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digitalmars.D.learn - a function like writeln that returns a string rather than writes to a

reply dan <dan.hitt gmail.com> writes:
I'm looking for a function something like writeln or write, but 
instead of writing to stdout, it writes to a string and returns 
the string.

So i would like something like:

import std.stdio;
import std.conv;

string write_to_string(T...)(T values ) {
   string s;
   foreach ( value; values ) s ~= to!string( value );
   return s;
}

But because this is such a standard type of thing to do, i'd like 
to use whatever the standard function is for doing it, if there 
is one.

So . . . is there one?  Like maybe some way to dress a string up 
as a file and pass it through the usual write/writeln apparatus?  
My only real requirement is that it be something really easy to 
do.

Thanks in advance for any pointers.

dan
May 01 2020
parent reply "H. S. Teoh" <hsteoh quickfur.ath.cx> writes:
On Sat, May 02, 2020 at 02:22:42AM +0000, dan via Digitalmars-d-learn wrote:

 I'm looking for a function something like writeln or write, but instead of
 writing to stdout, it writes to a string and returns the string.


[...]

	import std.format : format;
	string str = format("%s %s %s", obj1, obj2, obj3);


T

-- 
Once bitten, twice cry...
May 01 2020
parent reply dan <dan.hitt gmail.com> writes:
On Saturday, 2 May 2020 at 02:29:43 UTC, H. S. Teoh wrote:

 On Sat, May 02, 2020 at 02:22:42AM +0000, dan via 
 Digitalmars-d-learn wrote:

 I'm looking for a function something like writeln or write, 
 but instead of writing to stdout, it writes to a string and 
 returns the string.


 [...]

 	import std.format : format;
 	string str = format("%s %s %s", obj1, obj2, obj3);


 T


Thanks HS!

That looks like a good move, if format will do the string 
conversion for me.

But one thing that would be troublesome is that i would have to 
make sure to count up the %s so that they match the number of 
arguments.  I would like to do without that, just like writeln 
does.

Anyhow, though, thanks for point out format.

dan
May 01 2020
next sibling parent reply Steven Schveighoffer <schveiguy gmail.com> writes:
On 5/1/20 10:40 PM, dan wrote:

 On Saturday, 2 May 2020 at 02:29:43 UTC, H. S. Teoh wrote:

 On Sat, May 02, 2020 at 02:22:42AM +0000, dan via Digitalmars-d-learn 
 wrote:

 I'm looking for a function something like writeln or write, but 
 instead of writing to stdout, it writes to a string and returns the 
 string.


 [...]

     import std.format : format;
     string str = format("%s %s %s", obj1, obj2, obj3);


 T


 
 Thanks HS!
 
 That looks like a good move, if format will do the string conversion for 
 me.
 
 But one thing that would be troublesome is that i would have to make 
 sure to count up the %s so that they match the number of arguments.  I 
 would like to do without that, just like writeln does.


import std.conv: text;

string str = text(obj1, " ", obj2, " ", obj3);

-Steve
May 01 2020
parent dan <dan.hitt gmail.com> writes:
On Saturday, 2 May 2020 at 02:49:04 UTC, Steven Schveighoffer 
wrote:

 On 5/1/20 10:40 PM, dan wrote:

 On Saturday, 2 May 2020 at 02:29:43 UTC, H. S. Teoh wrote:

 On Sat, May 02, 2020 at 02:22:42AM +0000, dan via 
 Digitalmars-d-learn wrote:

 [...]


 [...]

     import std.format : format;
     string str = format("%s %s %s", obj1, obj2, obj3);


 T


 
 Thanks HS!
 
 That looks like a good move, if format will do the string 
 conversion for me.
 
 But one thing that would be troublesome is that i would have 
 to make sure to count up the %s so that they match the number 
 of arguments.  I would like to do without that, just like 
 writeln does.


 import std.conv: text;

 string str = text(obj1, " ", obj2, " ", obj3);

 -Steve


Awesome, thanks Steve.  That's perfect.  So the function i was 
looking for was text (or, i guess, std.conv.text).

dan
May 01 2020
prev sibling parent reply =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 5/1/20 7:40 PM, dan wrote:> On Saturday, 2 May 2020 at 02:29:43 UTC, 
H. S. Teoh wrote:

 On Sat, May 02, 2020 at 02:22:42AM +0000, dan via Digitalmars-d-learn
 wrote:

 I'm looking for a function something like writeln or write, but
 instead of writing to stdout, it writes to a string and returns the
 string.


 [...]

     import std.format : format;
     string str = format("%s %s %s", obj1, obj2, obj3);


 T


 Thanks HS!

 That looks like a good move, if format will do the string conversion for
 me.

 But one thing that would be troublesome is that i would have to make
 sure to count up the %s so that they match the number of arguments.  I
 would like to do without that, just like writeln does.


If you can live with a mildly awkward way of passing it, format() can 
take the format string at compile time as well:

   string str = format!"%s %s %s"(obj1, obj2, obj3);

You get a compilation error if format specifications don't match the 
arguments. (There are bug reports about that check but it mostly works 
great.)

Ali
May 02 2020
parent dan <dan.hitt gmail.com> writes:
On Saturday, 2 May 2020 at 10:36:47 UTC, Ali Çehreli wrote:

 On 5/1/20 7:40 PM, dan wrote:> On Saturday, 2 May 2020 at 
 02:29:43 UTC, H. S. Teoh wrote:

 On Sat, May 02, 2020 at 02:22:42AM +0000, dan via




 Digitalmars-d-learn

 wrote:

 I'm looking for a function something like writeln or write,






 but

 instead of writing to stdout, it writes to a string and






 returns the

 string.


 [...]

     import std.format : format;
     string str = format("%s %s %s", obj1, obj2, obj3);


 T


 Thanks HS!

 That looks like a good move, if format will do the string


 conversion for

 me.

 But one thing that would be troublesome is that i would have


 to make

 sure to count up the %s so that they match the number of


 arguments.  I

 would like to do without that, just like writeln does.


 If you can live with a mildly awkward way of passing it, 
 format() can take the format string at compile time as well:

   string str = format!"%s %s %s"(obj1, obj2, obj3);

 You get a compilation error if format specifications don't 
 match the arguments. (There are bug reports about that check 
 but it mostly works great.)

 Ali


Thanks Ali.

That's also a good point, and would remove one of my qualms about 
all of the %s reps.

So if for any reason i cannot use the text function (or if i want 
to double check on the types of the objects) this would be a good 
thing to use.

dan
May 02 2020