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If only reality was based on timed competitions that 15-year-olds win. However, the problem that my colleague was solving was a lot more complicated than stack

by fogus 16y ago

If only reality was based on timed competitions that 15-year-olds win. However, the problem that my colleague was solving was a lot more complicated than stacking a bunch of static boxes in a idealized compartment. In fact, the type of "boxes" and the containment structures were not known at the time of the application development. Instead, he only knew that each could be described along various parameters. For example, there are these things called Foo and they can never be stacked on top of a Bar unless there was a Baz in between, but even then only if the transport was could support that load. These were very complex logistics rules. I suppose you could have written that all in a C loop, but you'd be toast when the new Quuxes were released and new ships were developed, or yada yada yada. As it turns out Prolog worked great. I guess programming an open-ended system would have taken the 15-year-olds an extra 6-7 minutes.

barrkel 16y ago
The more open-ended the clauses are, the more complex it gets, for sure, because you end up embedding a DSL to encode the rules (e.g. expression trees with a simple interpreter); and the more you push up that complexity, the more sense a niche solution like Prolog makes. What a lot of this ends up coming down to is the domain expertises of the code author. If you're uncomfortable with recursion, or writing simple interpreters, then Prolog is a much bigger win. Otherwise, it has a higher hurdle to climb. Interpreters themselves are pretty trivial. Writing a parser and interpreter for a simple expression language (no control flow or anything like that, just a predicate possibly with some arguments) should by itself take no more than an hour. I know from past experience it takes me about 25 minutes, as it's one of the first things I do when I learn a new language.

by fogus 16y ago

barrkel 16y ago

The more open-ended the clauses are, the more complex it gets, for sure, because you end up embedding a DSL to encode the rules (e.g. expression trees with a simple interpreter); and the more you push up that complexity, the more sense a niche solution like Prolog makes. What a lot of this ends up coming down to is the domain expertises of the code author. If you're uncomfortable with recursion, or writing simple interpreters, then Prolog is a much bigger win. Otherwise, it has a higher hurdle to climb. Interpreters themselves are pretty trivial. Writing a parser and interpreter for a simple expression language (no control flow or anything like that, just a predicate possibly with some arguments) should by itself take no more than an hour. I know from past experience it takes me about 25 minutes, as it's one of the first things I do when I learn a new language.