Re: Implementation Language Choice

Joachim Durchholz <joachim.durchholz@web.de> writes:


> Lex Spoon wrote:
>> The feature that is especially nice is the pattern-matching switch
>> statement that most functional languages include.
>
> Agreed, pattern matching is nice. ("Pattern matching" as in "use a
> typesafe union type, and recognize the variant at hand and disassemble
> the record elements, all in a single construct"; the pattern matching
> we're talking about here is unrelated to regular expressions or image
> processing.)
>
> Though it's beyond me why this never made it into mainstream imperative
> languages; it's exceedingly useful.


Most languages seem to allow defining new variants in different parts
of the code. For example, an OO language will let you make new
subclasses at other parts of the code. This makes it harder to define
and to compile (see, on topic!) the case construct.


Also, there is a downside in that you are decomposing the *concrete
represenation*. Many languages -- and especially OO languages --
treat this as a breach of encapsulation and try to prevent it.


-Lex

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