1 Embedded Parenlog
The easiest way to get started using Parenlog for Racket is with the main module:
| (require parenlog) | package: parenlog |
Here is a basic example of using Parenlog:
> (define-model family-tree (parent rogue moria) (parent rogue larn) (parent rogue omega) (parent rogue hack) (parent moria angband) (parent hack nethack) (parent angband tome) (parent angband zangband) (parent omega adom) (parent nethack adom) (parent nethack zapm) (parent nethack slashem) (parent nethack crawl) (:- (sibling X Y) (parent Z X) (parent Z Y) (,(compose not equal?) X Y)) (:- (adds? X Y Z) (,+ X Y :- Z)))
> (query-model family-tree (sibling adom zapm)) '(#hasheq())
> (query-model family-tree #:limit 4 (sibling X Y))
'(#hasheq((X . moria) (Y . larn))
#hasheq((X . moria) (Y . omega))
#hasheq((X . moria) (Y . hack))
#hasheq((X . larn) (Y . moria)))
> (query-model family-tree (adds? 5 6 Z)) eval:5:0: query-model: expected parenlog query s-expr or
expected the identifier `unsyntax'
at: 5
in: (query-model family-tree (adds? 5 6 Z))
parsing context:
while parsing parenlog query s-expr
term: (5 6 Z)
location: eval:5:0
while parsing parenlog query s-expr
term: (adds? 5 6 Z)
location: eval:5:0
while parsing parenlog query form
term: (adds? 5 6 Z)
location: eval:5:0
while parsing parenlog query
term: (adds? 5 6 Z)
location: eval:5:0
syntax
(define-model id (~seq #:require model-id) ... stmt ...)
stmt = head-query | (:- head-query body-query ...) head-query = s-expr body-query = s-expr | (== s-expr s-expr) | (,pred s-expr ...) | (,fun s-expr ... :- s-expr ...)
id : identifier?
pred : (any/c ... -> boolean?)
fun : (any/c ... -> any)
_ counts as variable that is unique at every occurrence.
A s-expr may contain unsyntax to escape to Racket.
syntax
syntax
(query-model model-expr maybe-limit body-query)
maybe-limit =
| #:limit limit-expr
model-expr : model?
limit-expr : number?
Returns a value matching the contract: (listof (hash/c symbol? anc/c)). Each value in this list is a substitution of body-query that model-expr proves.