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digitalmars.D.learn - Compare types with `static if` in template function.

reply "vladde" <v vladde.net> writes:
I want to have a template function where I can throw in some 
stuff in the parameters, then run foreach+static ifs and check 
what type the current is. From my project clayers[1], I've taken 
out some parts. (Note the current code does not compile.)
This is what I have so far:


struct XY {size_t x, y;}
alias fg = colorize.fg; //[2]
[...]
void changeSlot(C...)(XY xy, C changes){
     foreach(c; changes){
         static if(is(typeof(c) == dchar) || is(typeof(c) == char))
         {
             slots[xy.y][xy.x].character = c;
         }
         else if(is(typeof(c) == fg))
         {
             slots[xy.y][xy.x].fg = C;
         }
     }
}
[...]
changeSlot(XY(10, 15), fg.red);


For this demonstation I've chosen to only check for `char` and 
`fg`, but it's intended to check for multiple different types. 
(See [1])

Now when I try to compile, I get "Error: more than one argument 
for construction of int" for checking against fg. HOWEVER, the 
code functions properly when checking the type for characters. 
 From what I understand, my thinking works, but checking with `fg` 
is causing some crux-flux. `fg` is created from a template, 
please take a look at [2].

What am I doing wrong when I check for the type of `fg`?

TL;DR: Is there a way to check the type of `fg` with an static if?

[1] = 
https://github.com/vladdeSV/clayers/blob/change-slot/source/clayers.d#L323
[2] = 
https://github.com/yamadapc/d-colorize/blob/master/source/colorize/colors.d#L37
Jul 29 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 07/29/2015 10:48 AM, vladde wrote:


          static if(is(typeof(c) == dchar) || is(typeof(c) == char))
          {
              slots[xy.y][xy.x].character = c;
          }
          else if(is(typeof(c) == fg))


I don't know whether it is the reason here but you fell for one of the D 
traps. :( Most definitely, you want an 'else static if' there.

Otherwise, for the fg case, what ends up in your code to be compiled is 
this:

   if(is(typeof(c) == fg))

Ali
Jul 29 2015
parent reply "vladde" <v vladde.net> writes:
On Wednesday, 29 July 2015 at 17:52:45 UTC, Ali Çehreli wrote:

 On 07/29/2015 10:48 AM, vladde wrote:


          static if(is(typeof(c) == dchar) || is(typeof(c) ==


 char))

          {
              slots[xy.y][xy.x].character = c;
          }
          else if(is(typeof(c) == fg))


 I don't know whether it is the reason here but you fell for one 
 of the D traps. :( Most definitely, you want an 'else static 
 if' there.

 Otherwise, for the fg case, what ends up in your code to be 
 compiled is this:

   if(is(typeof(c) == fg))

 Ali


Apparently, if I only check for a character the code compiles 
without the need of static if.

if(is(typeof(c) == dchar) || is(typeof(c) == char)){ 
slots[xy.y][xy.x].character = c; } //Compiles and works as 
expected
Jul 29 2015
parent reply "vladde" <v vladde.net> writes:
On Wednesday, 29 July 2015 at 18:04:48 UTC, vladde wrote:

 Apparently, if I only check for a character the code compiles 
 without the need of static if.

 if(is(typeof(c) == dchar) || is(typeof(c) == char)){ 
 slots[xy.y][xy.x].character = c; } //Compiles and works as 
 expected


And changing all if statements to static if still does not 
compile.
Jul 29 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 07/29/2015 11:08 AM, vladde wrote:

 On Wednesday, 29 July 2015 at 18:04:48 UTC, vladde wrote:

 Apparently, if I only check for a character the code compiles without
 the need of static if.

 if(is(typeof(c) == dchar) || is(typeof(c) == char)){
 slots[xy.y][xy.x].character = c; } //Compiles and works as expected


 And changing all if statements to static if still does not compile.


The error may be the capital C in the else branch. (?)

Can you provide complete code please? The following compiles with dmd 2.067:

struct XY {size_t x, y;}

private template color_type(int offset)
{
   static enum type : int
   {
     init = 39 + offset,

     black   = 30 + offset,
     red     = 31 + offset,
     green   = 32 + offset,
     yellow  = 33 + offset,
     blue    = 34 + offset,
     magenta = 35 + offset,
     cyan    = 36 + offset,
     white   = 37 + offset,

     light_black   = 90 + offset,
     light_red     = 91 + offset,
     light_green   = 92 + offset,
     light_yellow  = 93 + offset,
     light_blue    = 94 + offset,
     light_magenta = 95 + offset,
     light_cyan    = 96 + offset,
     light_white   = 97 + offset
   }
}

alias color_type!0 .type fg;

// alias fg = colorize.fg; //[2]

void changeSlot(C...)(XY xy, C changes){
     foreach(c; changes){
         static if(is(typeof(c) == dchar) || is(typeof(c) == char))
         {
             // slots[xy.y][xy.x].character = c;
         }
         else if(is(typeof(c) == fg))
         {
             // slots[xy.y][xy.x].fg = C;
         }
     }
}

void main()
{
     changeSlot(XY(10, 15), fg.red);
}

Ali
Jul 29 2015
parent reply "vladde" <v vladde.net> writes:
On Wednesday, 29 July 2015 at 18:14:11 UTC, Ali Çehreli wrote:

         else if(is(typeof(c) == fg))
         {
             // slots[xy.y][xy.x].fg = C;
         }


The error occurs when the commented line is run. The full code 
can be viewed at 
https://github.com/vladdeSV/clayers/blob/change-slot/source/clayers.d
Jul 29 2015
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 07/29/2015 11:54 AM, vladde wrote:

 On Wednesday, 29 July 2015 at 18:14:11 UTC, Ali Çehreli wrote:

         else if(is(typeof(c) == fg))
         {
             // slots[xy.y][xy.x].fg = C;
         }


 The error occurs when the commented line is run. The full code can be
 viewed at
 https://github.com/vladdeSV/clayers/blob/change-slot/source/clayers.d


You seem to be using type names instead of member names:

             static if(is(typeof(c) == dchar) || is(typeof(c) == char))
             {
                 slots[xy.y][xy.x].character = c;
             }
             else if(is(typeof(c) == fg))
             {
                 slots[xy.y][xy.x].fg = c;

Should be

... color = c;

             }
             else if(is(typeof(c) == bg))
             {
                 slots[xy.y][xy.x].bg = c;

... background = c;

             }
             else if(is(typeof(c) == md))
             {
                 slots[xy.y][xy.x].md = c;

... mode = c;

             }

Ali
Jul 29 2015
parent "Vladde Nordholm" <v vladde.net> writes:
On Wednesday, 29 July 2015 at 22:40:08 UTC, Ali Çehreli wrote:

 You seem to be using type names instead of member names:

             static if(is(typeof(c) == dchar) || is(typeof(c) == 
 char))
             {
                 slots[xy.y][xy.x].character = c;
             }
             else if(is(typeof(c) == fg))
             {
                 slots[xy.y][xy.x].fg = c;

 Should be

 ... color = c;

             }
             else if(is(typeof(c) == bg))
             {
                 slots[xy.y][xy.x].bg = c;

 ... background = c;

             }
             else if(is(typeof(c) == md))
             {
                 slots[xy.y][xy.x].md = c;

 ... mode = c;

             }

 Ali


Thank you! This was a mistake on my end. Really glad you spotted 
it, saved me quite some headaches!
Jul 30 2015