• nrgyzer <nrgyzer gmail.com> May 30 2012
• "bearophile" <bearophileHUGS lycos.com> May 30 2012
• nrgyzer <nrgyzer gmail.com> May 30 2012
• "bearophile" <bearophileHUGS lycos.com> May 30 2012
• Artur Skawina <art.08.09 gmail.com> May 30 2012

nrgyzer <nrgyzer gmail.com> writes:

Hi,

I've the following enumeration:

enum path : string {

  log1 = "/var/log1",
  log2 = "/var/log2"

}

Now... when I try to do the following:

string subDirectory = "example";

string newPath = buildPath(path.log1, subDirectory);

I get the following errors:

Error: template std.path.buildPath does not match any function template
declaration
Error: template std.path.buildPath(C) if (isSomeChar!(C)) cannot deduce
template function from argument types !()(path,string)
Error: template std.path.buildPath does not match any function template
declaration
Error: template std.path.buildPath(C) if (isSomeChar!(C)) cannot deduce
template function from argument types !()(path,string)

Is this a bug in std.path.buildPath() or is there anything I'm doing wrong?

"bearophile" <bearophileHUGS lycos.com> writes:

nrgyzer:

 Is this a bug in std.path.buildPath() or is there anything I'm 
 doing wrong?


The signature of buildPath is:

immutable(C)[] buildPath(C)(const(C[])[] paths...);

But your inputs aren't of the same type. Named enum create their 
own type. You give buildPath a type string and a type path, that 
is not a string.

There are various solutions, this compiles, but it's not very 
safe:

buildPath(cast(string)path.log1, subDirectory);

Another solution is to not use a named enum:

enum : string {
     path_log1 = "/var/log1",
     path_log2 = "/var/log2"
}

buildPath(path_log1, subDirectory)

In bugzilla I have asked for an enum property that returns the 
raw value&type of an enum.

Bye,
bearophile

nrgyzer <nrgyzer gmail.com> writes:

== Auszug aus bearophile (bearophileHUGS lycos.com)'s Artikel
 nrgyzer:
 Is this a bug in std.path.buildPath() or is there anything I'm
 doing wrong?


 immutable(C)[] buildPath(C)(const(C[])[] paths...);
 But your inputs aren't of the same type. Named enum create their
 own type. You give buildPath a type string and a type path, that
 is not a string.
 There are various solutions, this compiles, but it's not very
 safe:
 buildPath(cast(string)path.log1, subDirectory);
 Another solution is to not use a named enum:
 enum : string {
      path_log1 = "/var/log1",
      path_log2 = "/var/log2"
 }
 buildPath(path_log1, subDirectory)
 In bugzilla I have asked for an enum property that returns the
 raw value&type of an enum.
 Bye,
 bearophile


Alright, thanks... but I want to do the following:

foreach(c; __traits(allMembers, path))
 if (!exists(mixin("path." ~ c))) mkdirRecurse(mixin("path." ~ c));

When I use a named enum, I can't use the source above... so I've to cast in the
buildPath()-method to my path enumeration or is there any other chance to
realize the foreach-loop?

"bearophile" <bearophileHUGS lycos.com> writes:

A better solution is to use:

struct Path {
     enum : string {
         log1 = "/var/log1",
         log2 = "/var/log2"
     }
}


Or even just:

struct Path {
     enum string log1 = "/var/log1",
                 log2 = "/var/log2";
}

(In D structs, classes and enums start with an upper case).

Bye,
bearophile

Artur Skawina <art.08.09 gmail.com> writes:

On 05/30/12 20:34, nrgyzer wrote:
 Hi,
 
 I've the following enumeration:
 
 enum path : string {
 
   log1 = "/var/log1",
   log2 = "/var/log2"
 
 }
 
 Now... when I try to do the following:
 
 string subDirectory = "example";
 
 string newPath = buildPath(path.log1, subDirectory);
 
 I get the following errors:
 
 Error: template std.path.buildPath does not match any function template
 declaration
 Error: template std.path.buildPath(C) if (isSomeChar!(C)) cannot deduce
 template function from argument types !()(path,string)
 Error: template std.path.buildPath does not match any function template
 declaration
 Error: template std.path.buildPath(C) if (isSomeChar!(C)) cannot deduce
 template function from argument types !()(path,string)
 
 Is this a bug in std.path.buildPath() or is there anything I'm doing wrong?
 


A bug, as an enum member is supposed to implicitly convert to its base type. [1]

You might be able to work-around it like this

   template _path() {
      enum : string {
        log1 = "/var/log1",
        log2 = "/var/log2"
      }
   }
   alias _path!() path;

artur

[1] Actually, D's "typesafe variadic functions" don't play well with certain
other features too, eg

   void f(A...)(A a) {}
   void f()(string[] a...) {}
   f("a", "b"); // expecting the second overload to be called is reasonable,
                // but this isn't what's going to happen.