• Andy Balba (16/16) Jul 29 2020 The following example taken from
• Steven Schveighoffer (4/25) Jul 29 2020 Are you importing std.algorithm.comparison?
• Seb (8/24) Jul 29 2020 Your release of GDC seems to use a very old version of Phobos.

Andy Balba <pwplus7 gmail.com> writes:

The following example taken from 
https://dlang.org/library/std/algorithm/comparison/pred_switch.html

doesn't compile under gdc...Is there a way to fix it ?


int factorial(int n)
{
     return n.predSwitch!"a <= b"(
         -1, {throw new Exception("Can not calculate n! for n < 
0");}(),
         0, 1, // 0! = 1
         n * factorial(n - 1) // n! = n * (n - 1)! for n >= 0
         );
}
writeln(factorial(3));

The gdc compiler error is
  error: no property 'predSwitch' for type 'int'
      return n.predSwitch!"a <= b"(

Steven Schveighoffer <schveiguy gmail.com> writes:

On 7/29/20 5:46 PM, Andy Balba wrote:
 
 The following example taken from 
 https://dlang.org/library/std/algorithm/comparison/pred_switch.html
 
 doesn't compile under gdc...Is there a way to fix it ?
 
 
 int factorial(int n)
 {
      return n.predSwitch!"a <= b"(
          -1, {throw new Exception("Can not calculate n! for n < 0");}(),
          0, 1, // 0! = 1
          n * factorial(n - 1) // n! = n * (n - 1)! for n >= 0
          );
 }
 writeln(factorial(3));
 
 The gdc compiler error is
   error: no property 'predSwitch' for type 'int'
       return n.predSwitch!"a <= b"(
 

Are you importing std.algorithm.comparison?

This kind of question probably belongs on the learn forum.

-Steve

Seb <seb wilzba.ch> writes:

On Wednesday, 29 July 2020 at 21:46:04 UTC, Andy Balba wrote:
 The following example taken from 
 https://dlang.org/library/std/algorithm/comparison/pred_switch.html

 doesn't compile under gdc...Is there a way to fix it ?


 int factorial(int n)
 {
     return n.predSwitch!"a <= b"(
         -1, {throw new Exception("Can not calculate n! for n < 
 0");}(),
         0, 1, // 0! = 1
         n * factorial(n - 1) // n! = n * (n - 1)! for n >= 0
         );
 }
 writeln(factorial(3));

 The gdc compiler error is
  error: no property 'predSwitch' for type 'int'
      return n.predSwitch!"a <= b"(

Your release of GDC seems to use a very old version of Phobos.
You need to have Phobos >= 2.067 (released in 2015) for this to 
work, see e.g. https://run.dlang.io/is/cAFJoB
On Ubuntu/Debian you should be able to at least get a GDC 
libphobos of 2.076.

Alternatively, as you might expect it works in dmd or ldc: 
https://run.dlang.io/is/CpFfkQ