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implementation module history
// $Id$
import spine
import rule
import graph
import pfun
import basic
from general import Optional,Yes,No
import StdEnv
// A history relates node-ids in the subject graph to patterns
:: History sym var
:== [HistoryAssociation sym var]
// An association between a node-id in the subject graph and a history pattern
:: HistoryAssociation sym var
:== ( var // Attachment point in the subject graph where the history pattern is "housed"
, HistoryPattern sym var // The pattern in the history
)
// A pattern in the history, specifying the most general subject graph (footprint) for a reduction sequence
:: HistoryPattern sym var
= Closed sym [HistoryPattern sym var] // Indicates a closed node-id in the subject graph (created by a (partial) match)
| OpenHist // Indicates an open node-id in the subject graph (created by instantiation)
| Extensible (Link var) // Indicates a link to an untouched node-id in the subject graph, where this pattern can be extended
// A link in a graph, indicated by its source node-id and the argument number
// The root of a graph can be indicated by the No constructor
:: Link var
:== Optional (var,Int)
/************************************************
* Verifying a subject graph against the history *
************************************************/
matchhistory
:: (History sym var) // Complete history against which to check
[var] // Node-ids for which to include history patterns
(Graph sym var) // Current subject graph
var // Current application point of strategy
-> [HistoryPattern sym var] // Matching history patterns
| == sym
& == var
matchhistory hist spinenodes sgraph snode
= foldr (checkassoc spinenodes sgraph snode) [] hist
checkassoc spinenodes sgraph snode (var,pat) rest
| isMember var spinenodes && checkpat sgraph pat snode
= [pat:rest]
= rest
checkpat :: (Graph sym var) (HistoryPattern sym var) var -> Bool | == sym & == var
checkpat sgraph (Closed psym pargs) snode
# (sdef,(ssym,sargs)) = varcontents sgraph snode
= sdef && psym==ssym && eqlen pargs sargs && and [checkpat sgraph parg sarg \\ parg<-pargs & sarg<-sargs]
checkpat sgraph OpenHist snode
= not (fst (varcontents sgraph snode))
checkpat _ (Extensible _) _
= True
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