jruby-mathlink

mathlink.rb

require 'java'
require 'JLink.jar'

# Java::ComWolframJlink::KernelLink
# http://reference.wolfram.com/mathematica/JLink/ref/java/com/wolfram/jlink/KernelLink.html
# http://reference.wolfram.com/mathematica/JLink/ref/java/com/wolfram/jlink/MathLink.html

# Java::ComWolframJlink::MathLinkException
# Java::ComWolframJlink::MathLinkFactory
# http://reference.wolfram.com/mathematica/JLink/ref/java/com/wolfram/jlink/MathLinkFactory.html

class Mathlink
  attr_accessor :timeout
  attr_reader :kernel_link
  attr_reader :debug

  @@math_kernel_path = [
      "/usr/local/bin/math",
      "/Applications/Mathematica.app/Contents/MacOS/MathKernel"
    ].find{ |f| File.exist?(f) }

  @@jlink_libdir = [
      "/usr/local/Wolfram/Mathematica/8.0/SystemFiles/Links/JLink",
      "/Applications/Mathematica.app/SystemFiles/Links/JLink"
    ].find{ |f| File.exist?(f) }

  def connect
    Java::JavaLang::System.setProperty("com.wolfram.jlink.libdir", @@jlink_libdir)
    @kernel_link = Java::ComWolframJlink::MathLinkFactory.createKernelLink(kernel_link_args)

    if @debug
      @kernel_link.addPacketListener(packet_printer)
    end

    @timeout ||= 5000
    @kernel_link.connect(@timeout)
    @kernel_link.discardAnswer
  end

  def disconnect
    @kernel_link.close if @kernel_link
  end

  def terminate
    @kernel_link.terminateKernel if @kernel_link
  end

  def eval(str)
    result = @kernel_link.evaluateToOutputForm(str,0)
    e = @kernel_link.getLastError
    raise e if e
    return result
  end

  def debug=(bool)
    @debug = bool

    if @kernel_link
      if @debug
        @kernel_link.addPacketListener(packet_printer)
      else
        @kernel_link.removePacketListener(packet_printer)
      end
    end
  end

  private

  def packet_printer
    @packet_printer ||= Java::ComWolframJlink::PacketPrinter.new(Java::JavaLang::System.out)
  end

  def kernel_link_args
    "-linkmode launch -linkname '#{@@math_kernel_path} -mathlink'"
  end

end

mathlink_spec.rb

require 'mathlink'

describe Mathlink do
  before do
    subject.debug = true if ENV["DEBUG"]
    subject.connect
  end

  after do
    subject.disconnect
  end

  it "does basic arithmatic" do
    subject.eval("2+2").should == "4"
  end

  it "can access the kernel link directly" do
    subject.kernel_link.evaluate("5+5")
    subject.kernel_link.waitForAnswer

    # TODO:
    # There are a set of int constants representing next data type coming through the link
    # This could be used to dynamically pull the next value of any type by mapping getter 
    # methods to int constants
    subject.kernel_link.getNext.should == 43

    subject.kernel_link.getInteger.should == 10
  end

  it "doesn't work after disconnect" do
    subject.disconnect
    expect { subject.eval("3+3") }.to raise_error Java::ComWolframJlink::MathLinkException
  end

  it "doesn't work after termination" do
    subject.terminate
    expect { subject.eval("3+3") }.to raise_error Java::ComWolframJlink::MathLinkException
  end

  it "does divide by zero" do
    subject.eval("5/0").should == "ComplexInfinity"
  end

  it "bubbles up thrown exceptions with evaluated code" do
    expect { subject.eval("Throw[\"Kamehameha!\"]") }.to raise_error Java::ComWolframJlink::MathLinkException
  end

  it "doesn't rethrow caught exceptions" do
    subject.eval( "Catch[a; b; Throw[c]; d; e]" ).should == 'c'
  end

  it "allows debugging to STDOUT" do
    pending "Would have to capture STDOUT in order to verify"
    subject.debug = true
  end

end