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digitalmars.D.internals - [OT] What do you think about declaring functions with lambda syntax?

reply ddcovery <antoniocabreraperez gmail.com> writes:
Example:

import
   std.stdio,
   std.algorithm,
   std.array,
   std.conv
;

ulong factorial(ulong n) =>
   n>1 ? factorial(n-1)*n : 1
;

T[] sorted(T)(T[] xs) =>
   xs.length == 0 ? [] :
     xs[1..$].filter!(x=> x < xs[0]).array.sorted ~
     xs[0..1] ~
     xs[1..$].filter!(x=> x >= xs[0]).array.sorted
;

void main() =>
   [5,6,7,2,3].sorted.map!(i=>i.to!ulong.factorial).writeln
;
Dec 04 2020
next sibling parent ddcovery <antoniocabreraperez gmail.com> writes:
On Friday, 4 December 2020 at 11:12:23 UTC, ddcovery wrote:

 Example:
 ...


This is more functional :-)

import
   std.stdio,
   std.algorithm,
   std.array,
   std.conv
;

pure ulong factorial(ulong n) =>
   n>1 ? n * factorial(n-1) : 1
;

pure T[] sorted(T)(T[] xs) =>
   xs.length == 0 ? [] :
     xs[1..$].filter!(x=> x < xs[0]).array.sorted ~
     xs[0..1] ~
     xs[1..$].filter!(x=> x >= xs[0]).array.sorted
;

void main() =>
   [5,6,7,2,3].sorted.map!(i=>i.to!ulong.factorial).writeln
;
Dec 04 2020
prev sibling next sibling parent reply IGotD- <nise nise.com> writes:
On Friday, 4 December 2020 at 11:12:23 UTC, ddcovery wrote:

 Example:

 import
   std.stdio,
   std.algorithm,
   std.array,
   std.conv
 ;

 ulong factorial(ulong n) =>
   n>1 ? factorial(n-1)*n : 1
 ;

 T[] sorted(T)(T[] xs) =>
   xs.length == 0 ? [] :
     xs[1..$].filter!(x=> x < xs[0]).array.sorted ~
     xs[0..1] ~
     xs[1..$].filter!(x=> x >= xs[0]).array.sorted
 ;

 void main() =>
   [5,6,7,2,3].sorted.map!(i=>i.to!ulong.factorial).writeln
 ;


It is really ugly and doesn't help readability. It looks like 
another language.
Dec 04 2020
parent ddcovery <antoniocabreraperez gmail.com> writes:
On Saturday, 5 December 2020 at 00:55:23 UTC, IGotD- wrote:

 It is really ugly and doesn't help readability. It looks like 
 another language.


For me it is absolutely wonderful and totally readable 
(expressive)...  this is the way I like to write code when 
possible and this is, basically, D.

Yesterday, I found myself writing this:

ulong factorial(ulong n){return
   n>1 ? n*factorial(n-1) : 1
;}

Lambda notation is "syntax sugar" that compiler can transform to  
"{return ... }" transparently

You choose your favorite one for each situation (like f(x) or 
x.f() or x.f,  or like named parameters that will be introduced 
in future versions of D)

Dart already offers this capability.

// named function c like notation
int factorial(int n) { return ...; }
// named function lambda notation
int factorial(int n) => ...;
// Anonymous function c like notation
final int Function(int) f = (n){ return n*n; }
// Anonymous function lambda notation
final int Function(int n) f = (n) => n*n;

Scala does something similar (not really lambda notation, only 
the possibility to remove brackets because "return" is implicit)

def factorial(n:Int):Int = if (n>1) n * factorial(n-1) else 1;
def factorial(n:Int):Int = { if (n>1) n * factorial(n-1) else 1; }

In typescript and python you can assign a lambda to a variable 
and refer it from the body
// Typescript
const factorial = (n:bigint)=> n>1? n*factorial(n-1):1;
// Python
factorial = lambda n : factorial(n-1)*n if n>1 else 1;

This is not the est solution, but this is something (simple and 
effective)

As DConf2020 exposed  "D, the functional programming language 
nobody is talking about".  In my opinion, the possibility of 
functions without brackets/return would be a good reinforcement.
Dec 04 2020
prev sibling parent reply user1234 <user1234 12.de> writes:
On Friday, 4 December 2020 at 11:12:23 UTC, ddcovery wrote:

 Example:


There's a related proposal [1] and the NG discussion is there [2].

[1] https://github.com/dlang/dmd/pull/11833
[2] 
https://forum.dlang.org/post/cmgqwabzdqbtngmjidfw forum.dlang.org
Dec 04 2020
parent ddcovery <antoniocabreraperez gmail.com> writes:
On Saturday, 5 December 2020 at 03:06:02 UTC, user1234 wrote:

 On Friday, 4 December 2020 at 11:12:23 UTC, ddcovery wrote:

 Example:


 There's a related proposal [1] and the NG discussion is there 
 [2].

 [1] https://github.com/dlang/dmd/pull/11833


I love it!!!

Thanks
Dec 04 2020