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Truffle SL is an example language implemented using the Truffle API.
There is a newer version: 1.0.0-rc7
/*
 * Copyright (c) 2012, 2016, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * The Universal Permissive License (UPL), Version 1.0
 *
 * Subject to the condition set forth below, permission is hereby granted to any
 * person obtaining a copy of this software, associated documentation and/or
 * data (collectively the "Software"), free of charge and under any and all
 * copyright rights in the Software, and any and all patent rights owned or
 * freely licensable by each licensor hereunder covering either (i) the
 * unmodified Software as contributed to or provided by such licensor, or (ii)
 * the Larger Works (as defined below), to deal in both
 *
 * (a) the Software, and
 *
 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
 * one is included with the Software each a "Larger Work" to which the Software
 * is contributed by such licensors),
 *
 * without restriction, including without limitation the rights to copy, create
 * derivative works of, display, perform, and distribute the Software and make,
 * use, sell, offer for sale, import, export, have made, and have sold the
 * Software and the Larger Work(s), and to sublicense the foregoing rights on
 * either these or other terms.
 *
 * This license is subject to the following condition:
 *
 * The above copyright notice and either this complete permission notice or at a
 * minimum a reference to the UPL must be included in all copies or substantial
 * portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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package com.oracle.truffle.sl;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.math.BigInteger;

import com.oracle.truffle.api.Truffle;
import com.oracle.truffle.api.debug.DebuggerTags;
import com.oracle.truffle.api.dsl.UnsupportedSpecializationException;
import com.oracle.truffle.api.nodes.Node;
import com.oracle.truffle.api.nodes.NodeInfo;
import com.oracle.truffle.api.source.Source;
import com.oracle.truffle.api.source.SourceSection;
import com.oracle.truffle.api.vm.PolyglotEngine;
import com.oracle.truffle.api.vm.PolyglotEngine.Value;
import com.oracle.truffle.sl.builtins.SLDefineFunctionBuiltin;
import com.oracle.truffle.sl.builtins.SLNanoTimeBuiltin;
import com.oracle.truffle.sl.builtins.SLPrintlnBuiltin;
import com.oracle.truffle.sl.builtins.SLReadlnBuiltin;
import com.oracle.truffle.sl.nodes.SLTypes;
import com.oracle.truffle.sl.nodes.call.SLDispatchNode;
import com.oracle.truffle.sl.nodes.call.SLInvokeNode;
import com.oracle.truffle.sl.nodes.call.SLUndefinedFunctionException;
import com.oracle.truffle.sl.nodes.controlflow.SLBlockNode;
import com.oracle.truffle.sl.nodes.controlflow.SLBreakNode;
import com.oracle.truffle.sl.nodes.controlflow.SLContinueNode;
import com.oracle.truffle.sl.nodes.controlflow.SLDebuggerNode;
import com.oracle.truffle.sl.nodes.controlflow.SLIfNode;
import com.oracle.truffle.sl.nodes.controlflow.SLReturnNode;
import com.oracle.truffle.sl.nodes.controlflow.SLWhileNode;
import com.oracle.truffle.sl.nodes.expression.SLAddNode;
import com.oracle.truffle.sl.nodes.expression.SLBigIntegerLiteralNode;
import com.oracle.truffle.sl.nodes.expression.SLDivNode;
import com.oracle.truffle.sl.nodes.expression.SLEqualNode;
import com.oracle.truffle.sl.nodes.expression.SLFunctionLiteralNode;
import com.oracle.truffle.sl.nodes.expression.SLLessOrEqualNode;
import com.oracle.truffle.sl.nodes.expression.SLLessThanNode;
import com.oracle.truffle.sl.nodes.expression.SLLogicalAndNode;
import com.oracle.truffle.sl.nodes.expression.SLLogicalOrNode;
import com.oracle.truffle.sl.nodes.expression.SLMulNode;
import com.oracle.truffle.sl.nodes.expression.SLStringLiteralNode;
import com.oracle.truffle.sl.nodes.expression.SLSubNode;
import com.oracle.truffle.sl.nodes.local.SLReadLocalVariableNode;
import com.oracle.truffle.sl.nodes.local.SLWriteLocalVariableNode;
import com.oracle.truffle.sl.parser.Parser;
import com.oracle.truffle.sl.parser.SLNodeFactory;
import com.oracle.truffle.sl.parser.Scanner;
import com.oracle.truffle.sl.runtime.SLContext;
import com.oracle.truffle.sl.runtime.SLFunction;
import com.oracle.truffle.sl.runtime.SLFunctionRegistry;
import com.oracle.truffle.sl.runtime.SLNull;

/**
 * SL is a simple language to demonstrate and showcase features of Truffle. The implementation is as
 * simple and clean as possible in order to help understanding the ideas and concepts of Truffle.
 * The language has first class functions, but no object model.
 * 
 * SL is dynamically typed, i.e., there are no type names specified by the programmer. SL is
 * strongly typed, i.e., there is no automatic conversion between types. If an operation is not
 * available for the types encountered at run time, a type error is reported and execution is
 * stopped. For example, {@code 4 - "2"} results in a type error because subtraction is only defined
 * for numbers.
 *
 * 

 * Types:
 * 

 * Number: arbitrary precision integer numbers. The implementation uses the Java primitive type
 * {@code long} to represent numbers that fit into the 64 bit range, and {@link BigInteger} for
 * numbers that exceed the range. Using a primitive type such as {@code long} is crucial for
 * performance.
 * 
Boolean: implemented as the Java primitive type {@code boolean}.
 * 
String: implemented as the Java standard type {@link String}.
 * 
Function: implementation type {@link SLFunction}.
 * 
Null (with only one value {@code null}): implemented as the singleton
 * {@link SLNull#SINGLETON}.
 * 
 * The class {@link SLTypes} lists these types for the Truffle DSL, i.e., for type-specialized
 * operations that are specified using Truffle DSL annotations.
 *
 * 
 * Language concepts:
 * 

 * Literals for {@link SLBigIntegerLiteralNode numbers} , {@link SLStringLiteralNode strings},
 * and {@link SLFunctionLiteralNode functions}.
 * 
Basic arithmetic, logical, and comparison operations: {@link SLAddNode +}, {@link SLSubNode
 * -}, {@link SLMulNode *}, {@link SLDivNode /}, {@link SLLogicalAndNode logical and},
 * {@link SLLogicalOrNode logical or}, {@link SLEqualNode ==}, !=, {@link SLLessThanNode <},
 * {@link SLLessOrEqualNode ≤}, >, ≥.
 * 
Local variables: local variables must be defined (via a {@link SLWriteLocalVariableNode
 * write}) before they can be used (by a {@link SLReadLocalVariableNode read}). Local variables are
 * not visible outside of the block where they were first defined.
 * 
Basic control flow statements: {@link SLBlockNode blocks}, {@link SLIfNode if},
 * {@link SLWhileNode while} with {@link SLBreakNode break} and {@link SLContinueNode continue},
 * {@link SLReturnNode return}.
 * 
Debugging control: {@link SLDebuggerNode debugger} statement uses
 * {@link DebuggerTags#AlwaysHalt} tag to halt the execution when run under the debugger.
 * 
Function calls: {@link SLInvokeNode invocations} are efficiently implemented with
 * {@link SLDispatchNode polymorphic inline caches}.
 * 
 *
 * 
 * Syntax and parsing:

 * The syntax is described as an attributed grammar. The {@link Parser} and {@link Scanner} are
 * automatically generated by the parser generator Coco/R (available from
 * http://ssw.jku.at/coco/). The grammar contains semantic
 * actions that build the AST for a method. To keep these semantic actions short, they are mostly
 * calls to the {@link SLNodeFactory} that performs the actual node creation. All functions found in
 * the SL source are added to the {@link SLFunctionRegistry}, which is accessible from the
 * {@link SLContext}.
 *
 * 

 * Builtin functions:

 * Library functions that are available to every SL source without prior definition are called
 * builtin functions. They are added to the {@link SLFunctionRegistry} when the {@link SLContext} is
 * created. There current builtin functions are
 * 

 * {@link SLReadlnBuiltin readln}: Read a String from the {@link SLContext#getInput() standard
 * input}.
 * 
{@link SLPrintlnBuiltin println}: Write a value to the {@link SLContext#getOutput() standard
 * output}.
 * 
{@link SLNanoTimeBuiltin nanoTime}: Returns the value of a high-resolution time, in
 * nanoseconds.
 * 
{@link SLDefineFunctionBuiltin defineFunction}: Parses the functions provided as a String
 * argument and adds them to the function registry. Functions that are already defined are replaced
 * with the new version.
 * 
 */
public final class SLMain {

    /**
     * The main entry point. Use the mx command "mx sl" to run it with the correct class path setup.
     */
    public static void main(String[] args) throws IOException {
        Source source;
        if (args.length == 0) {
            source = Source.fromReader(new InputStreamReader(System.in), "").withMimeType(SLLanguage.MIME_TYPE);
        } else {
            source = Source.fromFileName(args[0]);
        }

        executeSource(source, System.in, System.out);
    }

    private static void executeSource(Source source, InputStream in, PrintStream out) throws IOException {
        out.println("== running on " + Truffle.getRuntime().getName());

        PolyglotEngine engine = PolyglotEngine.newBuilder().setIn(in).setOut(out).build();
        assert engine.getLanguages().containsKey(SLLanguage.MIME_TYPE);

        try {
            Value result = engine.eval(source);

            if (result == null) {
                throw new SLException("No function main() defined in SL source file.");
            } else if (result.get() != SLNull.SINGLETON) {
                out.println(result.get());
            }

        } catch (UnsupportedSpecializationException ex) {
            out.println(formatTypeError(ex));
        } catch (SLUndefinedFunctionException ex) {
            out.println(String.format("Undefined function: %s", ex.getFunctionName()));
        }

        engine.dispose();
    }

    /**
     * Provides a user-readable message for run-time type errors. SL is strongly typed, i.e., there
     * are no automatic type conversions of values. Therefore, Truffle does the type checking for
     * us: if no matching node specialization for the actual values is found, then we have a type
     * error. Specialized nodes use the {@link UnsupportedSpecializationException} to report that no
     * specialization was found. We therefore just have to convert the information encapsulated in
     * this exception in a user-readable form.
     */
    public static String formatTypeError(UnsupportedSpecializationException ex) {
        StringBuilder result = new StringBuilder();
        result.append("Type error");
        if (ex.getNode() != null && ex.getNode().getSourceSection() != null) {
            SourceSection ss = ex.getNode().getSourceSection();
            if (ss != null && ss.getSource() != null) {
                result.append(" at ").append(ss.getSource().getShortName()).append(" line ").append(ss.getStartLine()).append(" col ").append(ss.getStartColumn());
            }
        }
        result.append(": operation");
        if (ex.getNode() != null) {
            NodeInfo nodeInfo = SLContext.lookupNodeInfo(ex.getNode().getClass());
            if (nodeInfo != null) {
                result.append(" \"").append(nodeInfo.shortName()).append("\"");
            }
        }
        result.append(" not defined for");

        String sep = " ";
        for (int i = 0; i < ex.getSuppliedValues().length; i++) {
            Object value = ex.getSuppliedValues()[i];
            Node node = ex.getSuppliedNodes()[i];
            if (node != null) {
                result.append(sep);
                sep = ", ";

                if (value instanceof Long || value instanceof BigInteger) {
                    result.append("Number ").append(value);
                } else if (value instanceof Boolean) {
                    result.append("Boolean ").append(value);
                } else if (value instanceof String) {
                    result.append("String \"").append(value).append("\"");
                } else if (value instanceof SLFunction) {
                    result.append("Function ").append(value);
                } else if (value == SLNull.SINGLETON) {
                    result.append("NULL");
                } else if (value == null) {
                    // value is not evaluated because of short circuit evaluation
                    result.append("ANY");
                } else {
                    result.append(value);
                }
            }
        }
        return result.toString();
    }
}