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Identity

Identity can be complicated; consider the humble tomato, which, in certain jurisdictions, has the honor of being both a fruit, according to Botany, and a vegetable, according to the Supreme Court of the United States of America. The court relied on the so-called ordinary meaning, presumably that a majority of the human population use the plant part as they do some plant parts, but not other plant parts. The no-so-humble tomato got drunk and set the hotel room on fire.

Need for closure is relevant here: a tomato is a vegetable, and that is that. Someone else: well, it depends...

On another continent, 白馬非馬 is a claim, which in longer form and in English runs along the lines of "supposing white horse is not horse". This is very relevant in programming, where 1 and 1.0 can be not equal, equal, automatically equal, or a type error. Arguments as to which behavior is correct can get pretty vigorous, and likely depends on the context. This may not be what someone with a high need for closure wants to hear.

    SBCL> (eq 1 0)

    NIL
    SBCL> (eq 1 1)

    T
    SBCL> (eq 1 1.0)

    NIL
    SBCL> (eql 1 1.0)

    NIL
    SBCL> (equal 1 1.0)

    NIL
    SBCL> (equalp 1 1.0)

    T
    SBCL> (= 1 1.0)

    T
    SBCL> (defun foo (x) (declare (integer x)) x)

    FOO
    SBCL> (foo 1.0)

    ERR #<TYPE-ERROR expected-type: INTEGER datum: 1.0>

The LISP aspect of this is probably better covered by Kent M. Pitman in "Parenthetically (The Best of Intentions // EQUAL Rights--and Wrongs--in Lisp)".

http://www.nhplace.com/kent/PS/EQUAL.html

You can probably tell it's an old link from the http.

Meanwhile, is tea a vegetable soup? Probably not; "tea" is not typically in the "soup" category, despite both usually being plant parts in typically hot water. Is tomato a tomato if you are in a food fight, are rather busy fending off thrown things, and are trying to find something to return the favors with? Maybe something forgot to identify something in all the fuss.

Video from a security camera clearly shows the defendant picking up and throwing a tomato; you might respond "I wasn't myself". In that case, what was your identity?

tags #lisp