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digitalmars.D.learn - String interpolation

reply tired_eyes <pastuhov85 gmail.com> writes:
Hi,
The only example of string interpolation I've found so far is on 
Rosetta Code:

void main() {
     import std.stdio, std.string;

     "Mary had a %s lamb.".format("little").writeln;
     "Mary had a %2$s %1$s lamb.".format("little", 
"white").writeln;
}

Is this a "proper" way of string interpolation in D? This looks a 
little clumsy. Are there any better approaches? Quick skimming 
through the docs didn't give anything.
Nov 10 2015
next sibling parent wobbles <grogan.colin gmail.com> writes:
On Tuesday, 10 November 2015 at 10:21:32 UTC, tired_eyes wrote:

 Hi,
 The only example of string interpolation I've found so far is 
 on Rosetta Code:

 void main() {
     import std.stdio, std.string;

     "Mary had a %s lamb.".format("little").writeln;
     "Mary had a %2$s %1$s lamb.".format("little", 
 "white").writeln;
 }

 Is this a "proper" way of string interpolation in D? This looks 
 a little clumsy. Are there any better approaches? Quick 
 skimming through the docs didn't give anything.


Whats clumsy about it?

If it's the style (excessive use of UFCS), I'd have to agree with 
you.
Could easily have been written as:
    format("Mary had a %s lamb", "little");

which I personally think is more readable...
Nov 10 2015
prev sibling parent reply Tobias Pankrath <tobias pankrath.net> writes:
On Tuesday, 10 November 2015 at 10:21:32 UTC, tired_eyes wrote:

 Hi,
 The only example of string interpolation I've found so far is 
 on Rosetta Code:

 void main() {
     import std.stdio, std.string;

     "Mary had a %s lamb.".format("little").writeln;
     "Mary had a %2$s %1$s lamb.".format("little", 
 "white").writeln;
 }

 Is this a "proper" way of string interpolation in D? This looks 
 a little clumsy. Are there any better approaches? Quick 
 skimming through the docs didn't give anything.


std.string.format and std.format are the standard options. What 
are you missing?
Nov 10 2015
parent reply tired_eyes <pastuhov85 gmail.com> writes:
On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
wrote:

 On Tuesday, 10 November 2015 at 10:21:32 UTC, tired_eyes wrote:

 Hi,
 The only example of string interpolation I've found so far is 
 on Rosetta Code:

 void main() {
     import std.stdio, std.string;

     "Mary had a %s lamb.".format("little").writeln;
     "Mary had a %2$s %1$s lamb.".format("little", 
 "white").writeln;
 }

 Is this a "proper" way of string interpolation in D? This 
 looks a little clumsy. Are there any better approaches? Quick 
 skimming through the docs didn't give anything.


 std.string.format and std.format are the standard options. What 
 are you missing?


Ruby:
a = 1
b = 4


PHP:
$a = 1;
$b = 4;
echo "The number $a is less than $b";

D:
???
Nov 10 2015
next sibling parent reply wobbles <grogan.colin gmail.com> writes:
On Tuesday, 10 November 2015 at 10:41:52 UTC, tired_eyes wrote:

 On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
 wrote:

 On Tuesday, 10 November 2015 at 10:21:32 UTC, tired_eyes wrote:

 [...]


 std.string.format and std.format are the standard options. 
 What are you missing?


 Ruby:
 a = 1
 b = 4


 PHP:
 $a = 1;
 $b = 4;
 echo "The number $a is less than $b";

 D:
 ???


int a = 1;
int b = 4;
writefln("The number %s is less than %s", a, b);
Nov 10 2015
parent tcak <1ltkrs+3wyh1ow7kzn1k sharklasers.com> writes:
On Tuesday, 10 November 2015 at 11:22:56 UTC, wobbles wrote:

 On Tuesday, 10 November 2015 at 10:41:52 UTC, tired_eyes wrote:

 On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
 wrote:

 On Tuesday, 10 November 2015 at 10:21:32 UTC, tired_eyes 
 wrote:

 [...]


 std.string.format and std.format are the standard options. 
 What are you missing?


 Ruby:
 a = 1
 b = 4


 PHP:
 $a = 1;
 $b = 4;
 echo "The number $a is less than $b";

 D:
 ???


 int a = 1;
 int b = 4;
 writefln("The number %s is less than %s", a, b);


D:
int a = 1;
int b = 4;
writeln("The number ", a, " is less than ", b);
Nov 10 2015
prev sibling parent reply TheFlyingFiddle <kurtyan student.chalmers.se> writes:
On Tuesday, 10 November 2015 at 10:41:52 UTC, tired_eyes wrote:

 On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
 wrote:
 Ruby:
 a = 1
 b = 4


 PHP:
 $a = 1;
 $b = 4;
 echo "The number $a is less than $b";

 D:
 ???


int a = 1, b = 4;
writefln("The number %s is less than %s", a, b);

You can't do it the ruby / perl / php way in D. It could be 
possible if we had AST macros in the language but as it stands 
now it's not possible to do that.

the closest you could get is something like this:

string s = aliasFormat!("The number $a is less than $b", a, b);

or

aliasWrite!("The number $a is less than $b", a, b);

Not really recommended though as these would end up creating lots 
of template bloat.
Nov 10 2015
next sibling parent tired_eyes <pastuhov85 gmail.com> writes:
On Tuesday, 10 November 2015 at 11:29:32 UTC, TheFlyingFiddle 
wrote:

 On Tuesday, 10 November 2015 at 10:41:52 UTC, tired_eyes wrote:

 On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
 wrote:
 Ruby:
 a = 1
 b = 4


 PHP:
 $a = 1;
 $b = 4;
 echo "The number $a is less than $b";

 D:
 ???


 int a = 1, b = 4;
 writefln("The number %s is less than %s", a, b);

 You can't do it the ruby / perl / php way in D. It could be 
 possible if we had AST macros in the language but as it stands 
 now it's not possible to do that.

 the closest you could get is something like this:

 string s = aliasFormat!("The number $a is less than $b", a, b);

 or

 aliasWrite!("The number $a is less than $b", a, b);

 Not really recommended though as these would end up creating 
 lots of template bloat.


Thank everybody for the answers. I know about writefln, but I was 
hoping I just overlooked some simpler way.
Nov 10 2015
prev sibling parent reply =?UTF-8?B?TcOhcmNpbw==?= Martins <marcioapm gmail.com> writes:
On Tuesday, 10 November 2015 at 11:29:32 UTC, TheFlyingFiddle 
wrote:

 On Tuesday, 10 November 2015 at 10:41:52 UTC, tired_eyes wrote:

 On Tuesday, 10 November 2015 at 10:33:30 UTC, Tobias Pankrath 
 wrote:
 Ruby:
 a = 1
 b = 4


 PHP:
 $a = 1;
 $b = 4;
 echo "The number $a is less than $b";

 D:
 ???


 int a = 1, b = 4;
 writefln("The number %s is less than %s", a, b);

 You can't do it the ruby / perl / php way in D. It could be 
 possible if we had AST macros in the language but as it stands 
 now it's not possible to do that.

 the closest you could get is something like this:

 string s = aliasFormat!("The number $a is less than $b", a, b);

 or

 aliasWrite!("The number $a is less than $b", a, b);

 Not really recommended though as these would end up creating 
 lots of template bloat.!


You could perhaps do it with a mixin instead of AST macros:

int a = 10;
int b = 20;



One thing that would make this a lot more elegant would be the 
ability to instantiate mixins in templates. For example:

template interp(X) {
   alias interp = mixin(interpGenCode!X);
}



Quite pleasant syntax this way :)
Not sure if it's feasible to do this on the language side.
Nov 10 2015
parent reply Andrea Fontana <nospam example.com> writes:
On Tuesday, 10 November 2015 at 12:40:07 UTC, Márcio Martins 
wrote:



 Quite pleasant syntax this way :)
 Not sure if it's feasible to do this on the language side.


Yes. Here a (stupid!) proof of concept:
http://dpaste.dzfl.pl/74b1a4e3c8c6
Nov 10 2015
parent reply mw <mingwu gmail.com> writes:
On Tuesday, 10 November 2015 at 13:36:44 UTC, Andrea Fontana 
wrote:

 On Tuesday, 10 November 2015 at 12:40:07 UTC, Márcio Martins 
 wrote:



 Quite pleasant syntax this way :)
 Not sure if it's feasible to do this on the language side.


 Yes. Here a (stupid!) proof of concept:
 http://dpaste.dzfl.pl/74b1a4e3c8c6


$ cat i.d
---------------------------------------------------------------------
import std.stdio;

template interp(X) {
   alias interp = mixin(interpGenCode!X);
}

void main() {
   int a = 10;
   int b = 20;


}
---------------------------------------------------------------------
$ dmd.exe i.d





I'm wondering if this code has once worked? and seems 
dpaste.dzfl.pl no longer there.

Can we do string interpolation in D now?

Speaking of language evolution in the other thread,


https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/tokens/interpolated
string name = "Mark";
var date = DateTime.Now;
Console.WriteLine($"Hello, {name}! Today is {date.DayOfWeek}, 
it's {date:HH:mm} now.");


Python have it here:
https://www.python.org/dev/peps/pep-0498/

 import datetime
 name = 'Fred'
 age = 50
 anniversary = datetime.date(1991, 10, 12)
 f'My name is {name}, my age next year is {age+1}, my 
 anniversary is {anniversary:%A, %B %d, %Y}.'






'My name is Fred, my age next year is 51, my anniversary is 
Saturday, October 12, 1991.'

 f'He said his name is {name!r}.'






"He said his name is 'Fred'."


How can we do it in D? or when will we have it :-)?
May 20 2020
parent reply Paul Backus <snarwin gmail.com> writes:
On Wednesday, 20 May 2020 at 23:41:15 UTC, mw wrote:

 Can we do string interpolation in D now?


There's an implementation in the dub package "scriptlike":

https://code.dlang.org/packages/scriptlike#string-interpolation
May 20 2020
parent reply mw <mingwu gmail.com> writes:
On Thursday, 21 May 2020 at 01:13:27 UTC, Paul Backus wrote:

 On Wednesday, 20 May 2020 at 23:41:15 UTC, mw wrote:

 Can we do string interpolation in D now?


 There's an implementation in the dub package "scriptlike":

 https://code.dlang.org/packages/scriptlike#string-interpolation


Thank you! very nice:

// Output: The number 21 doubled is 42!
int num = 21;
writeln( mixin(interp!"The number ${num} doubled is ${num * 2}!") 
);

Is there any way to make it shorter? e.g.

writeln( s!"The number ${num} doubled is ${num * 2}!" );

i.e how to write this 's'?
May 20 2020
next sibling parent Paul Backus <snarwin gmail.com> writes:
On Thursday, 21 May 2020 at 06:57:28 UTC, mw wrote:

 On Thursday, 21 May 2020 at 01:13:27 UTC, Paul Backus wrote:

 On Wednesday, 20 May 2020 at 23:41:15 UTC, mw wrote:

 Can we do string interpolation in D now?


 There's an implementation in the dub package "scriptlike":

 https://code.dlang.org/packages/scriptlike#string-interpolation


 Thank you! very nice:

 // Output: The number 21 doubled is 42!
 int num = 21;
 writeln( mixin(interp!"The number ${num} doubled is ${num * 
 2}!") );

 Is there any way to make it shorter? e.g.

 writeln( s!"The number ${num} doubled is ${num * 2}!" );

 i.e how to write this 's'?


Unfortunately, it's not possible. Without `mixin`, there's no way 
to give the template access to local variables like `num`.
May 21 2020
prev sibling next sibling parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Thursday, 21 May 2020 at 06:57:28 UTC, mw wrote:

 i.e how to write this 's'?


gimme a like on the proposal to add to the language!

https://github.com/dlang/DIPs/pull/186

If accepted, that would let you write

i"stuff here".idup

to get an interpolated string.
May 21 2020
parent reply mw <mingwu gmail.com> writes:
On Thursday, 21 May 2020 at 12:53:50 UTC, Adam D. Ruppe wrote:

 On Thursday, 21 May 2020 at 06:57:28 UTC, mw wrote:

 i.e how to write this 's'?


 gimme a like on the proposal to add to the language!

 https://github.com/dlang/DIPs/pull/186

 If accepted, that would let you write

 i"stuff here".idup

 to get an interpolated string.


Liked.

BTW, is the .idup must be there?
May 21 2020
parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Thursday, 21 May 2020 at 17:10:31 UTC, mw wrote:

 BTW, is the .idup must be there?


It is discussed more in the github document but basically the 
proposed built-in syntax returns a generic builder thing which 
can make more than just strings. The idup specifically asks it to 
make a copy into a string as opposed to the other things it can 
provide too.
May 21 2020
parent reply ZK <z k.something> writes:
On Thursday, 21 May 2020 at 17:17:49 UTC, Adam D. Ruppe wrote:

 On Thursday, 21 May 2020 at 17:10:31 UTC, mw wrote:

 BTW, is the .idup must be there?


 It is discussed more in the github document but basically the 
 proposed built-in syntax returns a generic builder thing which 
 can make more than just strings. The idup specifically asks it 
 to make a copy into a string as opposed to the other things it 
 can provide too.


I love the extensibility of this, but perhaps there should be 
something like `ii"foo".idup` that's syntactic sugar for 
`i"foo".idup`. New users might get confused by the need for 
appending idup, and then they'll think about how other languages 
don't necessitate this perceived superfluity when using their 
interpolated string.
May 21 2020
parent ZK <z k.something> writes:
On Thursday, 21 May 2020 at 18:12:01 UTC, ZK wrote:

 I love the extensibility of this, but perhaps there should be 
 something like `ii"foo".idup` that's syntactic sugar for 
 `i"foo".idup`. New users might get confused by the need for 
 appending idup, and then they'll think about how other 
 languages don't necessitate this perceived superfluity when 
 using their interpolated string.


Whoops! I meant to say `ii"foo"`, not `ii"foo".idup`.
May 21 2020
prev sibling parent mw <mingwu gmail.com> writes:
On Thursday, 21 May 2020 at 06:57:28 UTC, mw wrote:

 On Thursday, 21 May 2020 at 01:13:27 UTC, Paul Backus wrote:

 On Wednesday, 20 May 2020 at 23:41:15 UTC, mw wrote:

 Can we do string interpolation in D now?


 There's an implementation in the dub package "scriptlike":

 https://code.dlang.org/packages/scriptlike#string-interpolation


 Thank you! very nice:

 // Output: The number 21 doubled is 42!
 int num = 21;
 writeln( mixin(interp!"The number ${num} doubled is ${num * 
 2}!") );

 Is there any way to make it shorter? e.g.

 writeln( s!"The number ${num} doubled is ${num * 2}!" );

 i.e how to write this 's'?


And for debug print, I like the output be:

The number num=21 doubled is num * 2=42!

i.e print out the string of the original expression, like the 
stringy operator in C’s macro #var
May 21 2020