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digitalmars.D.learn - Why toUTF8 not accept wchar[] as argument?

reply Domain <dont_email empty.com> writes:
wchar[10] buffer;
toUTF8(buffer);

Error: template `std.utf.toUTF8` cannot deduce function from 
argument types `!()(wchar[10])`, candidates are:
/dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):        
`std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S && 
isSomeChar!(ElementEncodingType!S))`


I know buffer.idup is OK. But why? That's very inconvenient.
Apr 02 2018
parent reply Uknown <sireeshkodali1 gmail.com> writes:
On Tuesday, 3 April 2018 at 02:24:08 UTC, Domain wrote:

 wchar[10] buffer;
 toUTF8(buffer);

 Error: template `std.utf.toUTF8` cannot deduce function from 
 argument types `!()(wchar[10])`, candidates are:
 /dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):        
 `std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S && 
 isSomeChar!(ElementEncodingType!S))`


 I know buffer.idup is OK. But why? That's very inconvenient.


What you need to do is slice your buffer. So your call will 
become like this:

---
toUTF8(buffer[]);
---

Now it will work as expected.
Apr 02 2018
next sibling parent Uknown <sireeshkodali1 gmail.com> writes:
On Tuesday, 3 April 2018 at 02:31:15 UTC, Uknown wrote:

 On Tuesday, 3 April 2018 at 02:24:08 UTC, Domain wrote:

 wchar[10] buffer;
 toUTF8(buffer);

 Error: template `std.utf.toUTF8` cannot deduce function from 
 argument types `!()(wchar[10])`, candidates are:
 /dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):
  `std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S 
 && isSomeChar!(ElementEncodingType!S))`


 I know buffer.idup is OK. But why? That's very inconvenient.


 What you need to do is slice your buffer. So your call will 
 become like this:

 ---
 toUTF8(buffer[]);
 ---

 Now it will work as expected.


I should mention that you need to slice any static array when 
passing to functions that expect ranges
Apr 02 2018
prev sibling parent reply Domain <dont_email empty.com> writes:
On Tuesday, 3 April 2018 at 02:31:15 UTC, Uknown wrote:

 On Tuesday, 3 April 2018 at 02:24:08 UTC, Domain wrote:

 wchar[10] buffer;
 toUTF8(buffer);

 Error: template `std.utf.toUTF8` cannot deduce function from 
 argument types `!()(wchar[10])`, candidates are:
 /dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):
  `std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S 
 && isSomeChar!(ElementEncodingType!S))`


 I know buffer.idup is OK. But why? That's very inconvenient.


 What you need to do is slice your buffer. So your call will 
 become like this:

 ---
 toUTF8(buffer[]);
 ---

 Now it will work as expected.


I see. Maybe the error message could be improved.
Apr 02 2018
next sibling parent bauss <jj_1337 live.dk> writes:
On Tuesday, 3 April 2018 at 02:46:51 UTC, Domain wrote:

 On Tuesday, 3 April 2018 at 02:31:15 UTC, Uknown wrote:

 On Tuesday, 3 April 2018 at 02:24:08 UTC, Domain wrote:

 wchar[10] buffer;
 toUTF8(buffer);

 Error: template `std.utf.toUTF8` cannot deduce function from 
 argument types `!()(wchar[10])`, candidates are:
 /dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):
  `std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S 
 && isSomeChar!(ElementEncodingType!S))`


 I know buffer.idup is OK. But why? That's very inconvenient.


 What you need to do is slice your buffer. So your call will 
 become like this:

 ---
 toUTF8(buffer[]);
 ---

 Now it will work as expected.


 I see. Maybe the error message could be improved.


Well depends. The error message is correct and if you took a look 
at each constraint you'd understand it.

Once you understand that static arrays don't work with functions 
expecting ranges, then it kinda becomes common sense as to why it 
doesn't work.
Apr 02 2018
prev sibling parent reply Seb <seb wilzba.ch> writes:
On Tuesday, 3 April 2018 at 02:46:51 UTC, Domain wrote:

 On Tuesday, 3 April 2018 at 02:31:15 UTC, Uknown wrote:

 On Tuesday, 3 April 2018 at 02:24:08 UTC, Domain wrote:

 wchar[10] buffer;
 toUTF8(buffer);

 Error: template `std.utf.toUTF8` cannot deduce function from 
 argument types `!()(wchar[10])`, candidates are:
 /dlang/dmd/linux/bin64/../../src/phobos/std/utf.d(2713):
  `std.utf.toUTF8(S)(S s) if (isInputRange!S && !isInfinite!S 
 && isSomeChar!(ElementEncodingType!S))`


 I know buffer.idup is OK. But why? That's very inconvenient.


 What you need to do is slice your buffer. So your call will 
 become like this:

 ---
 toUTF8(buffer[]);
 ---

 Now it will work as expected.


 I see. Maybe the error message could be improved.


Yep, I opened an enhancement request for you: 
https://issues.dlang.org/show_bug.cgi?id=18711

Better diagnostics and error messages is a key goal in 2018 for 
dmd ;-)
Apr 02 2018
parent reply Timoses <timosesu gmail.com> writes:
On Tuesday, 3 April 2018 at 05:20:55 UTC, Seb wrote:

 Better diagnostics and error messages is a key goal in 2018 for 
 dmd ;-)


Awesome! How about telling the user which of the template 
constraints failed? Would be so awesome. Currently, there's a 
need to check every single one (as mentioned by bauss) which can 
sometimes be a hassle.
Apr 03 2018
parent Timoses <timosesu gmail.com> writes:
On Tuesday, 3 April 2018 at 13:12:05 UTC, Timoses wrote:

 On Tuesday, 3 April 2018 at 05:20:55 UTC, Seb wrote:

 Better diagnostics and error messages is a key goal in 2018 
 for dmd ;-)


 Awesome! How about telling the user which of the template 
 constraints failed? Would be so awesome. Currently, there's a 
 need to check every single one (as mentioned by bauss) which 
 can sometimes be a hassle.


I guess related issues are:
https://issues.dlang.org/show_bug.cgi?id=9626
https://issues.dlang.org/show_bug.cgi?id=4970
Apr 03 2018