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Comment by msla | Hacker News Reader

> D also does not allow the syntax `a < b < c`. C does, to the eternal damnation of anyone who tries it.

Far be it for me to teach the Pope to pray, but would it be reasonably reasonable to make that do the right thing? If your compiler can disallow it, it can detect it, so the grammar is obviously thinkable, and the semantics might be as well.

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> would it be reasonably reasonable to make that do the right thing?

I did think about that, and it's a good question. I did not out of concern for some C code translated to D then mysteriously misbehaving.

In the syntax `a < b < c` both the `<` are different operators than the `<` in `a < b`. It is more similar to the ternary operator `a ? b : c`.

It could also just be a type error: `<` takes two integers and produces a boolean, so both `(a < b) < c` and `a < (b < c)` would be invalid.

I believe this is legal Python and does what you expect.

Most of the time it does what you expect. Sometimes it has its own pitfalls unfortunately. a in b == True is one weird example...

This is tricky, but it is at least a PEP 8 violation to compare a Boolean expression to True or False with ==, and a linter will complain. Programming in Python without a linter can be perilous in general.

I hate when people do that (in C++).

in lisp its (< a b c)

   The value of < is true if the numbers are in monotonically increasing order; otherwise it is false.

- clhs

The important thing is that it's unambiguous. One function is being called with three arguments. If you don't know what that function does, you look it up. No drama.

exactly. (< a b c) is much clearer than a < b < c

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