Indirect Left recursive grammars working
Chris Double
parent
68cbdf76aa
commit
dd979c8b3b
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@ -20,13 +20,18 @@ SYMBOL: packrat
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SYMBOL: pos
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SYMBOL: input
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SYMBOL: fail
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SYMBOL: lrstack
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SYMBOL: heads
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TUPLE: memo-entry ans pos ;
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C: <memo-entry> memo-entry
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TUPLE: left-recursion detected? ;
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TUPLE: left-recursion seed rule head next ;
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C: <left-recursion> left-recursion
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TUPLE: peg-head rule involved-set eval-set ;
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C: <head> peg-head
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: rule-parser ( rule -- parser )
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#! A rule is the parser compiled down to a word. It has
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#! a "peg" property containing the original parser.
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@ -72,6 +77,7 @@ C: <left-recursion> left-recursion
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:: (grow-lr) ( r p m h -- )
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p pos set
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h involved-set>> clone h (>>eval-set)
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r eval-rule
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dup fail = pos get m pos>> <= or [
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drop
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@ -82,39 +88,97 @@ C: <left-recursion> left-recursion
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] if ;
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:: grow-lr ( r p m h -- ast )
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#! Placeholder for full left recursion implementation
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r p m h (grow-lr) m pos>> pos set m ans>>
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h p heads get set-at
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r p m h (grow-lr)
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p heads get delete-at
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m pos>> pos set m ans>>
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;
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:: (setup-lr) ( r l s -- )
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s head>> l head>> eq? [
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l head>> s (>>head)
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l head>> [ s rule>> add ] change-involved-set drop
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r l s next>> (setup-lr)
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] unless ;
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:: setup-lr ( r l -- )
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l head>> [
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r V{ } clone V{ } clone <head> l (>>head)
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] unless
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r l lrstack get (setup-lr) ;
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:: lr-answer ( r p m -- ast )
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[let* |
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h [ m ans>> head>> ]
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h rule>> r eq? [
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m ans>> seed>> m (>>ans)
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m ans>> fail = [
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fail
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] [
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r p m h grow-lr
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] if
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] [
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m ans>> seed>>
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] if
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] ;
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:: recall ( r p -- memo-entry )
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[let* |
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m [ p r memo ]
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h [ p heads get at ]
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h [
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m r h involved-set>> h rule>> add member? not and [
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fail p <memo-entry>
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] [
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r h eval-set>> member? [
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h [ r swap remove ] change-eval-set drop
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r eval-rule
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m (>>ans)
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pos get m (>>pos)
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m
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] [
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m
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] if
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] if
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] [
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m
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] if
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] ;
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:: apply-non-memo-rule ( r p -- ast )
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[let* |
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lr [ f <left-recursion> ]
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m [ lr p <memo-entry> dup p r set-memo ]
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lr [ fail r f lrstack get <left-recursion> ]
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m [ lr lrstack set lr p <memo-entry> dup p r set-memo ]
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ans [ r eval-rule ]
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ans m (>>ans)
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lrstack get next>> lrstack set
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pos get m (>>pos)
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lr detected?>> ans fail = not and [
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r p m f grow-lr
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lr head>> [
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ans lr (>>seed)
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r p m lr-answer
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] [
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ans m (>>ans)
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ans
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] if
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] if
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] ;
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: apply-memo-rule ( m -- ast )
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[ ans>> ] [ pos>> ] bi
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pos set
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dup left-recursion? [
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t swap (>>detected?)
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fail
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] when ;
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:: apply-memo-rule ( r m -- ast )
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m pos>> pos set
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m ans>> left-recursion? [
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r m ans>> setup-lr
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m ans>> seed>>
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] [
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m ans>>
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] if ;
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:: apply-rule ( r p -- ast )
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[let* |
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m [ p r memo ]
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m [ r p recall ]
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m [
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m apply-memo-rule
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r m apply-memo-rule
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] [
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r p apply-non-memo-rule
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] if
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@ -125,6 +189,8 @@ C: <left-recursion> left-recursion
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swap [
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input set
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0 pos set
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f lrstack set
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H{ } clone heads set
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H{ } clone packrat set
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] H{ } make-assoc swap bind ;
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