Why does `True == False is False` evaluate to False in Python? (2013)

Re:Why does `True == False is False` evaluate to False in Py... by bjoli on Saturday May 02, 2020 @10:18AM (#23051920)

All maths functions where it makes sense take arbitrarily many arguments. (+ 1 2 3) = 6. (< 1 2 3) = true. Everything in function position (directly after an opening paren) is either a function you want to apply or a macro you want to expand, except in a select few forms, such as binding forms and conditionals. The syntax of scheme is remarkably simple once you know the basics.

I have programmed python for about 20 years, and I still do stupid mistakes. I grooked all the r6rs scheme syntax in 20 minutes, except for (do ...) which somehow never sticks. It is also rarely used.

I have tried to evangelize scheme enough to know some people just don't like it, but for me it instantly clicked.

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Re:Why does `True == False is False` evaluate to False in Py... by edflsafoiewq on Saturday May 02, 2020 @05:35PM (#23055120)

+ and = are pretty obvious but it can still be confusing. Take not=. Does (not= x y z) mean adjacent numbers are disequal (x≠y≠z, by analogy to + and =)? Or that no two numbers are equal? Or that at least two numbers are disequal? Different lisps pick different meanings.

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Re:Why does `True == False is False` evaluate to False in Py... by bjoli on Sunday May 03, 2020 @09:53AM (#23058997)

Which lisps? I think I have only ever seen that in clojure (thinking it was a bad idea), and clojure seems scared of parentheses. (not (equal? x y z)) is clearer, but suffers from the same drawback as your question.

The problem I think is that not= returns true as long as any elements are non-equal, which means it is not analogous to +. I can't speak for clojure, but this is in line with all equality predicates in scheme, negated or not. A predicate that checked if any neighbours are not equal would in true scheme spirit probably be called not-any-neighbour-equal? :)

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