Add project files

.classpath

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+<?xml version="1.0" encoding="UTF-8"?>
+<classpath>
+	<classpathentry kind="src" output="target/classes" path="src/main/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="src/test/java">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.7">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="con" path="org.eclipse.m2e.MAVEN2_CLASSPATH_CONTAINER">
+		<attributes>
+			<attribute name="maven.pomderived" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" path="target/generated-sources/annotations">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="ignore_optional_problems" value="true"/>
+			<attribute name="m2e-apt" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="src" output="target/test-classes" path="target/generated-test-sources/test-annotations">
+		<attributes>
+			<attribute name="optional" value="true"/>
+			<attribute name="maven.pomderived" value="true"/>
+			<attribute name="ignore_optional_problems" value="true"/>
+			<attribute name="m2e-apt" value="true"/>
+			<attribute name="test" value="true"/>
+		</attributes>
+	</classpathentry>
+	<classpathentry kind="output" path="target/classes"/>
+</classpath>

.gitignore

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+.settings
+.vscode
+target/

.project

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+<?xml version="1.0" encoding="UTF-8"?>
+<projectDescription>
+	<name>universe</name>
+	<comment></comment>
+	<projects>
+	</projects>
+	<buildSpec>
+		<buildCommand>
+			<name>org.eclipse.jdt.core.javabuilder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+		<buildCommand>
+			<name>org.eclipse.m2e.core.maven2Builder</name>
+			<arguments>
+			</arguments>
+		</buildCommand>
+	</buildSpec>
+	<natures>
+		<nature>org.eclipse.jdt.core.javanature</nature>
+		<nature>org.eclipse.m2e.core.maven2Nature</nature>
+	</natures>
+</projectDescription>

README.MD

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+# Project Info
+A program that compiles (into MIPS Assembly) or interprets code written in a generic programming language.
+
+Written using Maven. A tester file can be located at `src/main/java/com/pilers/tester/Tester.java`.
+
+Steps:
+1. The preprocessor handles macros (i.e. #include) and pipes the input program as a stream of bytes to the scanner.
+2. Lexical analysis: the scanner scans the stream of bytes into a stream of tokens - entities that store their own type (Integer, String, or Boolean), value as a string, and line number. It transfers this stream of tokens to the parser.
+3. Syntax analysis: the parser parses the stream of tokens into an abstract syntax tree (AST). It passes this tree to an environment, which acts as a manager for variable and function values. The object nature of Environments allows the creation of sub-Environments, which allows the usage of local variables inside a function that don't affect variables of the same name outside of the function. Note that the parser returns a Program object which acts as the root node ofthe AST.
+4. If the program is set to interpret, see step 5. If the program is set to compile, see steps 6 and 7.
+5. The program is executed using an interpreter environment, which essentially acts as a map of variable values.
+6. The program is analyzed using a semantic analysis environment, which performs actions such as type checking, seeing if a variable exists when it is referenced, etc.
+7. The program is compiled into MIPS Assembly code using an Emitter in a specified filepath.

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.pilers.app</groupId>
+  <artifactId>universe</artifactId>
+  <version>1.0-SNAPSHOT</version>
+
+  <name>universe</name>
+  <!-- FIXME change it to the project's website -->
+  <url>http://www.example.com</url>
+
+  <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <maven.compiler.source>1.7</maven.compiler.source>
+    <maven.compiler.target>1.7</maven.compiler.target>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <version>4.11</version>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
+      <plugins>
+        <!-- clean lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#clean_Lifecycle -->
+        <plugin>
+          <artifactId>maven-clean-plugin</artifactId>
+          <version>3.1.0</version>
+        </plugin>
+        <!-- default lifecycle, jar packaging: see https://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_jar_packaging -->
+        <plugin>
+          <artifactId>maven-resources-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-compiler-plugin</artifactId>
+          <version>3.8.0</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-surefire-plugin</artifactId>
+          <version>2.22.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-jar-plugin</artifactId>
+          <version>3.0.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-install-plugin</artifactId>
+          <version>2.5.2</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-deploy-plugin</artifactId>
+          <version>2.8.2</version>
+        </plugin>
+        <!-- site lifecycle, see https://maven.apache.org/ref/current/maven-core/lifecycles.html#site_Lifecycle -->
+        <plugin>
+          <artifactId>maven-site-plugin</artifactId>
+          <version>3.7.1</version>
+        </plugin>
+        <plugin>
+          <artifactId>maven-project-info-reports-plugin</artifactId>
+          <version>3.0.0</version>
+        </plugin>
+      </plugins>
+    </pluginManagement>
+  </build>
+</project>

public/printHello.txt

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+writeln("Hello from the internet!");

src/main/java/com/pilers/ast/Assignment.java

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+package com.pilers.ast;
+
+import com.pilers.emitter.Emitter;
+import com.pilers.environment.*;
+import com.pilers.errors.ErrorString;
+import com.pilers.errors.InterpretException;
+import com.pilers.errors.CompileException;
+
+/**
+ * AST Assignment class
+ * Represents the assignment of a value to a variable
+ * 
+ * @author Gloria Zhu
+ */
+public class Assignment extends Statement
+{
+    private String var;
+    private Expression exp;
+
+    /**
+     * Constructs an Assignment object
+     * 
+     * @param var the name of the variable
+     * @param exp an expression for the value
+     * @throws TypeErrorException
+     */
+    public Assignment(String var, Expression exp)
+    {
+        this.var = var;
+        this.exp = exp;
+    }
+
+    /**
+     * Executes the assignment
+     * 
+     * @param env the execution environment (InterpreterEnvironment)
+     * @throws BreakException    if a break statement is executed
+     * @throws ContinueException if a continue statement is executed
+     * @throws InterpretException if there is a runtime error in assignment
+     *                          Happens if the varaible does not exist,
+     *                          or there is a type discrepancy between the
+     *                          variable and value
+     */
+    public void exec(InterpreterEnvironment env) 
+        throws BreakException, ContinueException, InterpretException
+    {
+        env.setVariable(var, exp.eval(env));
+    }
+
+    /**
+     * Semantic analysis for assignment
+     * Checks if the variable exists and the types are compatible
+     * 
+     * @throws CompileException if the conditions above are broken
+     * @param env the current environment
+     */
+    public void analyze(SemanticAnalysisEnvironment env) throws CompileException
+    {
+        exp.analyze(env);
+
+        String expectedType = env.getVariableType(var);
+
+        if (expectedType == null) throw new CompileException(ErrorString.unknownIdentifier(var));
+
+        if (!expectedType.equals(exp.type))
+            throw new CompileException(ErrorString.typeAssignment(expectedType, exp.type));
+    }
+
+    /**
+     * Compiles the assignment
+     * The specific depends on the type of the varaible
+     * 
+     * @param e the emitter
+     */
+    public void compile(Emitter e)
+    {
+        exp.compile(e); // most recent value is in v0
+
+        if (e.isGlobalVariable(var)) e.emit("sw $v0 "+"_data_"+var);
+        else
+        {
+            int index = e.getLocalVarIndex(var);
+            e.emit("sw $v0 " + index * 4 + "($sp)");
+        }
+
+    }
+
+}