5 ms·

> f x -- too mathematical! :) yet we are very happy to use the same syntax in shell scripts or the shell itself.

layer8 4y ago
I guess the difference is that nesting calls (commands) is much less common in the shell, and (closely related) commands don’t really have a return value.
- DougBTX 4y ago
  On the shell, it is all the other way around, so to use command substitution it is like this: f $(g x) To pass the output of g x to f.
- gpderetta 4y ago
  is it? In practice I find that my shell one liners are orders of magnitude more complex than what I would dare to write in any other 'proper' language: grep "hello ($(cat patterns.txt| tr '\n' '|'|grep ')$^)" <(ssh other.host "cat ~/file.txt") |tee >(grep 'a' >As.txt) >(grep 'b' > Bs.txt) [yes, gratuitous use of cat, sue me]
lyxsus 4y ago
We’re not, but your point is still valid.
georgyo 4y ago
I've heard this argument before, but this isn't true. In shell, f x y z, x y z are all augments to f. Doesn't matter if f takes one argument, all are passed to the function. With many functional languages this gets very confusing. IE what ie what does `f f x` do? In shell I know for sure. In the example f f x, it might be easy to parse. But in f x y z, any of x y z might be functions.
- nemaar 4y ago
  Most functional languages parse a b c d e f as a(b, c, d, e, f), it does not matter what b, c, d, e, f are. Do you know any language where this is different?
  - georgyo 4y ago
    I thought more languages did this but at least nix and ocaml do not actually behave like I thought. In Ruby however it is a bit more ugly def f x x + 1 end puts f f 1 > 3
    - the_af 4y ago
      I don't understand your objection, what output would you like to see instead?
      - lgessler 4y ago
        GP's point is that while yes, we know since `f` has arity 1 there's no ambiguity, in general you might not have the arity of any given function fresh in your head, and therefore can't tell (in Ruby) just from looking at `f f 1` whether it means a single invocation of an arity 2 function, or two invocations of an arity 1 function
        the_af 4y ago
        Ah! Right. It helps to have all functions be of arity 1 to disambiguate, yes.
  - dwenzek 4y ago
    OCaml and Haskell parse `a b c d e f` as `((((a b) c) d) e) f`.
    - jerf 4y ago
      And while different than Algol-descended languages, I don't think that's particularly confusing. (Not that you were saying so, just continuing the conversation.) You can put together a confusing expression with it, but I can put together confusing things with the Algol syntax with not too much effort too. I've got the source code with my name on the blame to prove it.
- zeckalpha 4y ago
  Many counter examples to this, xargs for one.
  - georgyo 4y ago
    xargs is not a counter example. It is not a shell builtin, it is a program that takes a bunch of string arguments like every other program a shell would call. xargs -0 -n1 bash -c 'mv $1 ${1//.js/.ts}' -- Everything to the right of xargs is a string argument passed to xargs.
    - zeckalpha 4y ago
      So an identifier representing a function? Isn’t that the same for most languages?
- momentoftop 4y ago
  It's pretty easy to reason about that particular example if you have a type system. In a simply typed language, "f f x" is just a type error, so it doesn't do anything. In the polymorphic lambda calculus, the typing will force f to either be the identity, meaning that "f f x = x", or it will be a constant function, so you just replace "f f" with the constant.

I guess the difference is that nesting calls (commands) is much less common in the shell, and (closely related) commands don’t really have a return value.

DougBTX 4y ago
On the shell, it is all the other way around, so to use command substitution it is like this: f $(g x) To pass the output of g x to f.
gpderetta 4y ago
is it? In practice I find that my shell one liners are orders of magnitude more complex than what I would dare to write in any other 'proper' language: grep "hello ($(cat patterns.txt| tr '\n' '|'|grep ')$^)" <(ssh other.host "cat ~/file.txt") |tee >(grep 'a' >As.txt) >(grep 'b' > Bs.txt) [yes, gratuitous use of cat, sue me]

lyxsus 4y ago

We’re not, but your point is still valid.

georgyo 4y ago

I've heard this argument before, but this isn't true. In shell, f x y z, x y z are all augments to f. Doesn't matter if f takes one argument, all are passed to the function. With many functional languages this gets very confusing. IE what ie what does `f f x` do? In shell I know for sure. In the example f f x, it might be easy to parse. But in f x y z, any of x y z might be functions.

nemaar 4y ago
Most functional languages parse a b c d e f as a(b, c, d, e, f), it does not matter what b, c, d, e, f are. Do you know any language where this is different?
- georgyo 4y ago
  I thought more languages did this but at least nix and ocaml do not actually behave like I thought. In Ruby however it is a bit more ugly def f x x + 1 end puts f f 1 > 3
  - the_af 4y ago
    I don't understand your objection, what output would you like to see instead?
    - lgessler 4y ago
      GP's point is that while yes, we know since `f` has arity 1 there's no ambiguity, in general you might not have the arity of any given function fresh in your head, and therefore can't tell (in Ruby) just from looking at `f f 1` whether it means a single invocation of an arity 2 function, or two invocations of an arity 1 function
      - the_af 4y ago
        Ah! Right. It helps to have all functions be of arity 1 to disambiguate, yes.
- dwenzek 4y ago
  OCaml and Haskell parse `a b c d e f` as `((((a b) c) d) e) f`.
  - jerf 4y ago
    And while different than Algol-descended languages, I don't think that's particularly confusing. (Not that you were saying so, just continuing the conversation.) You can put together a confusing expression with it, but I can put together confusing things with the Algol syntax with not too much effort too. I've got the source code with my name on the blame to prove it.
zeckalpha 4y ago
Many counter examples to this, xargs for one.
- georgyo 4y ago
  xargs is not a counter example. It is not a shell builtin, it is a program that takes a bunch of string arguments like every other program a shell would call. xargs -0 -n1 bash -c 'mv $1 ${1//.js/.ts}' -- Everything to the right of xargs is a string argument passed to xargs.
  - zeckalpha 4y ago
    So an identifier representing a function? Isn’t that the same for most languages?
momentoftop 4y ago
It's pretty easy to reason about that particular example if you have a type system. In a simply typed language, "f f x" is just a type error, so it doesn't do anything. In the polymorphic lambda calculus, the typing will force f to either be the identity, meaning that "f f x = x", or it will be a constant function, so you just replace "f f" with the constant.