Actually a GTD language means that the Happiness/Bread-and-Butter language is not powerful enough. If your Happiness/Bread-and-Butter language is powerful enough, and you really do use it whenever you can, then you should know how to either find all the libs that you need, or have hacked together the ones that you can't find.
Second, the Happiness language should be your Bread-and-Butter language. If you have a few years to work at learning a language really well, you should devote it to the most powerful language that exists. If you make your Bread-and-Butter language the most powerful language, and your Happiness language the same, you will have a very large programming lever and will be able to get the most done with the highest quality.
Second, the Happiness language should be your Bread-and-Butter language. If you have a few years to work at learning a language really well, you should devote it to the most powerful language that exists. If you make your Bread-and-Butter language the most powerful language, and your Happiness language the same, you will have a very large programming lever and will be able to get the most done with the highest quality.