• Friedrich Dominicus (12/12) Aug 19 2003 What is the D way for a generic print function?
• Ilya Minkov (19/30) Aug 19 2003 D is not dynamically typed, and hence ints and other simple types are
• Helmut Leitner (28/32) Aug 22 2003 You can find my try at this in the Venus library:

Friedrich Dominicus <frido q-software-solutions.com> writes:

What is the D way for a generic print function?
As I tried the base types like int are not of type object.
e.g I can not use toString on an int.

Is there a way to find out to find out which type a variable has 
something like

type_of (var) == int of the like?

Of is there another recommended way to promote a base type to an char[]?
I could use something line sprintf, but for that I have to knw the type 
of some variable. So could someone give me a hand on how to do it
the D way?

Regards
Friedrich

Ilya Minkov <midiclub 8ung.at> writes:

Friedrich Dominicus wrote:
 What is the D way for a generic print function?
 As I tried the base types like int are not of type object.
 e.g I can not use toString on an int.

Looks like an omission. :)

 Is there a way to find out to find out which type a variable has 
 something like
 
 type_of (var) == int of the like?

D is not dynamically typed, and hence ints and other simple types are 
simply the type you declare them with in current scope. For classes, 
there is a way to get (a real ton of) type information, it's implemented 
but not documented yet. Burton even wrote an automatic serialisation 
library based on it.

You can distinguish a type when calling a function by overloading a 
function for multiple input types.

Yet another way is to imitate variant/dynamic typing. You create a 
struct which acts as a smart (discriminated) union, which can hold 
strings, integers, objects, and so on. Then you define conversion 
constructors for all types it needs to input, and this thingy is a basis 
for a typesafe printf, which is not in the standard library, but has 
been implemented elsewhere.

 Of is there another recommended way to promote a base type to an char[]?
 I could use something line sprintf, but for that I have to knw the type 
 of some variable. So could someone give me a hand on how to do it
 the D way?

There are a number of "what may become D way" libraries in development, 
all scattered around different places. I think i shall go search through 
the newsgroup and collect them all on Helmut's WIKI.

-eye

Helmut Leitner <helmut.leitner chello.at> writes:

Friedrich Dominicus wrote:
 
 What is the D way for a generic print function?
 As I tried the base types like int are not of type object.
 e.g I can not use toString on an int.

You can find my try at this in the Venus library:
  <http://www.wikiservice.at/wiki4d/wiki.cgi?VenusLibrary>
Basically in the modules:
  - print.d (who solves the concrete problem)
  - type.d (basics for similar generic primitive interfaces)

In fact dmd 0.68 should have paved the path to make things
simpler, because primitives now provide a .typeinfo property

   long l;
   TypeInfo ti=l.typeinfo;

while I had to fake this by the TypeMethods structure and
a overloaded TypeRetTpi.

So this could be reworked. The standard .typeinfo (TypeInfo) 
structure could be extended with the functions of type.d 
(TypeMethods) basically for 
       string->type
       type->string 
       string->type (options)
       type->string (formatting)
    conversions. 

This should simplefy things a lot to generate "generic" functions for
primitive ryoe and reduce the code to less then half of the current 
LOC count.

But I hadn't yet the time to do the preparations and suggest 
this to Walter in a proper way.

--
Helmut Leitner    leitner hls.via.at   
Graz, Austria   www.hls-software.com