jruby

Added automatically generated method wrappers for calls into the GSL library using the object itself:

rgslffi GSL4r is a set of wrapper routines I'm creating around GNU Scientific Library (GSL) mathematical routines using the Foreign Function Interface (FFI) library for Ruby/JRuby. Using FFI helps avoid tying GSL only to the C based Ruby interpreters and potentially will make the library universally available across all Ruby implementations. Something we'd like to have while using JRuby for the ATA.

While working on rgslffiGSL4r, I needed to define a mapping for the gsl_complex struct (we'll ignore for now that gsl_complex is potentially platform dependent).

Here's my attempt:

  class GSL_Complex < ::FFI::Struct
    layout :dat, [:double, 2]

    R = 0
    I = 1

    def real()
      return self[:dat][R]
    end

    def imag()
      return self[:dat][I]
    end

    def equals( a )
      return ( a[:dat][R] == self[:dat][R] && a[:dat][I] == self[:dat][I] )
    end

    def set( r, i )
      self[:dat][R] = r
      self[:dat][I] = i
      return self
    end

    def set_real( r )
      self[:dat][R] = r
    end

    def set_imag( i )
      self[:dat][I] = i
    end

    def to_s()
      return "(#{self[:dat][R]},#{self[:dat][I]})"
    end
  end

I was stumped for a few hours on passing FFI::Structs into external routines, luckily, this post, 'Functions returning structures' (groups/google/ruby-ffi), tipped me off by showing how to return a struct by value:

From the C code:

...
    typedef struct
    { 
        int r, g, b, a; 
    } ALLEGRO_COLOR; 
...