• James Dunne (19/19) Apr 01 2005 How do I inherit a template class?
• Andrew Fedoniouk (16/39) Apr 01 2005 Should be written as

James Dunne <jdunne4 bradley.edu> writes:

How do I inherit a template class?

I have code like this:

// Define templated Vector class:
class Vector(alias type, int size) {
..
}

// Inherit the Vector class to create a Point3D class:
class Point3D : Vector!(float, 3) {
..
}

The compiler reports on the definition of class Point3D line with this error:
"template instance Vector!(float,3) does not match any template declaration"

If I try to inherit Vector with no template arguments, the compiler reports on
the same line with this error:
"template dts_point.Vector(alias type,int size) is used as a type"


It seems that D's template system is either missing some of C++'s template
features, or is not documenting how to achieve equal functionality.

Regards,
James Dunne

"Andrew Fedoniouk" <news terrainformatica.com> writes:

Your declaration

 class Vector(alias type, int size) {

Should be written as
    class Vector(type, int size) ....

Please read
http://www.digitalmars.com/d/template.html

for the meaning of word 'alias' in template declarations.

In short 'alias'ed paramater in D template is not a name of a class 
(typename) but
alias of some object.  And you are right - there is no direct C++ equivalent 
for that.

Take a look on Ben's examples:
http://home.comcast.net/~benhinkle/mintl/

Andrew.
http://terrainformatica.com



"James Dunne" <jdunne4 bradley.edu> wrote in message 
news:d2kmrt$1rnp$1 digitaldaemon.com...
 How do I inherit a template class?

 I have code like this:

 // Define templated Vector class:
 class Vector(alias type, int size) {
 ..
 }

 // Inherit the Vector class to create a Point3D class:
 class Point3D : Vector!(float, 3) {
 ..
 }

 The compiler reports on the definition of class Point3D line with this 
 error:
 "template instance Vector!(float,3) does not match any template 
 declaration"

 If I try to inherit Vector with no template arguments, the compiler 
 reports on
 the same line with this error:
 "template dts_point.Vector(alias type,int size) is used as a type"


 It seems that D's template system is either missing some of C++'s template
 features, or is not documenting how to achieve equal functionality.

 Regards,
 James Dunne