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digitalmars.D.learn - 'pp' for D?

reply "linkrope" <linkrope github.com> writes:
I want to pretty-print the representation of a value of a generic 
type T.
In Ruby, I would use 'pp':

     value = 'hello'

     value = 42


Now, value.to!string eliminates the quotes, should value be of 
type string.
As a workaround, I put the value into an array to make use of the 
"undocumented" function formatElement:

     "%(%s%)".format([value])

Ugly! Where does Phobos hide the function I'm looking for?
Sep 29 2013
next sibling parent reply "monarch_dodra" <monarchdodra gmail.com> writes:
On Sunday, 29 September 2013 at 14:31:15 UTC, linkrope wrote:

 As a workaround, I put the value into an array to make use of 
 the "undocumented" function formatElement:

     "%(%s%)".format([value])


That seems excessive. What happened to format(`"%s"`, s) or 
format("\"%s\"", s) or text('"', s, '"')?


 Where does Phobos hide the function I'm looking for?


I don't have a solution that's "convenient" enough to satisfy you.
Sep 29 2013
parent reply "linkrope" <linkrope github.com> writes:
On Sunday, 29 September 2013 at 18:14:03 UTC, monarch_dodra wrote:

 On Sunday, 29 September 2013 at 14:31:15 UTC, linkrope wrote:

 As a workaround, I put the value into an array to make use of 
 the "undocumented" function formatElement:

    "%(%s%)".format([value])


 That seems excessive. What happened to format(`"%s"`, s) or 
 format("\"%s\"", s) or text('"', s, '"')?


Of course, this works well when I know that the value is of type 
string.

But I have a template and I want to print the representation of 
(T value):
"hello" (with quotes) or just 42 (without)

Phobos does this for array elements, but it seems that there's 
nothing like 'repr'?
Sep 29 2013
parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 09/29/2013 03:38 PM, linkrope wrote:

 On Sunday, 29 September 2013 at 18:14:03 UTC, monarch_dodra wrote:

 On Sunday, 29 September 2013 at 14:31:15 UTC, linkrope wrote:

 As a workaround, I put the value into an array to make use of the
 "undocumented" function formatElement:

    "%(%s%)".format([value])


 That seems excessive. What happened to format(`"%s"`, s) or
 format("\"%s\"", s) or text('"', s, '"')?


 Of course, this works well when I know that the value is of type string.

 But I have a template and I want to print the representation of (T value):
 "hello" (with quotes) or just 42 (without)

 Phobos does this for array elements, but it seems that there's nothing
 like 'repr'?


I don't know a Phobos function either but the following should work:

import std.stdio;
import std.traits;

void pp(T)(File output, T value)
{
     static if (isSomeString!T) {
         output.writef(`"%s"`, value);

     } else {
         output.write(value);
     }
}

void pp(T)(T value)
{
     pp(stdout, value);
}

void main()
{
     pp("hello");
     pp(42);
}

Ali
Sep 29 2013
next sibling parent "monarch_dodra" <monarchdodra gmail.com> writes:
On Monday, 30 September 2013 at 04:20:32 UTC, Ali Çehreli wrote:

 On 09/29/2013 03:38 PM, linkrope wrote:

 On Sunday, 29 September 2013 at 18:14:03 UTC, monarch_dodra 
 wrote:

 On Sunday, 29 September 2013 at 14:31:15 UTC, linkrope wrote:

 As a workaround, I put the value into an array to make use 
 of the
 "undocumented" function formatElement:

   "%(%s%)".format([value])


 That seems excessive. What happened to format(`"%s"`, s) or
 format("\"%s\"", s) or text('"', s, '"')?


 Of course, this works well when I know that the value is of 
 type string.

 But I have a template and I want to print the representation 
 of (T value):
 "hello" (with quotes) or just 42 (without)

 Phobos does this for array elements, but it seems that there's 
 nothing
 like 'repr'?


 I don't know a Phobos function either but the following should 
 work:

 [SNIP]
     static if (isSomeString!T) {


This should also take into acount enums, as they get their own 
printing.

It should either use std.conv's private "isExactSomeString", or 
use:
static if (isSomeString!T && !is(T == enum)
Sep 29 2013
prev sibling parent reply "linkrope" <linkrope github.com> writes:
On Monday, 30 September 2013 at 04:20:32 UTC, Ali Çehreli wrote:

 I don't know a Phobos function either but the following should 
 work:

 import std.stdio;
 import std.traits;

 void pp(T)(File output, T value)
 {
     static if (isSomeString!T) {
         output.writef(`"%s"`, value);

     } else {
         output.write(value);
     }
 }

 void pp(T)(T value)
 {
     pp(stdout, value);
 }

 void main()
 {
     pp("hello");
     pp(42);
 }

 Ali


OK.

But putting quotes around a string value is obviously not enough.
What if the string contains a quote? "hell\"o" would become 
`"hell"o"`!

Seems, I have the choice between:

string repr(T)(T value)
{
     auto writer = appender!string();
     auto fmt = FormatSpec!char("%s");

     formatElement(writer, value, fmt);
     return writer.data;
}

(relying on the "undocumented" formatElement),
or the aforementioned array detour:

string repr(T)(T value)
{
     return "%(%s%)".format([value]);
}
Sep 30 2013
parent reply "John Colvin" <john.loughran.colvin gmail.com> writes:
On Monday, 30 September 2013 at 21:24:28 UTC, linkrope wrote:

 But putting quotes around a string value is obviously not 
 enough.
 What if the string contains a quote? "hell\"o" would become 
 `"hell"o"`!


Would would you want it be become?
Oct 01 2013
next sibling parent "monarch_dodra" <monarchdodra gmail.com> writes:
On Tuesday, 1 October 2013 at 09:21:44 UTC, John Colvin wrote:

 On Monday, 30 September 2013 at 21:24:28 UTC, linkrope wrote:

 But putting quotes around a string value is obviously not 
 enough.
 What if the string contains a quote? "hell\"o" would become 
 `"hell"o"`!


 Would would you want it be become?


Don't understand. Did you mean "Would would you want it be 
become"?

I think he meant that he *wanted* it to become "hell\"o". I said: 
"why don't you just print `"%s"`, to which he retorted by saying 
it would choke on his input of `hell"o`, which would print:
"hell"o"
Which would be wrong.
Oct 01 2013
prev sibling parent "qznc" <qznc web.de> writes:
On Tuesday, 1 October 2013 at 09:21:44 UTC, John Colvin wrote:

 On Monday, 30 September 2013 at 21:24:28 UTC, linkrope wrote:

 But putting quotes around a string value is obviously not 
 enough.
 What if the string contains a quote? "hell\"o" would become 
 `"hell"o"`!


 Would would you want it be become?


I believe the basic idea of repr and friends is to output 
language literals. You could copy&paste the output back into a 
source file and use it.
Oct 01 2013
prev sibling next sibling parent reply "bearophile" <bearophileHUGS lycos.com> writes:
linkrope:


 Where does Phobos hide the function I'm looking for?


Surely Phobos should add a prettyPrinting() function, like the 
function of Python standard library.

Bye,
bearophile
Sep 30 2013
parent reply Jacob Carlborg <doob me.com> writes:
On 2013-09-30 23:56, bearophile wrote:


 Surely Phobos should add a prettyPrinting() function, like the function
 of Python standard library.


I would rather have function that generates a pretty representation of a 
given value. Then it either can be used to print the representation or 
something else.

-- 
/Jacob Carlborg
Oct 01 2013
next sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Jacob Carlborg:


 I would rather have function that generates a pretty 
 representation of a given value. Then it either can be used to 
 print the representation or something else.


That's the point of the Python pprint() (pretty print) function 
:-)

Bye,
bearophile
Oct 01 2013
prev sibling parent reply "linkrope" <linkrope github.com> writes:
On Tuesday, 1 October 2013 at 07:30:06 UTC, Jacob Carlborg wrote:

 On 2013-09-30 23:56, bearophile wrote:


 Surely Phobos should add a prettyPrinting() function, like the 
 function
 of Python standard library.


 I would rather have function that generates a pretty 
 representation of a given value. Then it either can be used to 
 print the representation or something else.


How about "%r" in 'format'?

Then for arrays, "%(%s, %)" would in fact be "%(%r, %)" while 
"%-(%s, %)" would in fact be "%(%s, %)" - breaking existing code; 
punishable by 'xxformat' for at least one year :-)
Oct 01 2013
parent reply "monarch_dodra" <monarchdodra gmail.com> writes:
On Tuesday, 1 October 2013 at 19:47:16 UTC, linkrope wrote:

 On Tuesday, 1 October 2013 at 07:30:06 UTC, Jacob Carlborg 
 wrote:

 On 2013-09-30 23:56, bearophile wrote:


 Surely Phobos should add a prettyPrinting() function, like 
 the function
 of Python standard library.


 I would rather have function that generates a pretty 
 representation of a given value. Then it either can be used to 
 print the representation or something else.


 How about "%r" in 'format'?

 Then for arrays, "%(%s, %)" would in fact be "%(%r, %)" while 
 "%-(%s, %)" would in fact be "%(%s, %)" - breaking existing 
 code; punishable by 'xxformat' for at least one year :-)


%r is already taken: It means "raw". It's used as a way to use 
formatting, even when writing in a binary file. You can even use 
"%+r" and "%-r" to specify the endian-ness you want to write in. 
It's fun. Makes writing file headers *real* easy.
Oct 01 2013
parent "bearophile" <bearophileHUGS lycos.com> writes:
monarch_dodra:


 %r is already taken: It means "raw". It's used as a way to use 
 formatting, even when writing in a binary file. You can even 
 use "%+r" and "%-r" to specify the endian-ness you want to 
 write in. It's fun. Makes writing file headers *real* easy.


I didn't know that -.-

Bye,
bearophile
Oct 01 2013
prev sibling next sibling parent "Daniel Davidson" <nospam spam.com> writes:
On Sunday, 29 September 2013 at 14:31:15 UTC, linkrope wrote:

 I want to pretty-print the representation of a value of a 
 generic type T.
 In Ruby, I would use 'pp':

     value = 'hello'

     value = 42


 Now, value.to!string eliminates the quotes, should value be of 
 type string.
 As a workaround, I put the value into an array to make use of 
 the "undocumented" function formatElement:

     "%(%s%)".format([value])

 Ugly! Where does Phobos hide the function I'm looking for?


I have one at: 
https://github.com/patefacio/d-help/blob/master/d-help/pprint/pp.d

The following code outputs the text below:

     import std.stdio;
     import pprint.pp;

     enum Color {
       Red,
       White,
       Blue
     }

     struct R {
       int x = 22;
       string s = "foobar";
     }

     struct S {
       int i;
       R r;
     }

     struct T {
       int []i;
       string []j;
     }


     void main() {
       auto s = S(3);
       auto t = T([1,2,3], ["a", "b", "c"]);

       writeln(pp(Color.Red));
       writeln(pp(42));
       writeln(pp("hello"));
       writeln(pp(s));
       writeln(pp(t));
     }


Outputs

     Red
     42
     "hello"
     {
      (S).i = 3
      (S).r = {
       (R).x = 22
       (R).s = "foobar"
      }
     }
     {
      (T).i = [
       [0]->1
       [1]->2
       [2]->3
      ]
      (T).j = [
       [0]->"a"
       [1]->"b"
       [2]->"c"
      ]
     }
Sep 30 2013
prev sibling parent Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> writes:
On Sun, 29 Sep 2013 16:31:14 +0200
"linkrope" <linkrope github.com> wrote:


 I want to pretty-print the representation of a value of a generic 
 type T.
 In Ruby, I would use 'pp':
 
      value = 'hello'

      value = 42

 
 Now, value.to!string eliminates the quotes, should value be of 
 type string.
 As a workaround, I put the value into an array to make use of the 
 "undocumented" function formatElement:
 
      "%(%s%)".format([value])
 
 Ugly! Where does Phobos hide the function I'm looking for?


How 'bout either of these?:

void pp(T)(T value) {
	writefln("%(%s%)", [value]);
}

string prettyVal(T)(T value) {
	return "%(%s%)".format([value]);
}

pp(...whatever...);
string s = prettyVal(...whatever...);
Oct 01 2013