wytp.types.extractors

Class TypeInvariantExtractor

java.lang.Object

wytp.types.extractors.TypeInvariantExtractor

All Implemented Interfaces:

TypeExtractor<Formula,WyalFile.Expr>

public class TypeInvariantExtractor
extends Object
implements TypeExtractor<Formula,WyalFile.Expr>

Responsible for extracting the invariant (if any) from a given type. For example, consider the following type declaration:

 type nat is (int x) where x >= 0
 

Then, extracting the invariant from type nat gives x >= 0. Likewise, extracting the invariant from the type bool|int gives the invariant (x is int) ==> (x >= 0). Finally, extracting the invariant from the type nat[] gives the invariant forall(int i).(0 <= i && i < |xs| ==> xs[i] >= 0).

Author:

David J. Pearce

Constructor Summary

Constructors

Constructor and Description
TypeInvariantExtractor(wybs.lang.NameResolver resolver)

Method Summary

Modifier and Type	Method and Description
Formula	extract(WyalFile.Type type, WyalFile.Expr root) Attempt to extract a certain kind of type from an arbitrary type.
Formula	extractTypeInvariantInner(WyalFile.Type type, WyalFile.Expr root, HashSet<WyalFile.Type> visited)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TypeInvariantExtractor

public TypeInvariantExtractor(wybs.lang.NameResolver resolver)

Method Detail

extract

public Formula extract(WyalFile.Type type,
                       WyalFile.Expr root)
                throws wybs.lang.NameResolver.ResolutionError

Description copied from interface: TypeExtractor

Attempt to extract a certain kind of type from an arbitrary type. This is necessary in the presence of powerful type connectives such as union, intersection and negation. For example, given the type {int x}|{int x} we can extract the type {int x}.

Specified by:

extract in interface TypeExtractor<Formula,WyalFile.Expr>

Parameters:

type - The type for which information is to be extracted

root - Supplementary information which may be used by the extractor.

Returns:

Throws:

wybs.lang.NameResolver.ResolutionError

extractTypeInvariantInner

public Formula extractTypeInvariantInner(WyalFile.Type type,
                                         WyalFile.Expr root,
                                         HashSet<WyalFile.Type> visited)
                                  throws wybs.lang.NameResolver.ResolutionError

Throws:

wybs.lang.NameResolver.ResolutionError