Added unit tests and refactored lambda

design.txt

@@ -1,47 +0,0 @@
-Mike Cifelli
-CIS 443 - Programming Languages
-Lisp Interpreter Design Document
-
-    My implementation of LispScanner takes in an InputStream in its constructor
-that it will use to retrieve the Lisp tokens. It then creates a
-BufferedInputStream around this input stream so I can be sure that it will
-support the 'mark' and 'reset' methods (which the LispScanner requires to
-operate). A LispFilterStream is then created with this BufferedInputStream so I
-can retrieve all of the bytes from the original input stream without having to
-worry about dealing with Lisp comments.
-    When the LispScanner looks for the next Lisp token to return it uses a
-switch statement to determine the type of the next token (or to skip over
-whitespace). In the case of an identifier or number the scanner has to keep
-accumulating characters until it sees one that can not be a part of the number
-or identifier. Once one is found it has obviously been read from the input
-stream and this is not desirable as it is not part of the current token. This
-is where I made use of the 'mark' and 'reset' methods in the scanner. I mark
-the position before I read each character and when one is found that is not
-part of the current token I reset the input stream to its last position before
-the token is returned. This effectively unreads the last character so the input
-stream is in the proper position for the scanner's next read.
-
-    In the design of the LispParser I had some difficulty in implementing the
-'eof' method. This was due to the fact that in order to determine if a
-LispScanner was at the end of the input stream you have to read in a token.
-However, I did not want this method to read in a token since this would
-normally be part of an S-expression. Unfortunately, this meant that I would not
-be able to detect the end-of-file token until the 'getSExpr' method read it in.
-This is too late since the 'eof' method is used to determine when to stop
-calling the 'getSExpr' method.
-    My solution involved reading a token in the 'eof' method and then storing
-it in a variable. This would only be done once, until the token was used in the
-'getSExpr' method. I also stored any exceptions that were thrown during the
-read so that the 'eof' method would not give the impression of having read in
-any tokens. Any exception thrown in the 'eof' method during the retrieval of a
-token is stored and thrown the next time the 'getSExpr' method is called.
-
-    During the evaluation phase of the Lisp interpreter, I made use of the
-command pattern during function calls. By creating a LispFunction interface, I
-was able to place all of the built-in functions into a hash table mapping
-function names to the appropriate LispFunction. By looking up functions in this
-hash table, the proper function could be easily called during the evaluation of
-a list.
-
-    FINAL NOTE: The function table is located in the EVAL class and the symbol
-table is located in the SETF class.

src/function/ArgumentValidator.java

@@ -1,5 +1,6 @@
 package function;
 
+import java.math.BigInteger;
 import java.text.MessageFormat;
 
 import error.LispException;
@@ -11,8 +12,8 @@ public class ArgumentValidator {
     private Class<? extends SExpression> firstArgumentType;
     private Class<? extends SExpression> trailingArgumentType;
     private String functionName;
-    private Integer maximumNumberOfArguments;
+    private BigInteger maximumNumberOfArguments;
-    private Integer minimumNumberOfArguments;
+    private BigInteger minimumNumberOfArguments;
     private boolean isNilAcceptable;
 
     public ArgumentValidator(String functionName) {
@@ -38,16 +39,16 @@ public class ArgumentValidator {
     }
 
     public void setMaximumNumberOfArguments(int maximumNumberOfArguments) {
-        this.maximumNumberOfArguments = maximumNumberOfArguments;
+        this.maximumNumberOfArguments = BigInteger.valueOf(maximumNumberOfArguments);
     }
 
     public void setMinimumNumberOfArguments(int minimumNumberOfArguments) {
-        this.minimumNumberOfArguments = minimumNumberOfArguments;
+        this.minimumNumberOfArguments = BigInteger.valueOf(minimumNumberOfArguments);
     }
 
     public void setExactNumberOfArguments(int exactNumberOfArguments) {
-        this.minimumNumberOfArguments = exactNumberOfArguments;
+        this.minimumNumberOfArguments = BigInteger.valueOf(exactNumberOfArguments);
-        this.maximumNumberOfArguments = exactNumberOfArguments;
+        this.maximumNumberOfArguments = BigInteger.valueOf(exactNumberOfArguments);
     }
 
     public void doNotAcceptNil() {
@@ -78,11 +79,13 @@ public class ArgumentValidator {
     }
 
     private boolean containsTooFewArguments(Cons argumentList) {
-        return (minimumNumberOfArguments != null) && (LENGTH.getLength(argumentList) < minimumNumberOfArguments);
+        return (minimumNumberOfArguments != null)
+               && (LENGTH.getLength(argumentList).compareTo(minimumNumberOfArguments) < 0);
     }
 
     private boolean containsTooManyArguments(Cons argumentList) {
-        return (maximumNumberOfArguments != null) && (LENGTH.getLength(argumentList) > maximumNumberOfArguments);
+        return (maximumNumberOfArguments != null)
+               && (LENGTH.getLength(argumentList).compareTo(maximumNumberOfArguments) > 0);
     }
 
     private void validateArgumentTypes(Cons argumentList) {

src/function/builtin/EVAL.java

@@ -51,21 +51,6 @@ public class EVAL extends LispFunction {
         return SETF.lookupSymbolValue(symbolName);
     }
 
-    public static boolean isDotted(Cons list) {
-        if (list.nullp()) {
-            return false;
-        }
-
-        SExpression cdr = list.getCdr();
-
-        if (cdr.listp()) {
-            return isDotted((Cons) cdr);
-        }
-
-        // the cdr of 'list' is not a list, therefore it is dotted
-        return true;
-    }
-
     public static SExpression eval(SExpression sExpression) {
         Cons argumentList = LIST.makeList(sExpression);
         EVAL eval = new EVAL();

src/function/builtin/cons/LENGTH.java

@@ -7,12 +7,11 @@ import sexpression.*;
 
 public class LENGTH extends LispFunction {
 
-    public static int getLength(Cons list) {
+    public static BigInteger getLength(Cons list) {
         LENGTH lengthFunction = new LENGTH();
         LispNumber length = lengthFunction.callWithoutArgumentValidation(LIST.makeList(list));
 
-        return length.getValue().intValue(); // TODO - return BigInteger when all built-ins use
+        return length.getValue();
-                                             // ArgumentValidator
     }
 
     private ArgumentValidator argumentValidator;

src/function/builtin/special/LAMBDA.java

@@ -1,8 +1,7 @@
 package function.builtin.special;
 
 import function.*;
-import function.builtin.*;
+import function.builtin.cons.LIST;
-import function.builtin.cons.LENGTH;
 import sexpression.*;
 
 public class LAMBDA extends LispFunction {
@@ -17,52 +16,40 @@ public class LAMBDA extends LispFunction {
         return false;
     }
 
-    public static UserDefinedFunction createFunction(Cons lexpr) {
+    public static UserDefinedFunction createFunction(Cons lambdaExpression) {
-        LAMBDA lambda = new LAMBDA();
+        SExpression cdr = lambdaExpression.getCdr();
-        SExpression cdr = lexpr.getCdr();
 
-        // make sure lexpr is a proper list
+        ArgumentValidator lambdaValidator = new ArgumentValidator(":LAMBDA");
-        if (!cdr.consp()) {
+        lambdaValidator.setEveryArgumentExpectedType(Cons.class);
-            throw new RuntimeException("invalid lambda expression");
+        lambdaValidator.validate(LIST.makeList(cdr));
-        } else if (EVAL.isDotted((Cons) cdr)) {
-            throw new RuntimeException("dotted lambda expression " + lexpr);
-        }
 
-        Cons rest = (Cons) cdr;
+        LambdaExpression lambda = new LAMBDA().call((Cons) cdr);
 
-        return lambda.call(rest).getFunction();
+        return lambda.getFunction();
     }
 
-    // The minimum number of arguments that LAMBDA takes.
+    private ArgumentValidator argumentValidator;
-    private static final int MIN_ARGS = 2;
 
-    public LambdaExpression call(Cons argList) {
+    public LAMBDA() {
-        // retrieve the number of arguments passed to LAMBDA
+        this.argumentValidator = new ArgumentValidator("LAMBDA");
-        int argListLength = LENGTH.getLength(argList);
+        this.argumentValidator.setFirstArgumentExpectedType(Cons.class);
+        this.argumentValidator.setMinimumNumberOfArguments(2);
+    }
 
-        // make sure we have received the proper number of arguments
+    public LambdaExpression call(Cons argumentList) {
-        if (argListLength < MIN_ARGS) {
+        argumentValidator.validate(argumentList);
-            Cons originalSExpr = new Cons(new Symbol("LAMBDA"), argList);
-            String errMsg = "too few arguments given to LAMBDA: " + originalSExpr;
-
-            throw new RuntimeException(errMsg);
-        }
-
-        SExpression car = argList.getCar();
-
-        // make sure the list of arguments is a proper list
-        if (!car.listp()) {
-            throw new RuntimeException("LAMBDA: " + car + " is not a list");
-        } else if (EVAL.isDotted((Cons) car)) {
-            throw new RuntimeException("LAMBDA: " + car + " must be a proper list");
-        }
 
+        SExpression car = argumentList.getCar();
         Cons lambdaList = (Cons) car;
-        Cons body = (Cons) argList.getCdr();
+        Cons body = (Cons) argumentList.getCdr();
-        Cons lexpr = new Cons(new Symbol("LAMBDA"), argList);
+
         UserDefinedFunction function = new UserDefinedFunction(":LAMBDA", lambdaList, body);
 
-        return new LambdaExpression(lexpr, function);
+        return new LambdaExpression(makeOriginalLambdaExpression(argumentList), function);
+    }
+
+    private Cons makeOriginalLambdaExpression(Cons argumentList) {
+        return new Cons(new Symbol("LAMBDA"), argumentList);
     }
 
     public boolean evaluateArguments() {

test/function/builtin/special/LAMBDATester.java

@@ -0,0 +1,68 @@
+package function.builtin.special;
+
+import static org.junit.Assert.*;
+import static testutil.TestUtilities.*;
+
+import org.junit.Test;
+
+import function.ArgumentValidator.*;
+import sexpression.*;
+
+public class LAMBDATester {
+
+    @Test
+    public void testLambda() {
+        String input = "(lambda (x) x)";
+
+        assertSExpressionsMatch(parseString("(LAMBDA (X) X)"), evaluateString(input));
+    }
+
+    @Test
+    public void lambdaExpressionIsLambdaExpression() {
+        Cons lambdaExpression = new Cons(new Symbol("LAMBDA"),
+                                         new Cons(Nil.getInstance(), new Cons(Nil.getInstance(), Nil.getInstance())));
+
+        assertTrue(LAMBDA.isLambdaExpression(lambdaExpression));
+    }
+
+    @Test
+    public void somethingElseIsNotLambdaExpression() {
+        assertFalse(LAMBDA.isLambdaExpression(Symbol.T));
+    }
+
+    @Test
+    public void testCreateLambdaExpression() {
+        Cons lambdaExpression = new Cons(new Symbol("LAMBDA"),
+                                         new Cons(Nil.getInstance(), new Cons(Nil.getInstance(), Nil.getInstance())));
+
+        assertSExpressionsMatch(parseString("(:LAMBDA () ())"),
+                                LAMBDA.createFunction(lambdaExpression).getLambdaExpression());
+    }
+
+    @Test(expected = DottedArgumentListException.class)
+    public void testLambdaWithDottedArgumentList() {
+        String input = "(apply 'lambda (cons '(x) 1))";
+
+        evaluateString(input);
+    }
+
+    @Test(expected = DottedArgumentListException.class)
+    public void testCreateFunctionWithDottedArgumentList() {
+        Cons lambdaExpression = new Cons(new Symbol("LAMBDA"), new Cons(Nil.getInstance(), LispNumber.ONE));
+
+        LAMBDA.createFunction(lambdaExpression);
+    }
+
+    @Test(expected = BadArgumentTypeException.class)
+    public void testCreateFunctionWithNonList() {
+        Cons lambdaExpression = new Cons(new Symbol("LAMBDA"), LispNumber.ONE);
+
+        LAMBDA.createFunction(lambdaExpression);
+    }
+
+    @Test(expected = TooFewArgumentsException.class)
+    public void testLambdaWithTooFewArguments() {
+        evaluateString("(lambda ())");
+    }
+
+}