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digitalmars.D.learn - Calling Syntax (no, not UFCS)

reply "SirNickolas" <buknik95 yandex.ru> writes:
Hello! I'm new in D and it is amazing!

Can you tell me please if it is discouraged or deprecated to call 
a function by just putting its name, without brackets? It's quite 
unusual for me (used C++ and Python before), but I can see this 
practice even in the official Phobos documentation:

```
foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a"))
     ...
```

The code `.map!("a + a", "a * a")()` also compiles and works as 
expected, of course.
Aug 03 2015
next sibling parent "sigod" <sigod.mail gmail.com> writes:
On Monday, 3 August 2015 at 22:42:15 UTC, SirNickolas wrote:

 Hello! I'm new in D and it is amazing!

 Can you tell me please if it is discouraged or deprecated to 
 call a function by just putting its name, without brackets? 
 It's quite unusual for me (used C++ and Python before), but I 
 can see this practice even in the official Phobos documentation:

 ```
 foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a"))
     ...
 ```

 The code `.map!("a + a", "a * a")()` also compiles and works as 
 expected, of course.


http://dlang.org/function.html#optional-parenthesis

Also note http://dlang.org/function.html#property-functions
Aug 03 2015
prev sibling next sibling parent "John Colvin" <john.loughran.colvin gmail.com> writes:
On Monday, 3 August 2015 at 22:42:15 UTC, SirNickolas wrote:

 Hello! I'm new in D and it is amazing!

 Can you tell me please if it is discouraged or deprecated to 
 call a function by just putting its name, without brackets? 
 It's quite unusual for me (used C++ and Python before), but I 
 can see this practice even in the official Phobos documentation:

 ```
 foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a"))
     ...
 ```

 The code `.map!("a + a", "a * a")()` also compiles and works as 
 expected, of course.


Opinions are mixed, there is no clear consensus, it probably 
doesn't matter that much.

I try to make sure to put the parens in for a function that's 
really "doing" something, like modifying global state or doing 
non-trivial amounts of work, but apart from that I'm very 
inconsistent.
Aug 03 2015
prev sibling next sibling parent Justin Whear <justin economicmodeling.com> writes:
On Mon, 03 Aug 2015 22:42:14 +0000, SirNickolas wrote:


 Hello! I'm new in D and it is amazing!
 
 Can you tell me please if it is discouraged or deprecated to call a
 function by just putting its name, without brackets? It's quite unusual
 for me (used C++ and Python before), but I can see this practice even in
 the official Phobos documentation:
 
 ```
 foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a"))
      ...
 ```
 
 The code `.map!("a + a", "a * a")()` also compiles and works as
 expected, of course.


Opinions vary, but I think it's generally idiomatic to omit empty parens 
when chaining but otherwise include them.  E.g.:

void foo() { ... }

void main()
{
	foo;  // don't do this
	foo(); // do this

    // Empty parens in a chain are just noise:
	[1,2,3].map!(i => i + 1)()
	       .reduce!`a+b`()
		   .writeln();

    // This is better
	[1,2,3].map!(i => i + 1)
	       .reduce!`a+b`
		   .writeln();  // you may or may not want to conclude 
with parens
}

One gotcha that still gets me is with sort:

somearray.sort;  // calls the builtin property sort left over from D1, 
don't use!
somearray.sort();  // calls std.algorithm.sort with default `a<b` 
comparator

So:
somearray.map(i => i+1).array.sort().reduce!`a+b`.writeln();
Aug 03 2015
prev sibling parent "Gary Willoughby" <dev nomad.so> writes:
On Monday, 3 August 2015 at 22:42:15 UTC, SirNickolas wrote:

 Hello! I'm new in D and it is amazing!

 Can you tell me please if it is discouraged or deprecated to 
 call a function by just putting its name, without brackets? 
 It's quite unusual for me (used C++ and Python before), but I 
 can see this practice even in the official Phobos documentation:

 ```
 foreach (result; [ 1, 2, 3, 4 ].map!("a + a", "a * a"))
     ...
 ```

 The code `.map!("a + a", "a * a")()` also compiles and works as 
 expected, of course.


http://nomad.so/2013/08/alternative-function-syntax-in-d/
Aug 04 2015