www.digitalmars.com         C & C++   DMDScript  

digitalmars.D - Bragging about Unix and D

reply Georg Wrede <georg nospam.org> writes:
I just came to town. I had an interesting debate with somebody who 
didn't appreciate Unix (or Linux) or D enough. So I showed to him that 
interacting with a Unix machine is discussing, and that when you're good 
at it, you talk with sentences, not single commands (as in DOS). He 
demanded examples, and one I gave him was to ask the machine for a 
multiplication table. I conjured up the following sentence:

$ for a in {0..9};do for b in {0..9};do echo -ne `dc -e"$a $b 
*pq"`"\011";done;echo;done

which gave a nice table:

0     0     0     0     0     0     0     0     0     0
0     1     2     3     4     5     6     7     8     9
0     2     4     6     8     10    12    14    16    18
0     3     6     9     12    15    18    21    24    27
0     4     8     12    16    20    24    28    32    36
0     5     10    15    20    25    30    35    40    45
0     6     12    18    24    30    36    42    48    54
0     7     14    21    28    35    42    49    56    63
0     8     16    24    32    40    48    56    64    72
0     9     18    27    36    45    54    63    72    81

Now, I wanted to do the same thing with DMD, but I failed miserably.

What I tried to do was some kind of template magic (a la Don) that 
prints something like this at compile time, without even creating an 
executable.

-- Sigh, can't win 'em all.
Aug 23 2006
next sibling parent BCS <BCS pathlink.com> writes:
Georg Wrede wrote:
 I just came to town. I had an interesting debate with somebody who 
 didn't appreciate Unix (or Linux) or D enough. So I showed to him that 
 interacting with a Unix machine is discussing, and that when you're good 
 at it, you talk with sentences, not single commands (as in DOS). He 
 demanded examples, and one I gave him was to ask the machine for a 
 multiplication table. I conjured up the following sentence:
 
 $ for a in {0..9};do for b in {0..9};do echo -ne `dc -e"$a $b 
 *pq"`"\011";done;echo;done
 
 which gave a nice table:
 
 0     0     0     0     0     0     0     0     0     0
 0     1     2     3     4     5     6     7     8     9
 0     2     4     6     8     10    12    14    16    18
 0     3     6     9     12    15    18    21    24    27
 0     4     8     12    16    20    24    28    32    36
 0     5     10    15    20    25    30    35    40    45
 0     6     12    18    24    30    36    42    48    54
 0     7     14    21    28    35    42    49    56    63
 0     8     16    24    32    40    48    56    64    72
 0     9     18    27    36    45    54    63    72    81
 
 Now, I wanted to do the same thing with DMD, but I failed miserably.
 
 What I tried to do was some kind of template magic (a la Don) that 
 prints something like this at compile time, without even creating an 
 executable.
 
 -- Sigh, can't win 'em all.

Crud, now I'm going to have to try that!
Aug 23 2006
prev sibling parent reply Tom S <h3r3tic remove.mat.uni.torun.pl> writes:
Georg Wrede wrote:
 What I tried to do was some kind of template magic (a la Don) that 
 prints something like this at compile time, without even creating an 
 executable.
 
 -- Sigh, can't win 'em all.

Not hard at all... const int numWidth = 6; const int width = 10; const int height = 10; template itoa(int i) { static if (i < 10) { const char[] itoa = "" ~ "0123456789"[i]; } else { const char[] itoa = itoa!(i/10) ~ "0123456789"[i%10]; } } template nspaces(int n) { static if (n > 0) { const char[] nspaces = " " ~ nspaces!(n - 1); } else { const char[] nspaces = ""; } } template itoa_pad(int i) { const char[] itoa_pad = itoa!(i) ~ nspaces!(numWidth - itoa!(i).length); } template row(int hpos, int i = 0) { static if (i+1 < width) { const char[] row = itoa_pad!(i*hpos) ~ row!(hpos, i+1); } else { const char[] row = itoa_pad!(i*hpos); } } template table(int i = 0) { pragma (msg, row!(i)); static if (i+1 < height) { mixin .table!(i+1) table; } else { alias void table; } } alias table!() draw; -- Tomasz Stachowiak
Aug 23 2006
parent reply Sean Kelly <sean f4.ca> writes:
Tom S wrote:
 
 template table(int i = 0) {
     pragma (msg, row!(i));
 
     static if (i+1 < height) {
         mixin .table!(i+1) table;
     } else {
         alias void table;
     }
 }

Huh, now there's a use for mixin I can appreciate. Nice work. Sean
Aug 24 2006
parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Sean Kelly wrote:
 Tom S wrote:
 template table(int i = 0) {
     pragma (msg, row!(i));

     static if (i+1 < height) {
         mixin .table!(i+1) table;
     } else {
         alias void table;
     }
 }

Huh, now there's a use for mixin I can appreciate. Nice work.

but s/mixin/alias/ will work just as well. :)
Aug 24 2006
next sibling parent Sean Kelly <sean f4.ca> writes:
Oskar Linde wrote:
 Sean Kelly wrote:
 Tom S wrote:
 template table(int i = 0) {
     pragma (msg, row!(i));

     static if (i+1 < height) {
         mixin .table!(i+1) table;
     } else {
         alias void table;
     }
 }

Huh, now there's a use for mixin I can appreciate. Nice work.

but s/mixin/alias/ will work just as well. :)

True :-) Though this got me thinking again about iterative code generation in D--I've been too occupied with other things to get fancy with template programming recently. Working arount ITI limitations is about the extent of it. Sean
Aug 24 2006
prev sibling next sibling parent Tom S <h3r3tic remove.mat.uni.torun.pl> writes:
Oskar Linde wrote:
 Sean Kelly wrote:
 Tom S wrote:
 template table(int i = 0) {
     pragma (msg, row!(i));

     static if (i+1 < height) {
         mixin .table!(i+1) table;
     } else {
         alias void table;
     }
 }

Huh, now there's a use for mixin I can appreciate. Nice work.

but s/mixin/alias/ will work just as well. :)

Well, it's a typo, it was supposed to be an alias :D
Aug 24 2006
prev sibling parent Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:
Oskar Linde wrote:
 Sean Kelly wrote:
 Tom S wrote:
 template table(int i = 0) {
     pragma (msg, row!(i));

     static if (i+1 < height) {
         mixin .table!(i+1) table;
     } else {
         alias void table;
     }
 }

Huh, now there's a use for mixin I can appreciate. Nice work.

but s/mixin/alias/ will work just as well. :)

Here it does, but in the general case it doesn't work as well. First since the mixin creates a (unique) new template instance, that might differ significantly if such template has run-time members. Second, you can't use a mixin in an instruction block, and an alias can (and I've used that). So that's not a good use for mixin, use alias for instantiating dummy template instances. :) Also the ... else { alias void table; } is not necessary. ;)
Aug 24 2006