Introduced global abstractions of input, output, and termination

src/environment/Environment.java

@@ -0,0 +1,56 @@
+package environment;
+
+import java.io.*;
+
+public class Environment {
+
+    private static final Environment instance = new Environment();
+
+    public static Environment getInstance() {
+        return instance;
+    }
+
+    private InputStream input;
+    private PrintStream output;
+    private PrintStream errorOutput;
+    private Runnable terminate;
+
+    private Environment() {}
+
+    public void setInput(InputStream input) {
+        this.input = input;
+    }
+
+    public void setOutput(PrintStream output) {
+        this.output = output;
+    }
+
+    public void setErrorOutput(PrintStream errorOutput) {
+        this.errorOutput = errorOutput;
+    }
+
+    public void setTerminate(Runnable terminate) {
+        this.terminate = terminate;
+    }
+
+    public InputStream getInput() {
+        return input;
+    }
+
+    public String getInputName() {
+        return input.toString();
+    }
+
+    public PrintStream getOutput() {
+        return output;
+    }
+
+    public PrintStream getErrorOutput() {
+        return errorOutput;
+    }
+
+    public void terminate() {
+        terminate.run();
+    }
+
+}

src/error/ErrorManager.java

@@ -1,7 +1,9 @@
 package error;
 
+import java.io.PrintStream;
 import java.text.MessageFormat;
-import java.util.function.Consumer;
+
+import environment.Environment;
 
 /**
  * Prints error messages and potentially terminates the application.
@@ -14,25 +16,28 @@ public class ErrorManager {
     private static final String ANSI_RED = "\u001B[31m";
     private static final String ANSI_PURPLE = "\u001B[35m";
 
-    private Runnable systemTerminatingFunction;
+    private Environment environment;
-    private Consumer<String> outputFunction;
 
-    public ErrorManager(Runnable systemTerminatingFunction, Consumer<String> outputFunction) {
+    public ErrorManager() {
-        this.systemTerminatingFunction = systemTerminatingFunction;
+        this.environment = Environment.getInstance();
-        this.outputFunction = outputFunction;
     }
 
     public void generateError(LispException lispException) {
-        outputFunction.accept(formatMessage(lispException));
+        printError(lispException);
 
         if (isCritical(lispException))
-            systemTerminatingFunction.run();
+            environment.terminate();
+    }
+
+    private void printError(LispException lispException) {
+        String formattedMessage = formatMessage(lispException);
+        environment.getErrorOutput().println(formattedMessage);
     }
 
     private String formatMessage(LispException lispException) {
         String color = isCritical(lispException) ? ANSI_PURPLE : ANSI_RED;
 
-        return MessageFormat.format("{0}error: {1}{2}\n", color, lispException.getMessage(), ANSI_RESET);
+        return MessageFormat.format("{0}error: {1}{2}", color, lispException.getMessage(), ANSI_RESET);
     }
 
     private boolean isCritical(LispException lispException) {

src/function/builtin/PRINT.java

@@ -1,35 +1,25 @@
 package function.builtin;
 
-import function.LispFunction;
+import environment.Environment;
-import function.builtin.cons.LENGTH;
+import function.*;
 import sexpression.*;
 
-/**
- * <code>PRINT</code> represents the PRINT function in Lisp.
- */
 public class PRINT extends LispFunction {
 
-    // The number of arguments that PRINT takes.
+    private ArgumentValidator argumentValidator;
-    private static final int NUM_ARGS = 1;
+    private Environment environment;
+
+    public PRINT() {
+        this.argumentValidator = new ArgumentValidator("PRINT");
+        this.argumentValidator.setExactNumberOfArguments(1);
+        this.environment = Environment.getInstance();
+    }
 
     public SExpression call(Cons argList) {
-        // retrieve the number of arguments passed to PRINT
+        SExpression argument = argList.getCar();
-        int argListLength = LENGTH.getLength(argList);
+        environment.getOutput().println(argument);
 
-        // make sure we have received the proper number of arguments
+        return argument;
-        if (argListLength != NUM_ARGS) {
-            Cons originalSExpr = new Cons(new Symbol("PRINT"), argList);
-            String errMsg = "too " + ((argListLength > NUM_ARGS) ? "many" : "few") + " arguments given to PRINT: "
-                            + originalSExpr;
-
-            throw new RuntimeException(errMsg);
-        }
-
-        SExpression arg = argList.getCar();
-
-        System.out.println(arg);
-
-        return arg;
     }
 
 }

src/interpreter/InteractiveLispInterpreter.java

@@ -1,36 +1,32 @@
 package interpreter;
 
-import java.io.*;
-
-import error.ErrorManager;
-
 public class InteractiveLispInterpreter extends LispInterpreter {
 
     private static final String GREETING = "SUNY Potsdam Lisp Interpreter - Version 4.4.3";
     private static final String PROMPT = "~ ";
 
-    public InteractiveLispInterpreter(InputStream inputStream, PrintStream outputStream, ErrorManager errorManager) {
+    @Override
-        super(inputStream, outputStream, errorManager);
-    }
-
     protected void printGreeting() {
-        outputStream.println(GREETING);
+        environment.getOutput().println(GREETING);
-        outputStream.println();
+        environment.getOutput().println();
     }
 
+    @Override
     protected void displayPrompt() {
-        outputStream.print(PROMPT);
+        environment.getOutput().print(PROMPT);
     }
 
+    @Override
     protected void erasePrompt() {
         for (int i = 0; i < PROMPT.length(); i++) {
-            outputStream.print("\b");
+            environment.getOutput().print("\b");
         }
     }
-    
+
+    @Override
     protected void printFarewell() {
-        outputStream.println();
+        environment.getOutput().println();
-        outputStream.println();
+        environment.getOutput().println();
     }
 
 }

src/interpreter/LispInterpreter.java

@@ -3,6 +3,7 @@ package interpreter;
 import java.io.*;
 import java.text.MessageFormat;
 
+import environment.Environment;
 import error.*;
 import function.builtin.EVAL;
 import parser.LispParser;
@@ -15,12 +16,25 @@ public class LispInterpreter {
 
     private LispParser parser;
     private ErrorManager errorManager;
-    protected PrintStream outputStream;
+    protected Environment environment;
 
-    public LispInterpreter(InputStream inputStream, PrintStream outputStream, ErrorManager errorManager) {
+    public LispInterpreter() {
-        this.errorManager = errorManager;
+        this.environment = Environment.getInstance();
-        this.parser = new LispParser(inputStream, inputStream.toString());
+        this.errorManager = new ErrorManager();
-        this.outputStream = outputStream;
+        this.parser = new LispParser(this.environment.getInput(), this.environment.getInputName());
+    }
+
+    public LispInterpreter(String fileName) {
+        this.environment = Environment.getInstance();
+        this.errorManager = new ErrorManager();
+
+        try {
+            this.environment.setInput(new FileInputStream(fileName));
+        } catch (FileNotFoundException e) {
+            this.errorManager.generateError(new LispFileNotFoundException(e));
+        }
+
+        this.parser = new LispParser(this.environment.getInput(), this.environment.getInputName());
     }
 
     public void interpret() {
@@ -53,7 +67,7 @@ public class LispInterpreter {
         String result = MessageFormat.format("{0}{1}{2}", ANSI_GREEN, EVAL.eval(sExpression), ANSI_RESET);
 
         erasePrompt();
-        outputStream.println(result);
+        environment.getOutput().println(result);
     }
 
     protected void erasePrompt() {}
@@ -71,7 +85,27 @@ public class LispInterpreter {
     }
 
     protected void printFarewell() {
-        outputStream.println();
+        environment.getOutput().println();
+    }
+
+    public static class LispFileNotFoundException extends LispException {
+
+        private static final long serialVersionUID = 1L;
+        private String message;
+
+        public LispFileNotFoundException(FileNotFoundException e) {
+            this.message = e.getMessage();
+        }
+
+        @Override
+        public int getSeverity() {
+            return ErrorManager.CRITICAL_LEVEL;
+        }
+
+        @Override
+        public String getMessage() {
+            return message;
+        }
     }
 
 }

src/interpreter/LispInterpreterBuilder.java

@@ -0,0 +1,19 @@
+package interpreter;
+
+import java.io.*;
+
+public interface LispInterpreterBuilder {
+
+    void setInput(InputStream inputStream);
+
+    void setOutput(PrintStream outputStream);
+
+    void setErrorOutput(PrintStream errorOutputStream);
+
+    void setTerminate(Runnable terminationFunction);
+
+    void useFile(String fileName);
+
+    LispInterpreter build();
+
+}

src/interpreter/LispInterpreterBuilderImpl.java

@@ -0,0 +1,54 @@
+package interpreter;
+
+import java.io.*;
+
+import environment.Environment;
+
+public class LispInterpreterBuilderImpl implements LispInterpreterBuilder {
+
+    private Environment environment;
+    private String fileName;
+    private boolean isInteractive;
+
+    public LispInterpreterBuilderImpl() {
+        this.environment = Environment.getInstance();
+        this.fileName = "";
+        this.isInteractive = true;
+    }
+
+    @Override
+    public void setInput(InputStream inputStream) {
+        this.environment.setInput(inputStream);
+    }
+
+    @Override
+    public void setOutput(PrintStream outputStream) {
+        this.environment.setOutput(outputStream);
+
+    }
+
+    @Override
+    public void setErrorOutput(PrintStream errorOutputStream) {
+        this.environment.setErrorOutput(errorOutputStream);
+    }
+
+    @Override
+    public void setTerminate(Runnable terminationFunction) {
+        this.environment.setTerminate(terminationFunction);
+    }
+
+    @Override
+    public void useFile(String fileName) {
+        this.fileName = fileName;
+        this.isInteractive = false;
+    }
+
+    @Override
+    public LispInterpreter build() {
+        if (isInteractive)
+            return new InteractiveLispInterpreter();
+        else
+            return new LispInterpreter(fileName);
+    }
+
+}

src/main/LispMain.java

@@ -1,8 +1,5 @@
 package main;
 
-import java.io.*;
-
-import error.*;
 import interpreter.*;
 
 public class LispMain {
@@ -10,41 +7,21 @@ public class LispMain {
     private LispMain() {}
 
     public static void main(String[] args) {
-        LispInterpreter interpreter = null;
+        LispInterpreter interpreter = buildInterpreter(args);
-        ErrorManager errorManager = new ErrorManager(() -> System.exit(1), System.err::print);
-
-        if (args.length > 0) {
-            String fileName = args[0];
-
-            try {
-                interpreter = new LispInterpreter(new FileInputStream(fileName), System.out, errorManager);
-            } catch (FileNotFoundException e) {
-                errorManager.generateError(new LispFileNotFoundException(e));
-            }
-        } else
-            interpreter = new InteractiveLispInterpreter(System.in, System.out, errorManager);
-
         interpreter.interpret();
     }
 
-    public static class LispFileNotFoundException extends LispException {
+    private static LispInterpreter buildInterpreter(String[] args) {
+        LispInterpreterBuilder builder = new LispInterpreterBuilderImpl();
+        builder.setInput(System.in);
+        builder.setOutput(System.out);
+        builder.setErrorOutput(System.err);
+        builder.setTerminate(() -> System.exit(1));
 
-        private static final long serialVersionUID = 1L;
+        if (args.length > 0)
-        private String message;
+            builder.useFile(args[0]);
 
-        public LispFileNotFoundException(FileNotFoundException e) {
+        return builder.build();
-            this.message = e.getMessage();
-        }
-
-        @Override
-        public int getSeverity() {
-            return ErrorManager.CRITICAL_LEVEL;
-        }
-
-        @Override
-        public String getMessage() {
-            return message;
-        }
     }
 
 }

test/error/ErrorManagerTester.java

@@ -1,13 +1,13 @@
 package error;
 
-import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.*;
-import static org.junit.Assert.assertTrue;
 
-import java.util.HashSet;
+import java.io.*;
-import java.util.Set;
+import java.util.*;
 
-import org.junit.Before;
+import org.junit.*;
-import org.junit.Test;
+
+import environment.Environment;
 
 public class ErrorManagerTester {
 
@@ -15,9 +15,13 @@ public class ErrorManagerTester {
     private static final String MESSAGE = "message";
 
     private Set<String> indicatorSet;
+    private ByteArrayOutputStream outputStream;
 
     private ErrorManager createErrorManagerWithIndicators() {
-        return new ErrorManager(() -> indicatorSet.add(TERMINATED), (String) -> indicatorSet.add(MESSAGE));
+        Environment.getInstance().setTerminate(() -> indicatorSet.add(TERMINATED));
+        Environment.getInstance().setErrorOutput(new PrintStream(outputStream));
+
+        return new ErrorManager();
     }
 
     private LispException createLispException(int severity) {
@@ -37,9 +41,26 @@ public class ErrorManagerTester {
         };
     }
 
+    private void assertTerminated() {
+        assertTrue(indicatorSet.contains(TERMINATED));
+    }
+
+    private void assertNotTerminated() {
+        assertFalse(indicatorSet.contains(TERMINATED));
+    }
+
+    private void assertErrorMessageNotWritten() {
+        assertTrue(outputStream.toByteArray().length == 0);
+    }
+
+    private void assertErrorMessageWritten() {
+        assertTrue(outputStream.toByteArray().length > 0);
+    }
+
     @Before
     public void setUp() {
         this.indicatorSet = new HashSet<>();
+        this.outputStream = new ByteArrayOutputStream();
     }
 
     @Test
@@ -47,7 +68,7 @@ public class ErrorManagerTester {
         ErrorManager errorManager = createErrorManagerWithIndicators();
 
         errorManager.generateError(createLispException(ErrorManager.CRITICAL_LEVEL));
-        assertTrue(indicatorSet.contains(TERMINATED));
+        assertTerminated();
     }
 
     @Test
@@ -55,15 +76,7 @@ public class ErrorManagerTester {
         ErrorManager errorManager = createErrorManagerWithIndicators();
 
         errorManager.generateError(createLispException(0));
-        assertFalse(indicatorSet.contains(TERMINATED));
+        assertNotTerminated();
-    }
-
-    @Test
-    public void noMessageDisplayedBeforeError() {
-        createErrorManagerWithIndicators();
-
-        assertFalse(indicatorSet.contains(TERMINATED));
-        assertFalse(indicatorSet.contains(MESSAGE));
     }
 
     @Test
@@ -71,8 +84,16 @@ public class ErrorManagerTester {
         ErrorManager errorManager = createErrorManagerWithIndicators();
 
         errorManager.generateError(createLispException(0));
-        assertFalse(indicatorSet.contains(TERMINATED));
+        assertNotTerminated();
-        assertTrue(indicatorSet.contains(MESSAGE));
+        assertErrorMessageWritten();
+    }
+
+    @Test
+    public void noMessageDisplayedBeforeError() {
+        createErrorManagerWithIndicators();
+
+        assertNotTerminated();
+        assertErrorMessageNotWritten();
     }
 
     @Test
@@ -80,8 +101,8 @@ public class ErrorManagerTester {
         ErrorManager errorManager = createErrorManagerWithIndicators();
 
         errorManager.generateError(createLispException(ErrorManager.CRITICAL_LEVEL));
-        assertTrue(indicatorSet.contains(TERMINATED));
+        assertTerminated();
-        assertTrue(indicatorSet.contains(MESSAGE));
+        assertErrorMessageWritten();
     }
 
 }