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That took me a bit to understand what is going on, but now that I see it it really is cool. Each line (e.g. [ 0 ], 1,) represents something similar to (ke

That took me a bit to understand what is going on, but now that I see it it really is cool. Each line (e.g. [ 0 ], 1,) represents something similar to (key,value) pairs. So, in the first example any input that matches the array ([0]) (or [1,293,592] for that matter) would return the "value", or in this case "1". It gets better with the following line, if the input matches a ([Number]) then it returns "function (n) { return n * factorial(n-1); }", a common recursive algorithm for finding a factorial. Really, a nice looking framework all around.

johnswamps 16y ago
Yep, it's pretty neat. If you're familiar with haskell (I'm not sure if haskell invented it, but it's probably the most well-known example) this will be familiar to you. For example, factorial could be written as: fac 0 = 1 fac n = n * fac(n-1)
- silentbicycle 16y ago
  Other languages with pattern matching include Prolog* , ML, and Erlang. (If I'm not mistaken, it originated with SNOBOL.) Awk also uses regular expression matching toward similar ends, but it's like comparing REs to a full parser. * Prolog has unification, actually, which is more powerful than pattern matching. Instead of trying to match a value against a list of patterns, it tries to match two (or more) potentially partially-defined values against each other. Pattern matching is one of my favorite language features. PM-based code is usually quite straightforward to read (especially compared to a jumble of nested 'if's!), and can be compiled to efficient decision trees. It also works well with both static typing (checking full coverage of ML-style variant types) and dynamic typing (such as with Erlang's receive). The closest thing most OO languages have is polymorphism, which tends to break up the pattern table into lots of little scattered ones (unless the language has multimethods), making it harder to see the big picture.

johnswamps 16y ago

Yep, it's pretty neat. If you're familiar with haskell (I'm not sure if haskell invented it, but it's probably the most well-known example) this will be familiar to you. For example, factorial could be written as: fac 0 = 1 fac n = n * fac(n-1)

silentbicycle 16y ago
Other languages with pattern matching include Prolog* , ML, and Erlang. (If I'm not mistaken, it originated with SNOBOL.) Awk also uses regular expression matching toward similar ends, but it's like comparing REs to a full parser. * Prolog has unification, actually, which is more powerful than pattern matching. Instead of trying to match a value against a list of patterns, it tries to match two (or more) potentially partially-defined values against each other. Pattern matching is one of my favorite language features. PM-based code is usually quite straightforward to read (especially compared to a jumble of nested 'if's!), and can be compiled to efficient decision trees. It also works well with both static typing (checking full coverage of ML-style variant types) and dynamic typing (such as with Erlang's receive). The closest thing most OO languages have is polymorphism, which tends to break up the pattern table into lots of little scattered ones (unless the language has multimethods), making it harder to see the big picture.