🚀 go-pugleaf

acinader@panix.com (Arthur Cinader Jr) wrote:

>I may be going at this wrong, but I want to have a class
>Triangle contain a static method called makeinstance.  The
>method will be passed a refernce to a Param object that has
>a list of parameters for checking first and then passing to 
>the Triangle constructor.

>The parameters are checked and if all is ok, a Triangle
>instance is "newed" and the pointer to the new Trinagle is
>returned.  When I compile, I get the following error:

>% g++ -c triangle.C
>In file included from triangle.C:8:
>triangle.h:17: syntax error before `*'
>...
>%

>***The declaration for the class:

>      1 // triangle.h
>      2 // declaration of class Triangle extends shape
>      3
>      4 #ifndef TRIANGLE_H
>      5 #define TRIANGLE_H
>      6
>      7 #include "point.h"
>      8 #include "param.h"
>      9
>     10 class Trianlge : public Point {
>     11 public:
>     12     Trinagle(float = 0.0, float = 0.0, float = 0.0);
>     13     float gets() const;
>     14     virtual void draw() const;
>     15
>     16     static Param &getParams();
>     17     static Triangle *makeinstance(Param &);
>     18 private:
>     19     float side;
>     20 };
>     21
>     22 #endif

The idea looks fine to me. However, if this is a direct copy of the code you
wrote you better mind your spelling. The word Triangle is spelled differently in
the three place it appears:

class Trianlge...

Trinagle(float....

static Triangle *makeinstance...

This would definitely cause the problem you described...

--
Noel Fegan
European Software Development Department
American Power Conversion
My views used to be my own, and then I got married...
I don't speak for APC...
nfegan@apcc.com

Arthur Cinader Jr (acinader@panix.com) wrote:

> The parameters are checked and if all is ok, a Triangle
> instance is "newed" and the pointer to the new Trinagle is
> returned.  When I compile, I get the following error:

> % g++ -c triangle.C
> In file included from triangle.C:8:
> triangle.h:17: syntax error before `*'
> ...
> %

> ***The declaration for the class:

[...]

>      10 class Trianlge : public Point {
		^^^^^^^^
If you included the exact code, the above typo may be the culprit.

And IMHO, I think a Triangle is not "is-a" Point but rather it is 
composed of points.  So I think Triangle should not inherit from Point.
Just a thought.

Shekar

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In article <4hdu70$efa@panix.com>, acinader@panix.com (Arthur Cinader Jr) writes:

>     10 class Trianlge : public Point {
                    ^^   Tri - a n g l e 

>     11 public:
>     12     Trinagle(float = 0.0, float = 0.0, float = 0.0);
                ^^


>     13     float gets() const;
>     14     virtual void draw() const;
>     15
>     16     static Param &getParams();
>     17     static Triangle *makeinstance(Param &);
                    ^^^^^^^^ This is the traditional spelling

>     18 private:
>     19     float side;
>     20 };

Trianlge, Trianagle, Triangle: pick one, and stick with it ;)
 ---
 Mickey Williams
 Ericsson Inc.            Business Systems Division
 +1 714 236-6753
 The opinions above are mine alone, and not those of my employer...
 

Thanks to all who pointed out my typos!  I swear I checked for
them and evenb after they were pointed out, I still had to
hunt for them....?

Guess I need glasses...

Arthur

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At line 10, surely Trianlge should be Triangle?

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From: acinader@panix.com (Arthur Cinader Jr)
Newsgroups: gnu.g++.help,comp.lang.c++
Subject: IS THIS LEGAL? Static method returns pointer to class
Date: 4 Mar 1996 00:14:08 -0500
Organization: Panix
Message-ID: <4hdu70$efa@panix.com>

I may be going at this wrong, but I want to have a class
Triangle contain a static method called makeinstance.  The
method will be passed a refernce to a Param object that has
a list of parameters for checking first and then passing to 
the Triangle constructor.

The parameters are checked and if all is ok, a Triangle
instance is "newed" and the pointer to the new Trinagle is
returned.  When I compile, I get the following error:

% g++ -c triangle.C
In file included from triangle.C:8:
triangle.h:17: syntax error before `*'
..
%

***The declaration for the class:

      1 // triangle.h
      2 // declaration of class Triangle extends shape
      3
      4 #ifndef TRIANGLE_H
      5 #define TRIANGLE_H
      6
      7 #include "point.h"
      8 #include "param.h"
      9
     10 class Trianlge : public Point {
     11 public:
     12     Trinagle(float = 0.0, float = 0.0, float = 0.0);
     13     float gets() const;
     14     virtual void draw() const;
     15
     16     static Param &getParams();
     17     static Triangle *makeinstance(Param &);
     18 private:
     19     float side;
     20 };
     21
     22 #endif

---------------------------------19997724768799091920253434--

In article <Dnt85t.FGu@doc.ntu.ac.uk>, pt3chaj says...
[SNIP!!]
>     17     static Triangle *makeinstance(Param &);
[snip!--a smaller snip ;-))

Drop the * before the function name--what you have here is a pointer to a 
function (which is itself a pointer...)

It should work fine if you just define it at:

	static Triangle makeinstance(Param &);

I've used static functions to create objects, especially singletons, a la 
Design Patterns--Gamma, et al.

Works like a charm...
-- 
G. Patrick Sand
psand@eos.hitc.com
PatSand@aol.com
(301) 925-0791
"Travel Light But Right..."
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