We just have a formal definition for + that we don't have right now. (As a side note, this is close to the actual implementation of the '+ defined in ac.scm). How can we know it works for strings, lists ? Does it works on chars or not ?
The goal is not to get rid of, say, -, * and / and implement them in Arc. Their signification is obvious and no one would need to see how they are implemented. This is not a math class. But this is not true of +, because by opening the black box it is, we have :
- the possibility for alternative implementations of the arc compiler, as most of the language is defined in itself. Imagine I want to work on a Forth implementation to put Arc code into fridges or TVs ; or pg thinks it's time to move on a C implementation to have a super-fast Arc. The smaller these axioms, the easier it is to get compatible compilers or to avoid bugs from one version to another.
- the possibility to say "I now want to use + for hash tables, let's add it, how is that implemented ?",
- the possibility to say "I don't need + to work for strings or chars or anything, I just want numeric addition because I'm crunching numbers ; +int is the function in need".
Incidentally, if I want to write +int, the only way to do so currently is to do (def +int a b (- a (- b))), and we both agree to say that it's a bad idea.
