1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
use crate::*;
use ast::{Expr, Join, Let, Stmt};
use hayami::{SymbolMap, SymbolTable};
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Builder<T = StandardCtx> {
symbols: SymbolTable<String, TableEntry, ahash::RandomState>,
vars: Vec<Option<TermId>>,
default_join_steps: u64,
ctx: T,
}
impl<T: Default + TyCtxMut> Default for Builder<T> {
fn default() -> Self {
Builder {
symbols: SymbolTable::default(),
vars: Vec::new(),
default_join_steps: 200,
ctx: T::default(),
}
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
struct TableEntry {
term: TermId,
level: u32,
}
impl TableEntry {
fn get(&self, level: u32, ctx: &mut (impl ConsCtx + ?Sized)) -> TermId {
let shift = level - self.level;
self.term.shifted(shift as i32, 0, ctx).unwrap()
}
}
impl<T, M> Builder<T>
where
T: TyCtxMut<TermEqCtx = M>,
M: TermEqCtxEdit,
{
#[inline]
pub fn new(ctx: T) -> Builder<T> {
Builder {
symbols: SymbolTable::default(),
vars: Vec::new(),
default_join_steps: 200,
ctx,
}
}
#[inline]
pub fn stmt(&mut self, stmt: &Stmt) -> Result<(), Error> {
match stmt {
Stmt::Let(stmt) => self.let_(stmt),
Stmt::Join(stmt) => self.join(stmt),
}
}
#[inline]
fn let_(&mut self, stmt: &Let) -> Result<(), Error> {
let value = if let Some(ty) = &stmt.ty {
self.expr_with(&stmt.value, ty)?
} else {
self.expr(&stmt.value)?
};
if let Some(ident) = &stmt.ident {
self.register_subst(ident.clone(), value);
}
Ok(())
}
#[inline]
fn join(&mut self, stmt: &Join) -> Result<(), Error> {
let source = self.expr(&stmt.source)?;
let target = stmt
.target
.as_deref()
.map(|target| self.expr(target))
.transpose()?;
if let Some(target) = &target {
match source.eq_in(target, self.ctx.eq_ctx()) {
Some(true) => return Ok(()),
Some(false) => return Err(Error::TermMismatch),
None if stmt.form == ast::Form::Null => return Err(Error::TermUnificationFailure),
None => {}
}
}
let max_steps = stmt.work_limit.unwrap_or(self.default_join_steps);
let cfg = NormalCfg {
max_steps,
eta: stmt.form.eta(),
head: stmt.form.head(),
sub: stmt.form.sub(),
};
let redex = source.reduce_until(cfg, target.clone(), &mut self.ctx)?;
if let Some(target) = &target {
if let Some(redex) = redex {
match redex.eq_in(target, self.ctx.eq_ctx()) {
Some(true) => {}
Some(false) => return Err(Error::TermMismatch),
None => return Err(Error::TermUnificationFailure),
}
self.ctx.eq_ctx().shallow_cons_make_term_eq(&source, &redex);
} else {
return Err(Error::TermUnificationFailure);
}
}
Ok(())
}
#[inline]
pub fn expr(&mut self, expr: &Expr) -> Result<TermId, Error> {
let result = match expr {
Expr::Ident(ident) => self.ident(&ident[..])?,
Expr::Var(ix) => self.var(*ix),
Expr::App(app) => self.app(app)?,
Expr::Lambda(lambda) => self.lambda(lambda)?.into_id_with(self.ctx.cons_ctx()),
Expr::Pi(pi) => self.pi(pi)?.into_id_with(self.ctx.cons_ctx()),
Expr::Universe(universe) => self.universe(*universe)?.into_id_with(self.ctx.cons_ctx()),
Expr::Enum(enum_) => self.enum_(enum_)?.into_id_with(self.ctx.cons_ctx()),
Expr::Variant(variant) => self.variant(variant)?.into_id_with(self.ctx.cons_ctx()),
Expr::Bool => self.get_bool().into_id_with(self.ctx.cons_ctx()),
Expr::Boolean(boolean) => self.boolean(*boolean).into_id_with(self.ctx.cons_ctx()),
Expr::Case(case) => self.case(case)?.into_id_with(self.ctx.cons_ctx()),
Expr::Annotated(annotated) => self.annotated(annotated)?,
Expr::Scope(scope) => self.scope(scope)?,
_ => return Err(Error::NotImplemented),
};
Ok(result)
}
#[inline]
pub fn get_var(&mut self, ix: u32) -> Option<Option<TermId>> {
if (ix as usize) < self.vars.len() {
let rev_ix = self.vars.len() - 1 - (ix as usize);
self.vars[rev_ix]
.shifted(
self.vars.len() as i32 - 1 - ix as i32,
0,
self.ctx.cons_ctx(),
)
.ok()
} else {
None
}
}
#[inline]
pub fn var(&mut self, ix: u32) -> TermId {
let ty = self.get_var(ix);
Var::new_unchecked(ix, ty.flatten()).into_id_with(self.ctx.cons_ctx())
}
#[inline]
pub fn ident(&mut self, ident: &str) -> Result<TermId, Error> {
if let Some(entry) = self.symbols.get(ident) {
let result = entry.get(self.vars.len() as u32, self.ctx.cons_ctx());
Ok(result)
} else {
Err(Error::UndefinedSymbol)
}
}
#[inline]
pub fn app(&mut self, app: &ast::App) -> Result<TermId, Error> {
self.app_slice(&app.0[..])
}
#[inline]
pub fn app_slice<E>(&mut self, slice: &[E]) -> Result<TermId, Error>
where
E: Borrow<Expr>,
{
let first = if let Some(first) = slice.get(0) {
self.expr(first.borrow())?
} else {
return Err(Error::NotImplemented);
};
self.apply_to_slice(first, &slice[1..])
}
#[inline]
pub fn apply_to_slice<E>(&mut self, func: TermId, slice: &[E]) -> Result<TermId, Error>
where
E: Borrow<Expr>,
{
let first = if let Some(first) = slice.get(0) {
self.expr(first.borrow())?
} else {
return Ok(func);
};
let app = self
.construct_app(func, first)?
.into_id_with(self.ctx.cons_ctx());
self.apply_to_slice(app, &slice[1..])
}
#[inline]
pub fn construct_app(&mut self, left: TermId, right: TermId) -> Result<App, Error> {
Ok(App::new_direct(left, right, None, &mut self.ctx))
}
#[inline]
pub fn lambda(&mut self, lambda: &ast::Lambda) -> Result<Lambda, Error> {
let param_ty = lambda
.param_ty
.as_ref()
.map(|param_ty| self.expr(param_ty))
.transpose()?;
let result = self.parametrized(
param_ty.as_ref(),
lambda.param_name.as_deref(),
&lambda.result,
)?;
Ok(Lambda::new_direct(param_ty, result, self.ctx.cons_ctx()))
}
#[inline]
pub fn pi(&mut self, pi: &ast::Pi) -> Result<Pi, Error> {
let param_ty = self.expr(&pi.param_ty)?;
let result = self.parametrized(
Some(¶m_ty),
pi.param_name.as_ref().map(Option::as_deref).flatten(),
&pi.result,
)?;
Ok(Pi::new(param_ty, result, self.ctx.cons_ctx()))
}
#[inline]
pub fn parametrized(
&mut self,
param_ty: Option<&TermId>,
param_name: Option<&str>,
result: &ast::Expr,
) -> Result<TermId, Error> {
self.vars.push(param_ty.cloned());
let nameframe = if let Some(name) = param_name {
let var = self.var(0);
self.symbols.push();
self.register_subst(name.to_string(), var);
true
} else {
false
};
let result = self.expr(result);
if nameframe {
self.symbols.pop();
}
self.vars.pop();
result
}
#[inline]
pub fn universe(&mut self, universe: ast::Universe) -> Result<Universe, Error> {
Universe::try_new(universe.level(), universe.is_var())
}
pub fn enum_(&mut self, enum_: &ast::Enum) -> Result<Enum, Error> {
let set = enum_.0.iter().cloned().collect();
Ok(Enum::new(set))
}
pub fn variant(&mut self, variant: &str) -> Result<Variant, Error> {
let ty = Enum::new(StringSet::singleton(variant)).into_id_with(self.ctx.cons_ctx());
Variant::new_direct(variant, ty)
}
#[inline]
pub fn get_bool(&mut self) -> Bool {
Bool::default()
}
#[inline]
pub fn boolean(&mut self, boolean: bool) -> Boolean {
Boolean::new_unchecked(boolean, None)
}
#[inline]
pub fn case(&mut self, case: &ast::Case) -> Result<Case, Error> {
if case.0.len() == 0 {
return Err(Error::NotImplemented);
}
let target_0 = self.expr(&case.0[0].pattern)?;
let matches = target_0
.ty()
.ok_or(Error::CannotInfer)?
.clone_into_id_with(self.ctx.cons_ctx());
let mut branches: SmallVec<[_; 16]> = case
.0
.iter()
.enumerate()
.map(|(i, branch)| {
let result = self.expr(&branch.result)?;
let tmp;
let target = if i == 0 {
&target_0
} else {
tmp = self.expr(&branch.pattern)?;
&tmp
};
let ix = Case::get_match(target, &matches)?.ok_or(Error::OutOfGas)?;
Ok((ix, result))
})
.collect::<Result<_, _>>()?;
branches.sort_by_key(|(ix, _)| *ix);
let len = branches.len();
branches.dedup_by_key(|(ix, _)| *ix);
if branches.len() < len {
warn!(
"{} shadowed branches in case statement",
len - branches.len()
)
}
let cases: SmallVec<[_; 32]> = branches.into_iter().map(|(_ix, b)| b).collect();
Case::new_minimal((&cases[..]).into(), matches, &mut self.ctx)
}
#[inline]
pub fn annotated(&mut self, annotated: &ast::Annotated) -> Result<TermId, Error> {
self.expr_with(&annotated.term, &annotated.ty)
}
#[inline]
pub fn expr_with(&mut self, expr: &Expr, annot: &Expr) -> Result<TermId, Error> {
let annot = self.expr(&annot)?;
let term = self.expr(&expr)?;
let coerced = term.coerce(Some(annot), &mut self.ctx)?.unwrap_or(term);
Ok(coerced)
}
#[inline]
pub fn scope(&mut self, scope: &ast::Scope) -> Result<TermId, Error> {
let mut errno = Ok(());
self.ctx.reset_unbound()?;
self.symbols.push();
for stmt in &scope.stmts {
if let Err(err) = self.stmt(stmt) {
errno = Err(err);
continue;
}
}
let result = match errno {
Ok(()) => self.expr(&scope.result),
Err(err) => Err(err),
};
self.symbols.pop();
result
}
#[inline]
pub fn register_subst(&mut self, symbol: String, subst: TermId) {
self.symbols.insert(
symbol,
TableEntry {
term: subst,
level: self.vars.len() as u32,
},
)
}
#[inline]
pub fn ctx(&mut self) -> &mut T {
&mut self.ctx
}
}
#[cfg(test)]
mod test {
use super::*;
#[test]
fn untyped_round_trip() {
let examples = [
"#true",
"#false",
"#bool",
"λx.x",
"(λx.x)(λx.x)",
"{
#let x = #true;
x
}",
"#enum { 'x 'y 'z }",
"#case { #true => #false; #false => #true }",
];
let ctx = StandardCtx::default();
let mut builder = Builder::new(ctx);
for example in examples {
let (rest, parsed) = isotope_parser::expr(example).unwrap();
assert_eq!(rest, "");
let built = builder.expr(&parsed).unwrap();
let ast = built.to_ast_in(&mut Untyped).unwrap();
let built_ast = builder.expr(&ast).unwrap();
assert_eq!(built.as_ptr(), built_ast.as_ptr());
}
}
#[test]
fn basic_head_reduction() {
let program = [
("#let i = λx:#bool.x;", true),
("#eq (i #true) => #true;", false),
("#eq (i #false) => #false;", false),
("#head (i #true) => #true;", true),
("#eq (i #true) => #true;", true),
("#eq (i #false) => #false;", false),
("#head (i #false) => #false;", true),
("#eq (i #true) => #true;", true),
("#eq (i #false) => #false;", true),
("#head #true => #false;", false),
("#head #true => #false;", false),
("#head (i #true) => #false;", false),
];
let ctx = StandardCtx::default();
let mut builder = Builder::new(ctx);
for (line, pass) in program {
let (rest, parsed) = isotope_parser::stmt(line).unwrap();
assert_eq!(rest, "");
let result = builder.stmt(&parsed);
if pass {
assert_eq!(result, Ok(()))
} else {
assert!(result.is_err())
}
}
}
}