wyil.util.interpreter

Class Interpreter

java.lang.Object

wyil.util.interpreter.Interpreter

public class Interpreter
extends Object

A simple interpreter for WyIL bytecodes. The purpose of this interpreter is to provide a reference implementation for the semantics of WyIL bytecodes.

The interpreter is not intended to be time or space efficient. It also assume the underlying WyIL bytecodes are well formed and does not attempt to check them. Thus, malformed bytecodes can reuslt in the interpreter executing in an unpredictable fashion.

Author:

David J. Pearce

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Interpreter.ConstantLambda Represents an object allocated on the heap.
static class	Interpreter.ConstantObject Represents an object allocated on the heap.
static interface	Interpreter.InternalFunction An internal function is simply a named internal function.

Constructor Summary

Constructors

Constructor and Description
Interpreter(wybs.lang.Build.Project project, PrintStream debug)

Method Summary

Modifier and Type	Method and Description
void	checkInvariants(Constant[] frame, List<SyntaxTree.Location<Bytecode.Expr>> invariants) Evaluate zero or more conditional expressions, and check whether any is false.
void	checkInvariants(Constant[] frame, SyntaxTree.Location<Bytecode.Expr>... invariants) Evaluate zero or more conditional expressions, and check whether any is false.
static <T extends Constant> T	checkType(Constant operand, wybs.lang.SyntacticElement context, Class<T>... types) Check that a given operand value matches an expected type.
static Object	error(String msg, wybs.lang.SyntacticElement context) This method is provided as a generic mechanism for reporting runtime errors within the interpreter.
Constant[]	execute(wybs.lang.NameID nid, Type.FunctionOrMethod sig, Constant... args) Execute a function or method identified by a name and type signature with the given arguments, producing a return value or null (if none).
TypeSystem	getTypeSystem()
SyntaxTree.Location<Bytecode.VariableDeclaration>	getVariableDeclaration(SyntaxTree.Location<?> decl)
boolean	isMemberOfType(Constant value, Type type, wybs.lang.SyntacticElement context) Determine whether a given value is a member of a given type.

Methods inherited from class java.lang.Object

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

Constructor Detail

Interpreter

public Interpreter(wybs.lang.Build.Project project,
                   PrintStream debug)

Method Detail

getTypeSystem

public TypeSystem getTypeSystem()

execute

public Constant[] execute(wybs.lang.NameID nid,
                          Type.FunctionOrMethod sig,
                          Constant... args)

Execute a function or method identified by a name and type signature with the given arguments, producing a return value or null (if none). If the function or method cannot be found, or the number of arguments is incorrect then an exception is thrown.

Parameters:

nid - The fully qualified identifier of the function or method

sig - The exact type signature identifying the method.

args - The supplied arguments

Returns:

isMemberOfType

public boolean isMemberOfType(Constant value,
                              Type type,
                              wybs.lang.SyntacticElement context)
                       throws wybs.util.ResolveError

Determine whether a given value is a member of a given type. In the case of a nominal type, then we must also check that any invariant(s) for that type hold true as well.

Parameters:

value -

type -

context - --- Context in which bytecodes are executed

Returns:

Throws:

wybs.util.ResolveError - If a named type within the given type cannot be resolved within the enclosing project.

checkInvariants

public void checkInvariants(Constant[] frame,
                            List<SyntaxTree.Location<Bytecode.Expr>> invariants)

Evaluate zero or more conditional expressions, and check whether any is false. If so, raise an exception indicating a runtime fault.

Parameters:

frame -

context -

invariants -

checkInvariants

public void checkInvariants(Constant[] frame,
                            SyntaxTree.Location<Bytecode.Expr>... invariants)

Evaluate zero or more conditional expressions, and check whether any is false. If so, raise an exception indicating a runtime fault.

Parameters:

frame -

context -

invariants -

checkType

@SafeVarargs
public static <T extends Constant> T checkType(Constant operand,
                                                            wybs.lang.SyntacticElement context,
                                                            Class<T>... types)

Check that a given operand value matches an expected type.

Parameters:

operand - --- bytecode operand to be checked

context - --- Context in which bytecodes are executed

types - --- Types to be checked against

error

public static Object error(String msg,
                           wybs.lang.SyntacticElement context)

This method is provided as a generic mechanism for reporting runtime errors within the interpreter.

Parameters:

msg - --- Message to be printed when error arises.

context - --- Context in which bytecodes are executed

getVariableDeclaration

public SyntaxTree.Location<Bytecode.VariableDeclaration> getVariableDeclaration(SyntaxTree.Location<?> decl)