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275 lines
11 KiB
Racket
275 lines
11 KiB
Racket
#lang racket/base
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(require racket/list
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racket/syntax
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brag/rules/stx-types
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syntax/id-table
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(prefix-in sat: "satisfaction.rkt")
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(for-template racket/base
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brag/codegen/runtime
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brag/private/internal-support))
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(provide (all-defined-out)
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(for-template (all-from-out brag/codegen/runtime
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brag/private/internal-support)))
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;; Given a flattened rule, returns a syntax for the code that
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;; preserves as much source location as possible.
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;;
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;; Each rule is defined to return a list with the following structure:
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;;
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;; stx :== (name (U tokens rule-stx) ...)
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;;
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(define (flat-rule->yacc-rule a-flat-rule)
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(syntax-case a-flat-rule ()
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[(rule-type origin name . clauses)
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(with-syntax ([translated-clauses (for/list ([clause-stx (in-list (syntax->list #'clauses))])
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(translate-clause clause-stx #'name #'origin))])
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#'[name . translated-clauses])]))
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;; translates a single primitive rule clause.
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;; A clause is a simple list of ids, lit, vals, and inferred-id elements.
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;; The action taken depends on the pattern type.
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(define (translate-clause a-clause rule-name/false origin)
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(define translated-patterns
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(let loop ([primitive-patterns (syntax->list a-clause)])
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(cond
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[(empty? primitive-patterns) null]
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[else
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(cons (syntax-case (first primitive-patterns) (id lit token inferred-id)
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[(id val)
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#'val]
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[(lit val)
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(datum->syntax #f (string->symbol (syntax-e #'val)) #'val)]
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[(token val)
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#'val]
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[(inferred-id val reason)
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#'val])
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(loop (rest primitive-patterns)))])))
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(define translated-actions
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(for/list ([translated-pattern (in-list translated-patterns)]
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[primitive-pattern (in-list (syntax->list a-clause))]
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[pos (in-naturals 1)])
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(if (eq? (syntax-property primitive-pattern 'hide) 'hide)
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#'null
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(with-syntax ([$X (format-id translated-pattern "$~a" pos)]
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[$X-start-pos (format-id translated-pattern "$~a-start-pos" pos)]
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[$X-end-pos (format-id translated-pattern "$~a-end-pos" pos)])
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(syntax-case primitive-pattern (id lit token inferred-id)
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;; When a rule usage is inferred, the value of $X is a syntax object
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;; whose head is the name of the inferred rule. We strip that out,
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;; leaving the residue to be absorbed.
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[(inferred-id val reason)
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#'(syntax-case $X ()
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[(inferred-rule-name . rest)
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(syntax->list #'rest)])]
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[(id val)
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;; at this point, the 'hide property is either #f or "splice"
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;; ('hide value is handled at the top of this conditional)
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;; we need to use boolean because a symbol is treated as an identifier.
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;; also we'll separate it into its own property for clarity and test for it in "runtime.rkt"
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#`(list (syntax-property $X 'splice-rh-id #,(and (syntax-property primitive-pattern 'hide) #t)))]
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[(lit val)
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#'(list (atomic-datum->syntax $X $X-start-pos $X-end-pos))]
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[(token val)
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#'(list (atomic-datum->syntax $X $X-start-pos $X-end-pos))])))))
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(define whole-rule-loc
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(if (empty? translated-patterns)
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#'(list (current-source) #f #f #f #f)
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(with-syntax ([$1-start-pos (datum->syntax (first translated-patterns) '$1-start-pos)]
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[$n-end-pos (format-id (last translated-patterns) "$~a-end-pos" (length translated-patterns))])
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#`(positions->srcloc $1-start-pos $n-end-pos))))
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;; move 'hide-or-splice-lhs-id property into function because name is datum-ized
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(with-syntax ([(translated-pattern ...) translated-patterns]
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[(translated-action ...) translated-actions])
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#`[(translated-pattern ...)
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(rule-components->syntax '#,rule-name/false translated-action ...
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#:srcloc #,whole-rule-loc
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#:hide-or-splice? #,(syntax-property rule-name/false 'hide-or-splice-lhs-id))]))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; collect-token-types: (listof rule-syntax) -> (values (listof identifier) (listof identifier))
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;;
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;; Given a rule, automatically derive the list of implicit and
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;; explicit token types we need to generate.
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;;
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;; Note: EOF is reserved, and will always be included in the list
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;; of explicit token types, though the user is not allow to express it themselves.
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(define (rules-collect-token-types rules)
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(define-values (implicit explicit)
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(for/fold ([implicit null]
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[explicit (list (datum->syntax (first rules) 'EOF))])
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([a-rule (in-list rules)])
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(syntax-case a-rule (rule)
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[(rule _ a-pattern)
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(let loop ([a-pattern #'a-pattern]
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[implicit implicit]
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[explicit explicit])
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(syntax-case a-pattern (id lit token choice repeat maybe seq EOF)
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[(id val)
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(values implicit explicit)]
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[(lit val)
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(values (cons #'val implicit) explicit)]
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[(token EOF)
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(raise-syntax-error #f "Token EOF is reserved and can not be used in a grammar" #'val)]
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[(token val)
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(values implicit (cons #'val explicit))]
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[(choice . vals)
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(for/fold ([implicit implicit]
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[explicit explicit])
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([v (in-list (syntax->list #'vals))])
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(loop v implicit explicit))]
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[(repeat min max val)
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(loop #'val implicit explicit)]
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[(maybe val)
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(loop #'val implicit explicit)]
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[(seq . vals)
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(for/fold ([implicit implicit]
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[explicit explicit])
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([v (in-list (syntax->list #'vals))])
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(loop v implicit explicit))]))])))
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(values (reverse implicit) (reverse explicit)))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; rule-id: rule -> identifier-stx
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;; Get the binding id of a rule.
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(define (rule-id a-rule)
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(syntax-case a-rule (rule)
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[(rule id a-pattern)
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#'id]))
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(define (rule-pattern a-rule)
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(syntax-case a-rule (rule)
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[(rule id a-pattern)
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#'a-pattern]))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; check-all-rules-defined!: (listof rule-stx) -> void
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(define (check-all-rules-defined! rules)
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(define table (make-free-id-table))
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;; Pass one: collect all the defined rule names.
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(for ([a-rule (in-list rules)])
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(free-id-table-set! table (rule-id a-rule) #t))
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;; Pass two: check each referenced id, and make sure it's been defined.
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(for* ([a-rule (in-list rules)]
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[referenced-id (in-list (rule-collect-used-ids a-rule))]
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#:unless (free-id-table-ref table referenced-id (λ () #f)))
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(raise-syntax-error #f (format "Rule ~a has no definition" (syntax-e referenced-id))
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referenced-id)))
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;; check-all-rules-no-duplicates!: (listof rule-stx) -> void
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(define (check-all-rules-no-duplicates! rules)
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(define table (make-free-id-table))
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;; Pass one: collect all the defined rule names.
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(for ([a-rule (in-list rules)])
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(define maybe-other-rule-id (free-id-table-ref table (rule-id a-rule) (λ () #f)))
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(when maybe-other-rule-id
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(raise-syntax-error #f (format "Rule ~a has a duplicate definition" (syntax-e (rule-id a-rule)))
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(rule-id a-rule)
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#f
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(list (rule-id a-rule) maybe-other-rule-id)))
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(free-id-table-set! table (rule-id a-rule) (rule-id a-rule))))
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;; rule-collect-used-ids: rule-stx -> (listof identifier)
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;; Given a rule, extracts a list of identifiers
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(define (rule-collect-used-ids a-rule)
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(syntax-case a-rule (rule)
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[(rule id a-pattern)
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(pattern-collect-used-ids #'a-pattern null)]))
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;; pattern-collect-used-ids: pattern-stx (listof identifier) -> (listof identifier)
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;; Returns a flat list of rule identifiers referenced in the pattern.
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(define (pattern-collect-used-ids a-pattern acc)
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(let loop ([a-pattern a-pattern]
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[acc acc])
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(syntax-case a-pattern (id lit token choice repeat maybe seq)
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[(id val)
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(cons #'val acc)]
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[(lit val)
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acc]
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[(token val)
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acc]
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[(choice . vals)
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(for/fold ([acc acc])
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([v (in-list (syntax->list #'vals))])
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(loop v acc))]
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[(repeat min max val)
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(loop #'val acc)]
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[(maybe val)
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(loop #'val acc)]
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[(seq . vals)
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(for/fold ([acc acc])
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([v (in-list (syntax->list #'vals))])
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(loop v acc))])))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;; check-all-rules-satisfiable: (listof rule-stx) -> void
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;; Does a simple graph traversal / topological sort-like thing to make sure that, for
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;; any rule, there's some finite sequence of tokens that
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;; satisfies it. If this is not the case, then something horrible
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;; has happened, and we need to tell the user about it.
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;;
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;; NOTE: Assumes all referenced rules have definitions.
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(define (check-all-rules-satisfiable! rules)
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(define toplevel-rule-table
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(make-free-id-table (for/list ([a-rule (in-list rules)])
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(cons (rule-id a-rule) (sat:make-and)))))
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(define leaves null)
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(define (make-leaf)
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(define a-leaf (sat:make-and))
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(set! leaves (cons a-leaf leaves))
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a-leaf)
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(define (process-pattern a-pattern)
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(syntax-case a-pattern (id lit token choice repeat maybe seq)
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[(id val)
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(free-id-table-ref toplevel-rule-table #'val)]
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[(lit val)
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(make-leaf)]
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[(token val)
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(make-leaf)]
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[(choice . vals)
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(let ([an-or-node (sat:make-or)])
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(for* ([v (in-list (syntax->list #'vals))]
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[a-child (in-value (process-pattern v))])
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(sat:add-child! an-or-node a-child))
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an-or-node)]
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[(repeat min max val)
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(syntax-case #'min ()
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[0 (make-leaf)]
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[_ (process-pattern #'val)])]
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[(maybe val) (make-leaf)]
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[(seq . vals)
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(let ([an-and-node (sat:make-and)])
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(for* ([v (in-list (syntax->list #'vals))]
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[a-child (in-value (process-pattern v))])
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(sat:add-child! an-and-node a-child))
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an-and-node)]))
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(for* ([a-rule (in-list rules)]
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[rule-node (in-value (free-id-table-ref toplevel-rule-table (rule-id a-rule)))])
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(sat:add-child! rule-node (process-pattern (rule-pattern a-rule))))
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(for-each sat:visit! leaves)
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(for* ([a-rule (in-list rules)]
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[rule-node (in-value (free-id-table-ref toplevel-rule-table (rule-id a-rule)))]
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#:unless (sat:node-yes? rule-node))
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(raise-syntax-error #f
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(format "Rule ~a has no finite derivation" (syntax-e (rule-id a-rule)))
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(rule-id a-rule)))) |