I usually write something I want to write which is not too big. If it is some code you want to see, you'll fight with the language. If it is just training code,

I usually write something I want to write which is not too big. If it is some code you want to see, you'll fight with the language. If it is just training code, you may give up (this is how I wrote my first Lisp raytracer, based on Paul Graham's one in ACL... sadly I lost the source for that and the newer one never got to translucency :/ )