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Comment by pansa2

7 days ago

> strange misuses of "call"

My favourite (least favourite?) is using “call” with “return”. On more than one occasion I’ve heard:

“When we call the return keyword, the function ends.”

35 comments

pansa2

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jamesfinlayson  6 days ago

I remember someone in university talking about the if function (which ostensibly takes one boolean argument).

  • Delphiza  6 days ago

    In Excel formulas everything is a function. IF, AND, OR, NOT are all functions. It is awkward and goes against what software devs are familiar with, but there are probably more people familiar with the Excel IF function than any other forms. Here is an example taken from the docs... =IF(AND(A3>B2,A3<C2),TRUE,FALSE)

  • weinzierl  6 days ago

    Sounds like something Prof. John Ousterhout would say:-; The place where this was literally accurate would be Tcl.

    I don't know enough Smalltalk to be sure but I think to remember it has a similar approach of everything is an object and I wouldn't be surprised if they'd coerced control flow somehow into this framework.

    Also Forth comes to mind, but that would probably be a stretch.

  • Zambyte  6 days ago

    If takes two or three arguments, but never one. The condition is the one made syntactically obvious in most languages, the consequent is another required argument, and the alternative is optional.

  • antonvs  6 days ago

    Try implementing that in most languages and you'll run into problems.

    In an imperative programming language with eager evaluation, i.e. where arguments are evaluated before applying the function, implementing `if` as a function will evaluate both the "then" and "else" alternatives, which will have undesirable behavior if the alternatives can have side effects.

    In a pure but still eager functional language this can work better, if it's not possible for the alternatives to have side effects. But it's still inefficient, because you're evaluating expressions whose result will be discarded, which is just wasted computation.

    In a lazy functional language, you can have a viable `if` function, because it will only evaluate the argument that's needed. But even in the lazy functional language Haskell, `if` is implemented as built-in syntax, for usability reasons - if the compiler understands what `if` means as opposed to treating it as an ordinary function, it can optimize better, produce better messages, etc.

    In a language with the right kind of macros, you can define `if` as a macro. Typically in that case, its arguments might be wrapped in lambdas, by the macro, to allow them to be evaluated only as needed. But Scheme and Lisp, which have the right kind of macros, don't define `if` as a macro for similar reasons to Haskell.

    One language in which `if` is a function is the pure lambda calculus, but no-one writes real code in that.

    The only "major" language I can think of in which `if` is actually a function (well, a couple of methods) is Smalltalk, and in that case it works because the arguments to it are code blocks, i.e. essentially lambdas.

    tl;dr: `if` as a function isn't practical in most languages.

    • immibis  6 days ago

      I don't think Haskell needs 'if' to be a construct for compiler optimization reasons; it could be implemented easily enough with pattern matching:

      if' :: Bool -> a -> a -> a

      if' True x _ = x

      if' False _ y = y

      The compiler could substitute this if it knew the first argument was a constant.

      Maybe it was needed in early versions. Or maybe they just didn't know they wouldn't need it yet. The early versions of Haskell had pretty terrible I/O, too.

      3 replies →

    • igouy  6 days ago

      Isn't practical in Smalltalk either, so the compiler does something special:

          ifFalse: alternativeBlock
        "Answer the value of alternativeBlock. Execution does not actually
         reach here because the expression is compiled in-line."

        ^alternativeBlock value

      1 reply →

  • ahartmetz  6 days ago

    I frequently see people treating if as if it was "taking a comparison", so: if (variable == true) ...

  • lmm  6 days ago

    if should be a function, though sadly many languages aren't good enough to express it and have to make it a builtin.

pwdisswordfishz  6 days ago

Eh, "return" is just a very restricted continuation with special syntax… it's a stretch to say you "call" it, but not unjustified.

layer8  6 days ago

Some people use parentheses for the return value, to make it look like a function call:

    return(value);

userbinator  6 days ago

I've heard that too --- the voice in my head automatically read it in the customary thick Indian accent.