Re: Main foreach loop fails when another foreach is added

[ikelaiah via Digitalmars-d-learn]

On Monday, 8 August 2022 at 02:45:54 UTC, Steven Schveighoffer 
wrote:


And now, you tried to read it again! Which means you are trying 
to read more data from an empty stream.


You need to either a) reopen the file, or b) do both in the 
same loop.



-Steve


Steve! You are Legend!
**Thank you**.
It is obvious now the second `foreach` is reading from an empty 
stream!


Regards,
ikel

Re: Main foreach loop fails when another foreach is added

[Steven Schveighoffer via Digitalmars-d-learn]

On 8/7/22 10:11 PM, ikelaiah wrote:

Hi,

I'm writing a program that reads a text file and launch my work URLs in it.
It worked fine, and very happy.

Then I added another `foreach` loop to count total number of lines.
After this, the main `foreach` won't work.

Does anyone know as to why this happens?
I might have missed something very obvious.

Thank you.




```d


...


     // Open input file for reading
     size_t line_count = 0;
     File input_file = File(input_filename);


Here you open the file

     auto file_range = input_file.byLine(KeepTerminator.no, 
std.ascii.newline);


And then wrap it in a byline range.



     // if this foreach not commented out
     // the last foreach won't run.
     foreach (char[] line; file_range)
     {
     line_count += 1;
     }


For this foreach loop, you read every line in the file, exhausting the 
file (the input stream for the file is empty).




     // the MAIN foreach loop
     // -- won't run if above foreach is enabled
     foreach (char[] line; file_range)
     {
     if (!line.empty)
     {
     writeln("Open URL: " ~ line);
     Thread.sleep(dur!("seconds")(2));
     browse(line);
     }
     }


And now, you tried to read it again! Which means you are trying to read 
more data from an empty stream.


You need to either a) reopen the file, or b) do both in the same loop.


```


-Steve

Main foreach loop fails when another foreach is added

[ikelaiah via Digitalmars-d-learn]

Hi,

I'm writing a program that reads a text file and launch my work 
URLs in it.

It worked fine, and very happy.

Then I added another `foreach` loop to count total number of 
lines.

After this, the main `foreach` won't work.

Does anyone know as to why this happens?
I might have missed something very obvious.

Thank you.

Regards,
ikel


```d
module openurls;

import std.stdio : writeln, File, KeepTerminator;
import std.file;
import std.range;
import std.ascii;
import std.getopt : getopt, GetoptResult, defaultGetoptPrinter;
import std.process : browse;
import core.thread.osthread;
import core.time;


void main(string[] args)
{
string input_filename = "";

// Get command line option
GetoptResult user_args = getopt(args,
"input|i", "A list of URLs separated by new lines.", 
_filename);


// Does user need help?
if (user_args.helpWanted)
{
defaultGetoptPrinter("Command line options for Open 
URLs.",

user_args.options);
}

// Is input file specified?
if (input_filename.length == 0)
{
writeln("Open URL: No file specified.\n");
defaultGetoptPrinter("Command line option for Open URLs.",
user_args.options);
return;
}

// Does the file exist?
if (!input_filename.exists)
{
writeln("Open URL: input file --" ~ input_filename ~ "-- 
does not exist.\n");

return;
}
else
{
writeln("Open URL: reading --" ~ input_filename ~ "--");
}

// Open input file for reading
size_t line_count = 0;
File input_file = File(input_filename);
auto file_range = input_file.byLine(KeepTerminator.no, 
std.ascii.newline);


// if this foreach not commented out
// the last foreach won't run.
foreach (char[] line; file_range)
{
line_count += 1;
}

// the MAIN foreach loop
// -- won't run if above foreach is enabled
foreach (char[] line; file_range)
{
if (!line.empty)
{
writeln("Open URL: " ~ line);
Thread.sleep(dur!("seconds")(2));
browse(line);
}
}

writeln("Open URL: completed");

writeln("Closing " ~ input_filename);
input_file.close();
}

```