Is INTERPRETER an anti-pattern?
anti-patterns, design-patterns, greenspunning, interpreter-pattern, lisp
Solution
There's nothing in the interpreter pattern that says it has to be another programming language's syntax that you're interpreting. If you need to parse a simple mathematical expression, then interpreter is just the thing.
Knowing when to use a pattern is what prevents it from being an anti-pattern.
Problem
To me, the Interpreter patten sounds very much like an anti-pattern known as Greenspun's tenth rule: Any sufficiently complicated C or Fortran program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of Common Lisp. That is, if you need to use Interpreter, you're likely to create something that's slow, ad-hoc and poorly specified. The right solution is to use the right language from the beginning. Or, alternatively, embed a well known and well specified language into your application, such as Guile (the GNU embeddable scheme). Or use Haskell as an embedded domain-specific language. But I haven't seen this in practice--what are your experiences regarding building your own embedded languages? Is it a good idea? Is it better than embedding an already existing language? (I'm not particularly a lisp fanboy. It's nice, but so's C and Haskell and python and a lot of other languages.)