Re: no empty (zero) string predicate in Elisp

["Pascal J. Bourguignon" <pjb@informatimago.com>]

Emanuel Berg <embe8573@student.uu.se> writes:

>> not higher-level either
>
> I don't know the scientific definition of "high-level"
> - or how it applies to these three Elisp functions.
>
> The reason I want a binary operator is that it is more
> intuitive: it refects my way of thinking - "is the
> string empty?" vs. "is the string equal to another
> string that is empty?" - also, because a binary
> operator reduces the number of data items in the code
> (with one, the empty string).

The only problem with that, is that a binary operator has 2 arguments:
    
    (binop a b)

therefore if you want a binary operator, you want:

    (string= s "")

On the other hand, if you want only one argument, then you want a unary
operator:

    (unary a)

and when this unary operator returns a boolean, you call it a predicate:

    (emptyp s)


> In general, I don't want the same function to be
> spelled out over and over to do the same thing -
> instead, I want it factored out, named, and invoked
> with a "minimal", that is, sufficient, interface.

Definitely.


-- 
__Pascal Bourguignon__                 http://www.informatimago.com/
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