.n_vars {
138 let stored: *u8 = ((p.var_names as nx_int) + (i * NX_SMT_MAX_SYM_LEN)) as *u8
139 if nx_str_eq(stored, name) == 1 { return i + 1 }
140 i = i + 1
141 }
142 if p.n_vars >= NX_SMT_MAX_VARS { return 0 - 1 }
143 let slot: *u8 = ((p.var_names as nx_int) + (p.n_vars * NX_SMT_MAX_SYM_LEN)) as *u8
144 let _c: *u8 = nx_str_cpy(slot, name)
145 p.n_vars = p.n_vars + 1
146 return p.n_vars
147}
148
149// Forward decl for the recursive descent.
150func nx_smt_parse_formula(p: *SmtParser) -> nx_int;
151
152// Parse a parenthesised formula starting AT the opening paren.
153// Returns the head literal of the formula's CNF translation, or 0 on
154// error. Internally adds Tseitin-style clauses when needed.
155//
156// Simplified MVP: only assertions of the form (assert (= a b)),
157// (assert a), (assert (not a)), (assert (and ...)), (assert (or ...))
158// get handled directly. Complex nested formulas with mixed
159// connectives need the full Tseitin path; for v1 we handle clauses
160// where the top-level structure is a single ASSERT of a boolean
161// combination of atoms.
162
163// Parse a single Boolean term (atom or operator-application). For
164// atoms returns a positive int (var id); for negated returns negative.
165// For complex operators returns 0 (caller should have flattened first).
166func nx_smt_parse_formula(p: *SmtParser) -> nx_int {
167 nx_smt_skip_ws(p)
168 if p.pos[0] >= p.n { return 0 }
169 let c: nx_int = p.buf[p.pos[0]] as nx_int
170
171 // Bare symbol -- atom or true/false
172 if c != 40 {
173 let sym_buf: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
174 let _t: nx_int = nx_smt_next_tok(p, sym_buf)
175 if nx_str_eq(sym_buf, "true" as *u8) == 1 {
176 // Always-true: encode as a fresh tautology var
177 let v: nx_int = nx_smt_var_id(p, "$true" as *u8)
178 return v
179 }
180 if nx_str_eq(sym_buf, "false" as *u8) == 1 {
181 let v: nx_int = nx_smt_var_id(p, "$true" as *u8)
182 return 0 - v
183 }
184 return nx_smt_var_id(p, sym_buf)
185 }
186
187 // Parenthesised: (op args...)
188 p.pos[0] = p.pos[0] + 1
189 let op_buf: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
190 let _t: nx_int = nx_smt_next_tok(p, op_buf)
191
192 // (not f)
193 if nx_str_eq(op_buf, "not" as *u8) == 1 {
194 let inner: nx_int = nx_smt_parse_formula(p)
195 nx_smt_skip_ws(p)
196 if p.pos[0] < p.n {
197 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1 }
198 }
199 return 0 - inner
200 }
201
202 // For (and ...), (or ...), (=> ...), (= ...), (xor ...) -- caller
203 // typically wraps these in an (assert ...) which we handle by
204 // emitting clauses to formula. For an embedded use, we return
205 // the literal of the first operand and let the caller deal.
206 // This MVP intentionally keeps complex formulas as Tseitin-deferred.
207 // For now, treat as: read all operand literals and just pick the
208 // first; the assert handler emits the proper clauses.
209 let first: nx_int = nx_smt_parse_formula(p)
210 var done: nx_int = 0
211 while done == 0 {
212 nx_smt_skip_ws(p)
213 if p.pos[0] >= p.n { done = 1 }
214 if done == 0 {
215 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1; done = 1 }
216 if done == 0 { let _ig: nx_int = nx_smt_parse_formula(p) }
217 }
218 }
219 return first
220}
221
222// Parse an entire (assert ...) command. Extracts the asserted formula
223// and adds appropriate SAT clauses. Supports:
224// (assert atom) -> [atom]
225// (assert (not atom)) -> [-atom]
226// (assert (or a b c)) -> [a, b, c]
227// (assert (and a b c)) -> [a], [b], [c]
228// (assert (=> a b)) -> [-a, b]
229// (assert (= a b)) -> [-a, b], [-b, a] (iff for booleans)
230//
231// Caller must position parser at the start of the formula (after
232// "assert" + ws).
233func nx_smt_handle_assert(p: *SmtParser) {
234 nx_smt_skip_ws(p)
235 if p.pos[0] >= p.n { return }
236 let c: nx_int = p.buf[p.pos[0]] as nx_int
237
238 // Bare atom: emit as unit clause.
239 if c != 40 {
240 let sym_buf: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
241 let _t: nx_int = nx_smt_next_tok(p, sym_buf)
242 let v: nx_int = nx_smt_var_id(p, sym_buf)
243 let lits: *nx_int = (sys_mmap(8)) as *nx_int
244 lits[0] = v
245 let _add: nx_int = nx_sat_add_clause(p.formula, lits, 1)
246 return
247 }
248
249 // (op args...)
250 p.pos[0] = p.pos[0] + 1
251 let op_buf: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
252 let _t: nx_int = nx_smt_next_tok(p, op_buf)
253
254 let lits: *nx_int = (sys_mmap((64 * 8) as i64)) as *nx_int
255
256 // (not atom)
257 if nx_str_eq(op_buf, "not" as *u8) == 1 {
258 let inner: nx_int = nx_smt_parse_formula(p)
259 nx_smt_skip_ws(p)
260 if p.pos[0] < p.n {
261 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1 }
262 }
263 lits[0] = 0 - inner
264 let _add: nx_int = nx_sat_add_clause(p.formula, lits, 1)
265 return
266 }
267
268 // (or a b c) -- one disjunctive clause
269 if nx_str_eq(op_buf, "or" as *u8) == 1 {
270 var n: nx_int = 0
271 var done: nx_int = 0
272 while done == 0 {
273 nx_smt_skip_ws(p)
274 if p.pos[0] >= p.n { done = 1 }
275 if done == 0 {
276 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1; done = 1 }
277 if done == 0 {
278 let l: nx_int = nx_smt_parse_formula(p)
279 if n < 64 { lits[n] = l; n = n + 1 }
280 }
281 }
282 }
283 let _add: nx_int = nx_sat_add_clause(p.formula, lits, n)
284 return
285 }
286
287 // (and a b c) -- multiple unit clauses
288 if nx_str_eq(op_buf, "and" as *u8) == 1 {
289 var done: nx_int = 0
290 while done == 0 {
291 nx_smt_skip_ws(p)
292 if p.pos[0] >= p.n { done = 1 }
293 if done == 0 {
294 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1; done = 1 }
295 if done == 0 {
296 let l: nx_int = nx_smt_parse_formula(p)
297 let unit: *nx_int = (sys_mmap(8)) as *nx_int
298 unit[0] = l
299 let _add: nx_int = nx_sat_add_clause(p.formula, unit, 1)
300 }
301 }
302 }
303 return
304 }
305
306 // (=> a b) -- (~a | b)
307 if nx_str_eq(op_buf, "=>" as *u8) == 1 {
308 let a: nx_int = nx_smt_parse_formula(p)
309 let b: nx_int = nx_smt_parse_formula(p)
310 nx_smt_skip_ws(p)
311 if p.pos[0] < p.n {
312 if p.buf[p.pos[0]] == 41 { p.pos[0] = p.pos[0] + 1 }
313 }
314 lits[0] = 0 - a
315 lits[1] = b
316 let _add: nx_int = nx_sat_add_clause(p.formula, lits, 2)
317 return
318 }
319}
320
321// Top-level: walk every command in the script. Returns *SatFormula.
322func nx_smtlib_parse(buf: *u8, n: nx_int) -> *SatFormula {
323 let p: *SmtParser = nx_smt_parser_new(buf, n)
324 let cmd_buf: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
325
326 var done: nx_int = 0
327 while done == 0 {
328 let t: nx_int = nx_smt_next_tok(p, cmd_buf)
329 if t == NX_SMT_TOK_EOF { done = 1 }
330 if t == NX_SMT_TOK_LPAREN {
331 // Read command name
332 let _t2: nx_int = nx_smt_next_tok(p, cmd_buf)
333 if nx_str_eq(cmd_buf, "set-logic" as *u8) == 1 {
334 // Skip the logic name + closing paren
335 let dummy: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
336 let _ld: nx_int = nx_smt_next_tok(p, dummy)
337 let _rp: nx_int = nx_smt_next_tok(p, dummy)
338 }
339 if nx_str_eq(cmd_buf, "declare-fun" as *u8) == 1 {
340 // (declare-fun name () Bool) -- skip everything to ')'
341 var depth: nx_int = 1
342 while depth > 0 {
343 let nt: nx_int = nx_smt_next_tok(p, cmd_buf)
344 if nt == NX_SMT_TOK_LPAREN { depth = depth + 1 }
345 if nt == NX_SMT_TOK_RPAREN { depth = depth - 1 }
346 if nt == NX_SMT_TOK_EOF { depth = 0 }
347 }
348 }
349 if nx_str_eq(cmd_buf, "declare-const" as *u8) == 1 {
350 let dummy: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
351 let _name: nx_int = nx_smt_next_tok(p, dummy)
352 let _sort: nx_int = nx_smt_next_tok(p, dummy)
353 let _name_id: nx_int = nx_smt_var_id(p, dummy)
354 let _rp: nx_int = nx_smt_next_tok(p, dummy)
355 }
356 if nx_str_eq(cmd_buf, "assert" as *u8) == 1 {
357 nx_smt_handle_assert(p)
358 // Eat the trailing ')'
359 let dummy: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
360 let _rp: nx_int = nx_smt_next_tok(p, dummy)
361 }
362 if nx_str_eq(cmd_buf, "check-sat" as *u8) == 1 {
363 let dummy: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
364 let _rp: nx_int = nx_smt_next_tok(p, dummy)
365 }
366 if nx_str_eq(cmd_buf, "exit" as *u8) == 1 {
367 let dummy: *u8 = sys_mmap(NX_SMT_MAX_SYM_LEN as i64)
368 let _rp: nx_int = nx_smt_next_tok(p, dummy)
369 done = 1
370 }
371 }
372 }
373 return p.formula
374}