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definition module rule

// $Id$

from graph import Graph,Node
from StdOverloaded import ==,toString
from StdFile import <<<

// --- Exported types

:: Rule sym var
:: Rgraph sym var

// --- Functions on rules

// Build a rule from its constituents
mkrule :: [.var] .var (Graph .sym .var) -> Rule .sym .var

// The arguments of a rule, i.e. the roots of its lhs
arguments :: !.(Rule sym var) -> [var]

// The root of a rule, i.e. of its rhs
ruleroot :: !.(Rule sym var) -> var

// The graph part of a rule, i.e. its bindings
rulegraph :: !.(Rule sym var) -> Graph sym var

instance toString Rule sym var | toString sym & toString var & == var

// --- Functions on rooted graphs

// The empty rooted graph with a given root
emptyrgraph  :: .var -> Rgraph .sym .var

// Update the contents of a variable in a rooted graph
updatergraph :: var .(Node sym var) !.(Rgraph sym var) -> .Rgraph sym var

// Prune a rooted graph at a variable (making it free)
prunergraph  :: var !.(Rgraph sym var) -> .Rgraph sym var

// Get the root of a rooted graph
rgraphroot   :: !.(Rgraph sym var) -> var

// Get the graph part of a rooted graph
rgraphgraph  :: !.(Rgraph sym var) -> Graph sym var

// Build a rooted graph from a root and a graph
mkrgraph     :: .var (Graph .sym .var) -> Rgraph .sym .var

instance == (Rgraph sym var) | == sym & == var
instance toString (Rgraph sym var) | toString sym & toString var & == var
instance <<< Rgraph sym var | toString sym & toString var & == var
instance <<< Rule sym var | toString sym & toString,== var