Consider the following program:

import std.stdio;

void main(string[] args) {
    int a, b, c;
    while(true) {
        readf("%d,%d,%d", &a, &b, &c);
        writeln(a, b, c);
    }
}

If I enter "5,5,5" on the commandline, hit enter, then enter "5,5,5" a second time, hit enter again, the second time it crashes. Why? What am I getting wrong here?

The error I am getting is the following:
std.conv.ConvException@/usr/include/dmd/phobos/std/conv.d(2002): Unexpected '5' when converting from type LockingTextReader to type int
----------------
/usr/include/dmd/phobos/std/conv.d:58 int std.conv.parse!(int, std.stdio.LockingTextReader).parse(ref std.stdio.LockingTextReader) [0x440072]
/usr/include/dmd/phobos/std/conv.d:2226 int std.conv.parse!(int, std.stdio.LockingTextReader).parse(ref std.stdio.LockingTextReader, uint) [0x43fd63]
/usr/include/dmd/phobos/std/format.d:4383 int std.format.unformatValue!(int, std.stdio.LockingTextReader, char).unformatValue(ref std.stdio.LockingTextReader, ref std.format.FormatSpec!(char).FormatSpec) [0x43f529]
/usr/include/dmd/phobos/std/format.d:631 uint std.format.formattedRead!(std.stdio.LockingTextReader, char, int*, int*, int*).formattedRead(ref std.stdio.LockingTextReader, const(char)[], int*, int*, int*) [0x43a452]
/usr/include/dmd/phobos/std/stdio.d:1661 uint std.stdio.File.readf!(int*, int*, int*).readf(const(char[]), int*, int*, int*) [0x43a391]
/usr/include/dmd/phobos/std/stdio.d:3331 uint std.stdio.readf!(int*, int*, int*).readf(const(char[]), int*, int*, int*) [0x43a2a7]
source/app.d:47 _Dmain [0x43a253]
??:? _D2rt6dmain211_d_run_mainUiPPaPUAAaZiZ6runAllMFZ9__lambda1MFZv [0x44852a]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x448468]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).runAll() [0x4484e6]
??:? void rt.dmain2._d_run_main(int, char**, extern (C) int function(char[][])*).tryExec(scope void delegate()) [0x448468]
??:? _d_run_main [0x4483c5]
??:? main [0x4445f7]
??:? __libc_start_main [0xdddd2a3f]

On Thursday, 7 April 2016 at 20:42:17 UTC, default0 wrote:
> If I enter "5,5,5" on the commandline, hit enter, then enter "5,5,5"


When you hit enter, that puts a \n character in the buffer. readf doesn't skip that automatically, so it complains upon hitting that newline (the error message shows the character *after* it though, which sucks).


But what you want to do is to read whitespace too. I think putting a space in the format string at the beginning or end will do it (I don't use readf often though).

On Thursday, 7 April 2016 at 20:47:35 UTC, Adam D. Ruppe wrote:
> On Thursday, 7 April 2016 at 20:42:17 UTC, default0 wrote:
>> If I enter "5,5,5" on the commandline, hit enter, then enter "5,5,5"
>
>
> When you hit enter, that puts a \n character in the buffer. readf doesn't skip that automatically, so it complains upon hitting that newline (the error message shows the character *after* it though, which sucks).
>
>
> But what you want to do is to read whitespace too. I think putting a space in the format string at the beginning or end will do it (I don't use readf often though).

Changing the format string to "%d,%d,%d\n" fixed the problem. Would've figured if the error complained about '\n' instead of '5'.

On 04/07/2016 01:49 PM, default0 wrote:
> On Thursday, 7 April 2016 at 20:47:35 UTC, Adam D. Ruppe wrote:
>> On Thursday, 7 April 2016 at 20:42:17 UTC, default0 wrote:
>>> If I enter "5,5,5" on the commandline, hit enter, then enter "5,5,5"
>>
>>
>> When you hit enter, that puts a \n character in the buffer. readf
>> doesn't skip that automatically, so it complains upon hitting that
>> newline (the error message shows the character *after* it though,
>> which sucks).
>>
>>
>> But what you want to do is to read whitespace too. I think putting a
>> space in the format string at the beginning or end will do it (I don't
>> use readf often though).
>
> Changing the format string to "%d,%d,%d\n" fixed the problem. Would've
> figured if the error complained about '\n' instead of '5'.

Which compiler version? This is fixed:

  https://issues.dlang.org/show_bug.cgi?id=15695

It's now better but \n may be hard to decode from the following message:

std.conv.ConvException@/usr/include/dmd/phobos/std/conv.d(2002): Unexpected '
' when converting from type LockingTextReader to type int

Ali

On Thursday, 7 April 2016 at 21:22:19 UTC, Ali Çehreli wrote:
> On 04/07/2016 01:49 PM, default0 wrote:
>> On Thursday, 7 April 2016 at 20:47:35 UTC, Adam D. Ruppe wrote:
>>> On Thursday, 7 April 2016 at 20:42:17 UTC, default0 wrote:
>>>> If I enter "5,5,5" on the commandline, hit enter, then enter "5,5,5"
>>>
>>>
>>> When you hit enter, that puts a \n character in the buffer. readf
>>> doesn't skip that automatically, so it complains upon hitting that
>>> newline (the error message shows the character *after* it though,
>>> which sucks).
>>>
>>>
>>> But what you want to do is to read whitespace too. I think putting a
>>> space in the format string at the beginning or end will do it (I don't
>>> use readf often though).
>>
>> Changing the format string to "%d,%d,%d\n" fixed the problem. Would've
>> figured if the error complained about '\n' instead of '5'.
>
> Which compiler version? This is fixed:
>
>   https://issues.dlang.org/show_bug.cgi?id=15695
>
> It's now better but \n may be hard to decode from the following message:
>
> std.conv.ConvException@/usr/include/dmd/phobos/std/conv.d(2002): Unexpected '
> ' when converting from type LockingTextReader to type int
>
> Ali

dmd --version prints out 2.070.2

I believe 2.071 is the most recent version?

On 04/07/2016 07:56 PM, default0 wrote:

> dmd --version prints out 2.070.2
>
> I believe 2.071 is the most recent version?

Yes, that's fresh out of the oven :) with potentially confusing but more correct import behaviour:

  http://forum.dlang.org/thread/ne1fd0$1r10$1@digitalmars.com

Ali