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When if is just a function

ryelang.org

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Re: When if is just a function

#51

Post by middayc »

hshdhdhehd wrote: post #49
hatthew wrote: post #14

This is interesting, but I'm not convinced it's better than the python it's being compared to. Memorizing and understanding the behavior of functions that perform control flow seems no easier than memorizing and understanding hardcoded syntax/keywords. The additional flexibility of making everything a first-class citizen allows people to write code that is too clever for its own good. I could be wrong but I think the…

I agree. In any somewhat functional language (I.e. all the mainstream ones) you can wrap "if" in a function if you please. E.g. function funif (b, f) { return (b && f()) } If you want to do clever stuff. I never feel the need as I would rather abstract over bigger things.

You can do it, but that is not how the (default) control structures work in those languages. There is usually also some syntax cost.

Re: When if is just a function

#52

Post by middayc »

bloaf wrote: post #40
kazinator wrote: post #28

Earlier quoted context omitted.

If you treat assignment as a function, then you have to reify environments as run-time objects, whereby you basically lose lexical scope. Lisp originally, as in LISP, had assignment as a function: it was called SET. To use it, you usually had to quote: (SET 'VAR 42). It worked without an environment parameter because variables were in a pervasive environment, but the quote was needed to get the variable symbol as a r…

So tcl handles it somewhat more elegantly, I think. It also has a set function, but does not require any special quoting because it uses the $ prefix to denote "get the value of this symbol": set a 5 puts $a #prints 5 and of course because it is modeled as a function (albeit an impure one) you can pass arguments to it as normal: set a b set $a 5 #equivalent to set b 5 puts $b #prints 5 of course, everything in tcl is…

I’ve personally always thought that REBOL’s use of set-words and similar constructs was a strength. It makes sense conceptually, is visually distinguishable, and maintains a strong sense of internal consistency.

REBOL (and by extension, Rye) was never designed around the idea that everything must be a function. It just turns out that this approach fits naturally within the core principles and rules of the language.

All “active” words happen to be functions, because nothing else is needed. The behavior of different word types (and, more broadly, value types) is determined by the evaluator. In that sense, you could say that Rye does have syntax, expressed through its distinct word types.

Re: When if is just a function

#54

Post by tromp »

For lambda calculus, the motto is "when everything is a function". The boolean true is the function λx.λy.x, while false is λx.λy.y. If b then x else y then simply becomes b x y. In a functional language like Haskell that is basically a typed lambda calculus with lots of syntactic sugar, we can replicate this with:

    type MyBool a = a -> a -> a

    myTrue :: MyBool a
    myTrue = \x y -> x
    myFalse :: MyBool a
    myFalse = \x y -> y

    myIf :: MyBool a -> a -> a -> a
    myIf b myThen myElse = b myThen myElse

    main = print $ myIf myTrue "true" "false"

Re: When if is just a function

#55

Post by middayc »

hatthew wrote: post #14

This is interesting, but I'm not convinced it's better than the python it's being compared to. Memorizing and understanding the behavior of functions that perform control flow seems no easier than memorizing and understanding hardcoded syntax/keywords. The additional flexibility of making everything a first-class citizen allows people to write code that is too clever for its own good. I could be wrong but I think the…

It depends on what you want. If you want the most stabile and predictable way to specify the behavior, then static control structures have little downsides.

If you want to explore with how you can specify behaviors or rules and create new options or the ones tightly fitting your problem domain or mental model, then this gives you more tools to do so.

Re: When if is just a function

#56

Post by danlitt »

ivanjermakov wrote: post #12

The drawback is that this approach elevates code blocks to first class. It means that there is a semantical difference between a value that is a block and a value that is a result of a block. This reduces code clarity, because now block def/result is discriminated by context instead of syntax. - closures get tricky, i.e. having outer scoped variables within a block - inter-block operators still need special care, e.g…

This criticism seems at face value to also apply to first-class functions, which I thought was a totally uncontroversial pattern. Do you dislike those too?

Re: When if is just a function

#58

Post by motorest »

I'm definitely missing some key insight because after reading the article I felt it was a strawman argument.

Python already has conditional expressions, which already allow 'x if (predicate) else y'. Therefore in Python if is already equivalent to a function, and is composable.

Once you realize this, and also understand that Python has logical operators that can short-circuit, all Python examples feel convoluted and required the blogger to go way out of it's way to write nonidiomatic Python. If the goal was to make a point with Python, why not write Python?

Re: When if is just a function

#59

Post by middayc »

motorest wrote: post #58

I'm definitely missing some key insight because after reading the article I felt it was a strawman argument. Python already has conditional expressions, which already allow 'x if (predicate) else y'. Therefore in Python if is already equivalent to a function, and is composable. Once you realize this, and also understand that Python has logical operators that can short-circuit, all Python examples feel convoluted and…

Python was used as an example because people know Python and reader can compare it to something known.

I wasn't trying to make Python look awkward. I was trying to write equivalent Python, you are very much welcome to suggest improvements to my Python examples.

Other languages could be used instead of Python, for example Javascript. But I feel Python is more contained language, with clear ways to do thing (I guess I don't know them that well :) )

Re: When if is just a function

#60

Post by ivanjermakov »

danlitt wrote: post #56
ivanjermakov wrote: post #12

The drawback is that this approach elevates code blocks to first class. It means that there is a semantical difference between a value that is a block and a value that is a result of a block. This reduces code clarity, because now block def/result is discriminated by context instead of syntax. - closures get tricky, i.e. having outer scoped variables within a block - inter-block operators still need special care, e.g…

This criticism seems at face value to also apply to first-class functions, which I thought was a totally uncontroversial pattern. Do you dislike those too?

First-class functions are problematic too[1], but function is always a definition. While code block is usually meant to be executed right away.

[1]: https://github.com/ziglang/zig/issues/1048

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