Proper usage of templates

**Sebastiani** · 07-26-2009

Well, the problem isn't what you're passing to it, but what it returns.

**Kudose** · 07-26-2009

Originally Posted by Sebastiani

Well, the problem isn't what you're passing to it, but what it returns.

I see that based on sqrt - C++ Reference

It only returns float or double types.

Code:

#include <iostream>
#include <string>
#include <math.h>

using namespace std;

template<class T> T inner_product(const T &a, const T &b){
  return a * a + b * b;
}

template<class T> T squareroot(const T &c){
  return sqrt(c);
}

template<class T> T pythagorean(const T &a, const T &b){
  return static_cast<T>(squareroot(inner_product(a, b)));
}

int main(){

  int a = 2, b = 4;
  double c = 10, d = 3;
  string string1 = "This is a test.";
  string string2 = "This is another test with more characters.";

  cout << pythagorean(a, b)
       << endl << pythagorean(c, d)
       << endl << pythagorean(string1.size(), string2.size());

  return 0;
}

**Kudose** · 07-26-2009

Should I be using Code::Blocks if it didn't report that warning?

**Sebastiani** · 07-26-2009

Code::Blocks is just an IDE. What version of GCC are you running?

**Kudose** · 07-26-2009

I'm not sure how to tell ... it is the default GNU GCC compiler Code::Blocks uses.

**Sebastiani** · 07-26-2009

>> I'm not sure how to tell ... it is the default GNU GCC compiler Code::Blocks uses.

You IDE users are hilarious. Open up a command prompt and type:

g++ --version [ENTER]

If you don't get a response you'll need to navigate to the Code::Blocks bin directory (unless you have GCC installed somewhere else, of course, in which case you can just search your drive for g++.exe).

**Kudose** · 07-26-2009

g++ (GCC) 2.4.5 (mingw-vista special)

**Sebastiani** · 07-26-2009

>> g++ (GCC) 2.4.5 (mingw-vista special)

Oh man, you are seriously out of date. That was released back in '93!

**Kudose** · 07-26-2009

My linux server reports it correctly though, but doesn't seem to like quotes ...

Code:

root@server [~]# g++ -o pythag pythag.cpp
pythag.cpp: In function âT squareroot(const T&) [with T = int]â:
pythag.cpp:16:   instantiated from âT pythagorean(const T&, const T&) [with T = int]â
pythag.cpp:26:   instantiated from here
pythag.cpp:12: warning: converting to âintâ from âdoubleâ
pythag.cpp: In function âT squareroot(const T&) [with T = long unsigned int]â:
pythag.cpp:16:   instantiated from âT pythagorean(const T&, const T&) [with T = size_t]â
pythag.cpp:28:   instantiated from here
pythag.cpp:12: warning: converting to âlong unsigned intâ from âdoubleâ
root@server [~]# g++ --version
g++ (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

**Kudose** · 07-26-2009

Originally Posted by Sebastiani

>> g++ (GCC) 2.4.5 (mingw-vista special)

Oh man, you are seriously out of date. That was realeased back in '93!

Ok, it has a bunch of compiler options, so I should be able to find a newer one in there.

**Sebastiani** · 07-26-2009

Here is the latest version of the mingw compiler. Just be sure to either make a copy of the existing GCC directory or install it in a new one.

**Kudose** · 07-26-2009

I think I am going to use a different IDE ... changing any options in Code::Blocks eats up 50% of all 4 of my processor cores and takes 5 seconds to open. Also, after I changed the compiler I can no longer get the project to run ... it builds and shows the errors though.

**Kudose** · 07-26-2009

Originally Posted by Sebastiani

Here is the latest version of the mingw compiler. Just be sure to either make a copy of the existing GCC directory or install it in a new one.

Thanks, I'll give that a shot before I abandon Code::Blocks.

**Sebastiani** · 07-26-2009

>> Thanks, I'll give that a shot before I abandon Code::Blocks.

You don't have to use another IDE!

Just unzip the mingw file into a directory and then go to your IDE's compiler options and set it up to use the new compiler (I've never used that IDE so I don't know what the exact process is, though). Alternately, just make a copy of the old GCC directory as a backup, and then replace it with the new one, but keep the directory name and structure the same. That way, you don't even have to "tell" Code::Blocks - it will just assume that it's using the same compiler.

**Sebastiani** · 07-26-2009

>> I think I am going to use a different IDE ... changing any options in Code::Blocks eats up 50% of all 4 of my processor cores and takes 5 seconds to open. Also, after I changed the compiler I can no longer get the project to run ... it builds and shows the errors though.

Oh, ok I missed that post. Well, I don't use an IDE and I really can't think of one off the top of my head. Dev-C++ *was* supposedly pretty decent, but I think the project's been since abandoned. Oh well, I'm sure someone here will have a good suggestion for you.

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