Is there a Delphi equivalent of WriteStr ?

[Martin Liddle 1]

I am porting some code from the Gnu Pascal compiler that makes extensive use of WriteStr which is an ISO 10206 Extended Pascal extension; is there a Delphi equivalent?   For those not familiar with WriteStr, WriteStr(S,Args) behaves like Write, except that it stores its output in the string variable S instead of a file. 

Edited February 7, 2023 by Martin Liddle

[uligerhardt 18]

That should be just Str.

[David Schwartz 426]

I use Format for that.

[Virgo 18]

9 hours ago, uligerhardt said:

That should be just Str.

Str just converts number to string.... As David Schwartz writes, format is functionally similar, but it has different syntax (format is more like C printf than Pascal Write).  But unlike fpc Delphi does not seem to have WriteStr.

[uligerhardt 18]

Maybe something like this: Delphi-PRAXiS - Einzelnen Beitrag anzeigen - TextFile Writeln für Klasse verfügbar machen. (delphipraxis.net)

[Sherlock 663]

Hmm almost sounds like a job for TWriter.WriteString which writes to a TStream. If you don't want it to be a file, it could be a TStringStream.

[Virgo 18]

33 minutes ago, Sherlock said:

Hmm almost sounds like a job for TWriter.WriteString which writes to a TStream. If you don't want it to be a file, it could be a TStringStream.

No it is not. TWriter.WriteString writes strings.

example:
 

program writeStrTest;
{$mode objfpc}
{$H+}
var
  x: extended;
  y: Int64;
  s, s2: string;
begin
  x := 193.17;
  y := 123746214;
  s := 'Some tekst';
  WriteStr(s2, 'x = ', x:10:4, ', y = ', y:10, ', s = ', s:20);
  WriteLn(s2);
end.

will output

x =   193.1700, y =  123746214, s =           Some tekst

 

format is closest thing in Delphi, but format does not have ability to pad values with spaces (if user requires it).

 

 

[Lars Fosdal 1792]

UliGerhardt's solution could be wrapped - but it would be challenging to make threadsafe.

 

It would treat s2 like a file, and write to the file.

With a helper class, it would be possible to read the last written content out from s2 as a String again.

 

Is it unthinkable to simply replace

WriteStr(s2,
with

Writeln(

?

[Fr0sT.Brutal 900]

36 minutes ago, Virgo said:

but format does not have ability to pad values with spaces

it has: `%10d`

 

You can borrow the code from GNU Pascal but you'll have to wrap arguments into array. Delphi doesn't support user functions with undefined number of arguments

Edited February 8, 2023 by Fr0sT.Brutal

[Virgo 18]

7 minutes ago, Lars Fosdal said:

Is it unthinkable to simply replace

WriteStr(s2,
with

Writeln(

?

That only applies, if goal is to write to file or stdout. My example code did writeln to result string just to get, what the value was. Real use can be different. But depending, what WriteStr features were used it should be possible to rewrite it in Delphi.

[Lars Fosdal 1792]

I see. How many of these do you need to replace?

If it is not a massive number, I would go for Format. 

It can both left and right pad with spaces if so is required, but converting the WriteStr formats will be a chore.

 

WriteStr(s2, 'x = ', x:10:4, ', y = ', y:10, ', s = ', s:20);
s2 := Format('x = %10.4f, y = %10d, s = %-20s, [x, y, s]);

The usual f'up here is to either missalign the format string and the number of params, or have the wrong type variable in relation to the format specifier.

[Virgo 18]

11 minutes ago, Fr0sT.Brutal said:

it has: `%10d`

 

I somehow managed to miss width parameter. With it it is really possible to rewrite WriteStr as format and since Delphi does not have WriteStr, it is best solution. Better than trying to hack around with file.

So:

s2 := format('x = %10.4f, y = %10d, s = %20s', [x, y, s]);

would be same as

WriteStr(s2, 'x = ', x:10:4, ', y = ', y:10, ', s = ', s:20);

 

Edited February 8, 2023 by Virgo

[Lars Fosdal 1792]

Added example: caveat - specifiers from the top of my head 😛

[PeterBelow 238]

20 hours ago, Martin Liddle said:

I am porting some code from the Gnu Pascal compiler that makes extensive use of WriteStr which is an ISO 10206 Extended Pascal extension; is there a Delphi equivalent?   For those not familiar with WriteStr, WriteStr(S,Args) behaves like Write, except that it stores its output in the string variable S instead of a file. 

It used to be possible to kind of redirect the output of Write/WriteLn using something called a "text-file device driver". I found some ancient unit of mine in the newsgroup archives, see https://codenewsfast.com/cnf/article/0/permalink.art-ng1618q5913 . If the link does not work search for "Unit StreamIO". It contains a AssignStream procedure you can use to attach a stream (in this case a TStringstream would be appropriate) to a Textfile variable. Output to this variable would then end up in the stream, from which you can get the content as a string.

 

As I said this is old code, I have no idea how it behaves under Unicode-enabled versions of Delphi.

[uligerhardt 18]

36 minutes ago, PeterBelow said:

It used to be possible to kind of redirect the output of Write/WriteLn using something called a "text-file device driver".

That's the core of Uwe's code I linked to.

[Marco V 3]

Peter: that generally still works as of Delphi Seattle, I use it regularly. But it might have unicode issues due to working over a pansichar buffer, which would cause corruption when unicodestring is converted to array of ansichar. There is some MBCS support in textrec too but I have no experience with it, and probably would require updating devin/out.

 

As so often, a workaround for that could be  setting the ansi codepage to UTF-8 per Windows 10-1805+ manifest, but that of course has very wide consequences. I don't have much experience with that in Delphi.

 

Free Pascal has an unit of the same name and fucntion, but also supportsWriteStr(), which is available even in Delphi mode, so it is first order approx compatible with both Delphi and GPC for this.