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digitalmars.D.learn - Alternative to C++ macro in D

reply Vinod K Chandran <kcvinu82 gmail.com> writes:
Hi all,
I can do this in C++.
#include <iostream>
using namespace std ;

#define end };
#define log(x)  cout << x << endl
#define wait std::cin.get()


int main() {
     log("Trying to avoid the visual clutter aused by closing 
curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ;
     wait ;
end
How can i do this in D ? Especially the " #define end }; ". I've 
tried " alias end = } " but didn't worked.
Edit : How can add syntax highlighting and coloring in code 
posted on this comment ?
Nov 03 2019
next sibling parent reply Vinod K Chandran <kcvinu82 gmail.com> writes:
On Sunday, 3 November 2019 at 16:55:36 UTC, Vinod K Chandran 
wrote:

 Hi all,
 I can do this in C++.
 #include <iostream>
 using namespace std ;

 #define end };
 #define log(x)  cout << x << endl
 #define wait std::cin.get()


 int main() {
     log("Trying to avoid the visual clutter aused by closing 
 curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ;
     wait ;
 end
 How can i do this in D ? Especially the " #define end }; ". 
 I've tried " alias end = } " but didn't worked.
 Edit : How can add syntax highlighting and coloring in code 
 posted on this comment ?


How can i edit my post ? There is no button or link to edit my 
post.
Nov 03 2019
parent Alexandru Ermicioi <alexandru.ermicioi gmail.com> writes:
On Sunday, 3 November 2019 at 17:02:30 UTC, Vinod K Chandran 
wrote:

 On Sunday, 3 November 2019 at 16:55:36 UTC, Vinod K Chandran 
 wrote:

 Hi all,
 I can do this in C++.
 #include <iostream>
 using namespace std ;

 #define end };
 #define log(x)  cout << x << endl
 #define wait std::cin.get()


 int main() {
     log("Trying to avoid the visual clutter aused by closing 
 curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ;
     wait ;
 end
 How can i do this in D ? Especially the " #define end }; ". 
 I've tried " alias end = } " but didn't worked.
 Edit : How can add syntax highlighting and coloring in code 
 posted on this comment ?


 How can i edit my post ? There is no button or link to edit my 
 post.


You can't, web version is just a frontend for mailing list.

Best regards,
Alexandru.
Nov 03 2019
prev sibling next sibling parent Alexandru Ermicioi <alexandru.ermicioi gmail.com> writes:
On Sunday, 3 November 2019 at 16:55:36 UTC, Vinod K Chandran 
wrote:

 Hi all,
 I can do this in C++.
 #include <iostream>
 using namespace std ;

 #define end };
 #define log(x)  cout << x << endl
 #define wait std::cin.get()


 int main() {
     log("Trying to avoid the visual clutter aused by closing 
 curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ;
     wait ;
 end
 How can i do this in D ? Especially the " #define end }; ". 
 I've tried " alias end = } " but didn't worked.
 Edit : How can add syntax highlighting and coloring in code 
 posted on this comment ?


If this is about logging functionality, check 
std.experimental.log package, it contains all necessary logging 
functionality.

About macros there aren't any similar to preprocessor macros in 
c/c++, however you can replace them with three options depending 
on your needs:

1. Just a simple function in conjunction eith ctfe: 
https://tour.dlang.org/tour/en/gems/compile-time-function-evaluation-ctfe
2. string mixins: https://dlang.org/articles/mixin.html
3. template mixins: https://dlang.org/spec/template-mixin.html

I'd say number 2 should be suitable for your example given you'd 
like to inject statements into body of some function.

Best regards,
Alexandru.
Nov 03 2019
prev sibling next sibling parent Sebastiaan Koppe <mail skoppe.eu> writes:
On Sunday, 3 November 2019 at 16:55:36 UTC, Vinod K Chandran 
wrote:

 int main() {
     log("Trying to avoid the visual clutter aused by closing 
 curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ;
     wait ;
 end
 How can i do this in D ? Especially the " #define end }; ". 
 I've tried " alias end = } " but didn't worked.


You can't. D deliberately doesn't have a preprocessor. `#define 
end };` is one of the reasons.
Nov 03 2019
prev sibling next sibling parent Meta <jared771 gmail.com> writes:
On Sunday, 3 November 2019 at 16:55:36 UTC, Vinod K Chandran 
wrote:

 Hi all,
 I can do this in C++. #include <iostream>
 using namespace std ;

 #define end };
 #define log(x)  cout << x << endl
 #define wait std::cin.get()


 int main() {
     log("Trying to avoid the visual clutter aused by closing 
 curly braces") ;
     string myStr = "Now, code looks more elegant" ;
     log(myStr) ; mixin template cToD(string code)


`log` and `wait` are straightforward. Just write a function:

import std.stdio;
void log(T)(T x) { writeln(x); }
void wait() { readln(); }

However, you can't do things like `#define end }`. The D language 
intentionally disallows doing stuff like this. If you *really* 
want to do this, you can sort of emulate it with mixins:

mixin template cToD(string code)
{
     import std.array: replace;
     mixin(code.replace("end", "}"));
}

mixin cToD!`
     int main() {
         log("Trying to avoid the visual clutter aused by closing 
curly braces") ;
         string myStr = "Now, code looks more elegant" ;
         log(myStr) ;
         wait ;
         return 0;
     end
`;

But I would strongly recommend against it.
Nov 03 2019
prev sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 11/03/2019 08:55 AM, Vinod K Chandran wrote:

 Hi all,
 I can do this in C++.
 #include <iostream>
 using namespace std ;

 #define end };
 #define log(x)  cout << x << endl
 #define wait std::cin.get()


There is nothing that stops one from using the C++ preprocessor on any 
text file. For example, you can do the following wherever GCC exists. If 
there are the following lines in a D file:

#define XYZ 42

auto a = XYZ;

Then you can pass it through the preprocessor like this:

   cpp foo.d

In fact, that's one of the tricks dpp uses to make C++ headers usable in 
D code:

   https://github.com/atilaneves/dpp

As you can see above, compile-time constants are defined with 'enum' in D:

enum XYZ = 42;

auto a = XYZ;

Beware though: Do not do that with arrays though, as every usage of an 
'enum' array causes dynamic memory allocation at run time.

enum myConstants = [ 1, 2 ];

bool foo(int i) {
   import std.algorithm : canFind;
   return myConstants.canFind(i);    // <-- DON'T DO THIS
}

In addition to the enum version of an array (which you may need to use 
e.g. with 'static foreach') , also use a run-time initialized array:

// Use this e.g. for 'static foreach'
enum myConstants_enum = [ 1, 2 ];

// Use this for run-time code
immutable int[] myConstants;
shared static this() {
   // This is the initialization of the immutable array:
   myConstants = myConstants_enum;
}

bool foo(int i) {
   import std.algorithm : canFind;
   return myConstants.canFind(i);    // <-- DO THIS
}

Even though I've known about this gotcha, this wisdom comes from 
profiling my program by compiling with dmd's '-profile=gc' option. It 
was pretty obvious in the generated 'profilegc.log' file that I was 
causing such unnecessary memory allocations.

Ali
Nov 03 2019
parent Vinod K Chandran <kcvinu82 gmail.com> writes:
On Monday, 4 November 2019 at 00:20:37 UTC, Ali Çehreli wrote:

 On 11/03/2019 08:55 AM, Vinod K Chandran wrote:

 [...]


 There is nothing that stops one from using the C++ preprocessor 
 on any text file. For example, you can do the following 
 wherever GCC exists. If there are the following lines in a D 
 file:

 [...]


Sorry for the delayed reply. Thanks a lot for the hints.
Nov 09 2019