Added unit tests and refactored setf

src/function/UserDefinedFunction.java

@@ -20,7 +20,7 @@ public class UserDefinedFunction extends LispFunction {
         this.name = name;
         this.body = body;
         this.lambdaExpression = new Cons(new Symbol(name), new Cons(lambdaList, body));
-        this.environment = SETF.getEnvironment();
+        this.environment = SETF.getSymbolTable();
 
         for (this.formalParameters = new ArrayList<>(); lambdaList.consp(); lambdaList = (Cons) lambdaList.getCdr())
             this.formalParameters.add(lambdaList.getCar().toString());
@@ -45,11 +45,11 @@ public class UserDefinedFunction extends LispFunction {
 
         // store the environment of the S-expression that called this function
         // (the current environment)
-        SymbolTable currentEnvironment = SETF.getEnvironment();
+        SymbolTable currentEnvironment = SETF.getSymbolTable();
 
         // replace the current environment with the environment of this
         // function
-        SETF.setEnvironment(environment);
+        SETF.setSymbolTable(environment);
 
         Cons currentSExpression = body;
         SExpression retval = null;
@@ -62,7 +62,7 @@ public class UserDefinedFunction extends LispFunction {
 
         // replace the environment of the S-expression that called this
         // function
-        SETF.setEnvironment(currentEnvironment);
+        SETF.setSymbolTable(currentEnvironment);
 
         // remove the bindings of the arguments to the formal parameter names
         // in the environment of this function

src/function/builtin/EVAL.java

@@ -48,7 +48,7 @@ public class EVAL extends LispFunction {
             return new Symbol(symbolName);
         }
 
-        return SETF.lookup(symbolName);
+        return SETF.lookupSymbolValue(symbolName);
     }
 
     public static boolean isDotted(Cons list) {

src/function/builtin/special/LET.java

@@ -18,13 +18,13 @@ public class LET extends LispFunction {
 
         // create a new symbol table on top of the current environment to add
         // all the local variables to
-        SymbolTable environment = new SymbolTable(SETF.getEnvironment());
+        SymbolTable environment = new SymbolTable(SETF.getSymbolTable());
 
         SExpression car = argList.getCar();
         Cons cdr = (Cons) argList.getCdr();
 
         addVariablesToTable(environment, car);
-        SETF.setEnvironment(environment);
+        SETF.setSymbolTable(environment);
 
         SExpression retval = Nil.getInstance();
 
@@ -35,7 +35,7 @@ public class LET extends LispFunction {
         }
 
         // restore the environment to its original value
-        SETF.setEnvironment(environment.getParent());
+        SETF.setSymbolTable(environment.getParent());
 
         return retval;
     }

src/function/builtin/special/SETF.java

@@ -1,108 +1,68 @@
 package function.builtin.special;
 
 import function.*;
-import function.builtin.*;
-import function.builtin.cons.LENGTH;
+import function.builtin.EVAL;
 import sexpression.*;
 import table.SymbolTable;
 
-/**
- * <code>SETF</code> represents the SETF form in Lisp.
- */
 public class SETF extends LispFunction {
 
-    private static SymbolTable environment = new SymbolTable();
+    private static SymbolTable symbolTable = new SymbolTable();
 
-    /**
-     * Look up the value of a symbol using its name.
-     *
-     * @param symbolName
-     *  the name of the symbol to look up
-     * @return
-     *  the value of <code>symbolName</code> if it has one; null otherwise
-     */
-    public static SExpression lookup(String symbolName) {
-        SymbolTable current = environment;
-
-        while (current != null) {
-            if (current.contains(symbolName)) {
-                return current.get(symbolName);
-            }
-
-            current = current.getParent();
-        }
+    public static SExpression lookupSymbolValue(String symbolName) {
+        for (SymbolTable t = symbolTable; t != null; t = t.getParent())
+            if (t.contains(symbolName))
+                return t.get(symbolName);
 
         return null;
     }
 
-    /**
-     * Set the current environment to the specified value.
-     *
-     * @param newEnvironment
-     *  the value to set the environment to
-     */
-    public static void setEnvironment(SymbolTable newEnvironment) {
-        environment = newEnvironment;
+    public static void setSymbolTable(SymbolTable newSymbolTable) {
+        symbolTable = newSymbolTable;
     }
 
-    /**
-     * Retrieve the current environment.
-     *
-     * @return
-     *  the current environment
-     */
-    public static SymbolTable getEnvironment() {
-        return environment;
+    public static SymbolTable getSymbolTable() {
+        return symbolTable;
     }
 
-    // The number of arguments that SETF takes.
-    private static final int NUM_ARGS = 2;
+    private ArgumentValidator argumentValidator;
 
-    public SExpression call(Cons argList) {
-        // retrieve the number of arguments passed to SETF
-        int argListLength = LENGTH.getLength(argList);
-
-        // make sure we have received the proper number of arguments
-        if (argListLength != NUM_ARGS) {
-            Cons originalSExpr = new Cons(new Symbol("SETF"), argList);
-            String errMsg = "too " +
-                            ((argListLength > NUM_ARGS) ? "many" : "few") +
-                            " arguments given to SETF: " + originalSExpr;
-
-            throw new RuntimeException(errMsg);
+    public SETF() {
+        this.argumentValidator = new ArgumentValidator("SETF");
+        this.argumentValidator.setExactNumberOfArguments(2);
+        this.argumentValidator.setFirstArgumentExpectedType(Symbol.class);
     }
 
-        SExpression symbol = argList.getCar();
+    public SExpression call(Cons argumentList) {
+        argumentValidator.validate(argumentList);
 
-        // make sure the first argument is a symbol
-        if (! symbol.symbolp()) {
-            throw new RuntimeException("SETF: " + symbol + " is not a symbol");
-        }
-
-        Cons cdr = (Cons) argList.getCdr();
+        Cons cdr = (Cons) argumentList.getCdr();
+        SExpression symbol = argumentList.getCar();
         SExpression value = EVAL.eval(cdr.getCar());
 
-        SymbolTable current = environment;
-
-        // set 'current' to the symbol table that contains 'symbol' or the
-        // global symbol table if 'symbol' is not in the environment
-        while ((! current.contains(symbol.toString())) &&
-               (current.getParent() != null)) {
-            current = current.getParent();
-        }
-
-        current.put(symbol.toString(), value);
+        SymbolTable table = findTableForSymbol(symbol);
+        table.put(symbol.toString(), value);
 
         return value;
     }
 
-    /**
-     * Determine if the arguments passed to this Lisp function should be
-     * evaluated.
-     *
-     * @return
-     *  <code>false</code>
-     */
+    private SymbolTable findTableForSymbol(SExpression symbol) {
+        SymbolTable table = symbolTable;
+
+        while (!isSymbolInTable(symbol, table) && !isGlobalTable(table))
+            table = table.getParent();
+
+        return table;
+    }
+
+    private boolean isSymbolInTable(SExpression symbol, SymbolTable table) {
+        return table.contains(symbol.toString());
+    }
+
+    private boolean isGlobalTable(SymbolTable table) {
+        return table.getParent() == null;
+    }
+
     public boolean evaluateArguments() {
         return false;
     }

test/function/builtin/special/SETFTester.java

@@ -0,0 +1,86 @@
+package function.builtin.special;
+
+import static org.junit.Assert.assertNull;
+import static testutil.TestUtilities.*;
+
+import org.junit.*;
+
+import function.ArgumentValidator.*;
+import function.builtin.EVAL.UndefinedSymbolException;
+import sexpression.LispNumber;
+import table.SymbolTable;
+
+public class SETFTester {
+
+    @Before
+    public void setUp() {
+        SETF.setSymbolTable(new SymbolTable());
+    }
+
+    @Test
+    public void testSetf() {
+        evaluateString("(setf a 23)");
+        assertSExpressionsMatch(evaluateString("23"), evaluateString("a"));
+    }
+
+    @Test
+    public void lookupDefinedSymbol() {
+        evaluateString("(setf a 23)");
+        assertSExpressionsMatch(evaluateString("23"), SETF.lookupSymbolValue("A"));
+    }
+
+    @Test
+    public void lookupUndefinedSymbol() {
+        assertNull(SETF.lookupSymbolValue("A"));
+    }
+
+    @Test
+    public void setfGlobalVariable() {
+        evaluateString("(setf a 23)");
+        SymbolTable global = SETF.getSymbolTable();
+        SETF.setSymbolTable(new SymbolTable(global));
+
+        evaluateString("(setf a 94)");
+        SETF.setSymbolTable(global);
+        assertSExpressionsMatch(evaluateString("94"), evaluateString("a"));
+    }
+
+    @Test(expected = UndefinedSymbolException.class)
+    public void setfLocalVariableDefined_DoesNotSetGlobal() {
+        SymbolTable global = SETF.getSymbolTable();
+        SymbolTable local = new SymbolTable(global);
+        local.put("A", new LispNumber("99"));
+        SETF.setSymbolTable(local);
+
+        evaluateString("(setf a 94)");
+        SETF.setSymbolTable(global);
+        evaluateString("a");
+    }
+
+    @Test
+    public void setfLocalVariableUndefined_SetsGlobal() {
+        SymbolTable global = SETF.getSymbolTable();
+        SymbolTable local = new SymbolTable(global);
+        SETF.setSymbolTable(local);
+
+        evaluateString("(setf a 94)");
+        SETF.setSymbolTable(global);
+        assertSExpressionsMatch(evaluateString("94"), evaluateString("a"));
+    }
+
+    @Test(expected = BadArgumentTypeException.class)
+    public void testSetfWithNonSymbol() {
+        evaluateString("(setf 1 2)");
+    }
+
+    @Test(expected = TooFewArgumentsException.class)
+    public void testSetfWithTooFewArguments() {
+        evaluateString("(setf x)");
+    }
+
+    @Test(expected = TooManyArgumentsException.class)
+    public void testSetfWithTooManyArguments() {
+        evaluateString("(setf a b c)");
+    }
+
+}