public static string ToNormalForm(this ILambdaExpression lambdaExpression)
{
var normalFormVisitor = new NormalFormVisitor();
lambdaExpression.Accept(normalFormVisitor);
return(normalFormVisitor.Result);
}
public void GivenAProgramAndAParsedASTWeGetTheSameProgramFromTheAST()
{
var testLambda = "λs.(λz.(s z))";
var lambdaExpression = _parser.Parse(testLambda);
var printVisitor = new NormalFormVisitor();
lambdaExpression.Accept(printVisitor);
Assert.Equal("(λs.(λz.(s z)))", printVisitor.Result);
}
public void ApplicationTest()
{
var application = "λm.λn.λf.λx.m f (n f x)";
var lambdaExpression = _parser.Parse(application);
var printVisitor = new NormalFormVisitor();
lambdaExpression.Accept(printVisitor);
Assert.Equal("(λm.(λn.(λf.(λx.((m f) ((n f) x))))))", printVisitor.Result);
Assert.IsType <Abstraction>(lambdaExpression);
}
public void GivenBoundAndUnboundVariableWithTheSameName()
{
var application = "(λx.(λy.xy))x";
var lambdaExpression = _parser.Parse(application);
var interpreter = new InterpreterVisitor();
interpreter.Result.Accept(interpreter);
var printVisitor = new NormalFormVisitor();
lambdaExpression.Accept(printVisitor);
Assert.Equal("(λt.yt)", printVisitor.Result);
}
public void GivenTheIdentifyFunctionParseAndInterpretToTheIdentifyFunction()
{
var identityFunction = "λx.x";
var lambdaExpression = _parser.Parse(identityFunction);
var interpreter = new InterpreterVisitor();
lambdaExpression.Accept(interpreter);
var printVisitor = new NormalFormVisitor();
interpreter.Result.Accept(printVisitor);
Assert.Equal("(λx.x)", printVisitor.Result);
}
public void GivenAnApplicationEvaluateTheApplicationCorrectly()
{
var application = @"(λx.(λy.x)) (λx.(λy.x))";
var lambdaExpression = _parser.Parse(application);
var interpreter = new InterpreterVisitor();
var events = new ReductionEventCollector();
ConnectEvents(interpreter, events);
lambdaExpression.Accept(interpreter);
var printVisitor = new NormalFormVisitor();
interpreter.Result.Accept(printVisitor);
Assert.Collection(events.Events,
e => Assert.Equal("α", e),
e => Assert.Equal("β", e));
Assert.Equal("λy.(λx0.(λx1.x0))", printVisitor.Result);
}
