What is Expressiveness in a Computer Language

[Pascal Costanza]

Marshall wrote:
> Anton van Straaten wrote:
>> But beyond that, there's an issue here about the definition of "the
>> language".  When programming in a latently-typed language, a lot of
>> action goes on outside the language - reasoning about static properties
>> of programs that are not captured by the semantics of the language.
>>
>> This means that there's a sense in which the language that the
>> programmer programs in is not the same language that has a formal
>> semantic definition.  As I mentioned in another post, programmers are
>> essentially mentally programming in a richer language - a language which
>> has informal (static) types - but the code they write down elides this
>> type information, or else puts it in comments.
>>
>> We have to accept, then, that the formal semantic definitions of
>> dynamically-checked languages are incomplete in some important ways.
>> Referring to those semantic definitions as "the language", as though
>> that's all there is to the language in a broader sense, is misleading.
>>
>> In this context, the term "latently-typed language" refers to the
>> language that a programmer experiences, not to the subset of that
>> language which is all that we're typically able to formally define.
> 
> That is starting to get a bit too mystical for my tastes.

To paraphrase Abelson & Sussman: Programs must be written for people to 
read, and only incidentally for compilers to check their types.

;)


Pascal

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