• "bearophile" <bearophileHUGS lycos.com> Mar 20 2012
• "bearophile" <bearophileHUGS lycos.com> Mar 20 2012
• Andrej Mitrovic <andrej.mitrovich gmail.com> Mar 20 2012
• "bearophile" <bearophileHUGS lycos.com> Mar 20 2012
• "Kenji Hara" <k.hara.pg gmail.com> Mar 22 2012

"bearophile" <bearophileHUGS lycos.com> writes:

This code:


import std.stdio;
void main() {
      auto mat = [[1, 2, 3],
                  [4, 5, 6],
                  [7, 8, 9]];

      writefln("%(%(%d %)\n%)", mat);
      writeln();

      writefln("[%(%(%d %)\n%)]", mat);
      writeln();

      writefln("[%([%(%d %)]\n%)]", mat);
      writeln();
}


Prints:

1 2 3
4 5 6
7 8 9

[1 2 3
4 5 6
7 8 9]

[[1 2 3]
[4 5 6]
[7 8 9]


Do you know why the last closed square bracket is missing?

----------------------

The following is just a note. The formatting syntax for arrays is
rather powerful, it allows you to pretty print a matrix:

import std.stdio;
void main() {
      auto mat = [[1, 2, 3],
                  [4, 15, 6],
                  [7, 8, 9]];
      writefln("[%([%(%2d, %)],\n %)]]", mat);
}


That outputs:

[[ 1,  2,  3],
   [ 4, 15,  6],
   [ 7,  8,  9]]

But all the columns must have the same width, so the first and
third column waste space. So you can't write:

[[1,  2, 3],
   [4, 15, 6],
   [7,  8, 9]]

To do it you have to pre-process the matrix, and create a matrix
of already smartly formatted strings, or better write a pretty
printing function (that belongs in Phobos. Python has it in its
'pprint' standard library module).

Bye,
bearophile

"bearophile" <bearophileHUGS lycos.com> writes:

 import std.stdio;
 void main() {
      auto mat = [[1, 2, 3],
                  [4, 15, 6],
                  [7, 8, 9]];
      writefln("[%([%(%2d, %)],\n %)]]", mat);
 }


 That outputs:

 [[ 1,  2,  3],
   [ 4, 15,  6],
   [ 7,  8,  9]]


Sorry, the dlang forum online interface has added an extra 
leading space on only certain lines.

I use 4 spaces indents in such code.

Bye,
bearophile

Andrej Mitrovic <andrej.mitrovich gmail.com> writes:

On 3/21/12, bearophile <bearophileHUGS lycos.com> wrote:
 The following is just a note. The formatting syntax for arrays is
 rather powerful, it allows you to pretty print a matrix.


I didn't know that! Is this documented anywhere?

"bearophile" <bearophileHUGS lycos.com> writes:

Andrej Mitrovic:

 I didn't know that! Is this documented anywhere?


It's documented formally, but I see no usage examples of the 
nested formatting syntax:
http://dlang.org/phobos/std_format.html

Bye,
bearophile

"Kenji Hara" <k.hara.pg gmail.com> writes:

On Wednesday, 21 March 2012 at 01:26:23 UTC, bearophile wrote:
 import std.stdio;
 void main() {
      auto mat = [[1, 2, 3],
                  [4, 5, 6],
                  [7, 8, 9]];

      writefln("%(%(%d %)\n%)", mat);
      writeln();

      writefln("[%(%(%d %)\n%)]", mat);
      writeln();

      writefln("[%([%(%d %)]\n%)]", mat);
      writeln();
 }

 Prints:

 1 2 3
 4 5 6
 7 8 9

 [1 2 3
 4 5 6
 7 8 9]

 [[1 2 3]
 [4 5 6]
 [7 8 9]


 Do you know why the last closed square bracket is missing?


You can use %| format specifier to specify element separator.

(It was proposed in 
https://github.com/D-Programming-Language/phobos/pull/298 .
It is not yet documented, but already merged in Phobos.)

import std.stdio;
void main() {
      auto mat = [[1, 2, 3],
                  [4, 5, 6],
                  [7, 8, 9]];

      writefln("[%([%(%d %)]%|\n%)]", mat);
      // specify "\n" as a separator
}

Prints:

[[1 2 3]
[4 5 6]
[7 8 9]]