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Anonymous Mon 24 Feb 21:58:11 2020 No.11414595 View Reply Original Report

Quoted By:

Is there a notation system that is similar to Polish notation, but also works for superior-order functions (i.e.: that allows to express them without using parenthesis)?

Anonymous

Anonymous Mon 24 Feb 2020 22:04:37 No.11414609 Report

Quoted By: >>11414715 >>11414716

No.

Polish notation can work without parentheses, as long as there is a strict separation between terms and functions. As soon as your language allows you to pass functions themselves as arguments to other functions, then without parentheses there is no way to distinguish between a function used as a term and an invocation of a function.

Anonymous

Anonymous Mon 24 Feb 2020 22:51:12 No.11414715 Report

Quoted By:

>>11414609
I think it could be done, as long as all functions have fixed arity. You could introduce a function call operator, say $. All tokens would be interpreted as parameters to be passed to the currently pending operator, except for $ which would eat the next term, check its arity and open a new parameter-eating context.
It would be super ugly though.

Anonymous

Anonymous Mon 24 Feb 2020 22:51:38 No.11414716 Report

Quoted By:

>>11414609
What about this thing I came up with:
every term is coupled to an indicator of "priority" indicating which one should be applied first... example, the following expression:

A2 B3 C4 D1 E1 F3 G2 H1 I1 J1

means:

A2 B3 (C D)1 E1 F3 G2 H1 I1 J1

which means:

A2 (B (C D))1 E1 (F G)2 H1 I1 J1

which means:

(A (B (C D)))1 E1 ((F G) H)1 I1 J1

which means:

((A (B (C D))) (E (((F G) H) (I J))))

Anonymous

Anonymous Mon 24 Feb 2020 23:15:13 No.11414762 Report

Quoted By:

Correct me if I got wrong, but that's free when you have types. Haskell does this a lot.

flip :: (a->b->c)->b->a->c
mod :: a->a->a

So it is valid to call
flip mod 2 3

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