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Talk:Generic swap: Difference between revisions
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added a section header to the first topic to properly place the table-of-contents (TOC) --- (this happens more often than one would think).
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== task description too language-specific? ==
This task description seems to me a little too language-specific in its concepts.
Line 18 ⟶ 20:
--[[User:Kevin Reid|Kevin Reid]] 21:41, 7 September 2007 (EDT)
I do not want to limit the implementation. I am after the abstract functionality. I chose "swap" because it is conceptually simple. I am more interested in demonstrating genericity than the low level nature of swap.
--[[Waldorf|Waldorf]] 20:27, 7 September 2007 (MDT)
== C++ ==
Would the C++ example here assume that there is a copy constructor for T types? Would it be better to have "tmp = left" rather than "tmp(left)"? --[[User:mwn3d|mwn3d]] 00:08, 14 November 2007
: Well, in some circumstances (assigning a char to a CString in Windows MFC, for example), you ''have'' to use the explicit constructor, due to the way a class was defined. Granted, it would be a poor class implementation that required explicit use of its own copy constructor, but it's not impossible.
:
: In addition, I tried a couple small programs to test the problem:
<pre>#include <iostream>
using namespace std;
int main()
{
int a = 7;
int b = int(a);
cout << b << endl;
}
</pre>
: This outputs "7".
:
: I also tried creating a class with no defined copy constructor:
<pre>#include <iostream>
using namespace std;
class CNoCopy
{
public:
int m_value;
CNoCopy()
{
cout << "Constructor Called" << endl;
}
~CNoCopy()
{
cout << "Destructor called" << endl;
}
void setValue( int newVal )
{
m_value = newVal;
}
int getValue()
{
return m_value;
}
};
int main()
{
CNoCopy o1;
o1.setValue( 7 );
CNoCopy o2 = CNoCopy( o1 );
cout << o2.getValue() << endl;
}
</pre>
:This outputs
<pre>Constructor Called
7
Destructor called
Destructor called
</pre>
: So the copy went ahead, without calling any explicitly-define constructor. For reference, I'm using [[G++]] 4.1.3. In all, I think the implementation is fine. --[[User:Short Circuit|Short Circuit]] 19:06, 14 November 2007 (MST)
== boolga boolga boolga ==
y does the c version use char* and not void *? can it use anything? long* int* short* byte*etc?
:Because you can't operate on (void *), only refer to it. That said, a ''real'' implementation would cast to (int *) first (the most efficient machine word size), then finish any leftovers with a few less efficient (char *) swaps at the end. --[[User:IanOsgood|IanOsgood]] 18:50, 3 February 2008 (MST)
== dc ==
reverse is only available as a GNU extension (same with n, and comments (#) etc. - probably the other version should be kept too?)
[[User:Rahul|Rahul]] 20:46, 8 December 2008 (UTC)
: OK. Could you link (or simply list; dc is tiny) the standard dc commands on the language page? --[[User:IanOsgood|IanOsgood]] 02:02, 9 December 2008 (UTC)
:: I will add the list of commands to the dc page. [[User:Rahul|Rahul]] 09:13, 9 December 2008 (UTC)
AFIK, dc only has a single data type (numeric value), so how is it '''generic''' swap? --[[User:PauliKL|PauliKL]] 12:52, 9 December 2008 (UTC)
: Would be an interesting question, because since unityped systems are a subset of typed systems. So it can be argued that if dc is unityped, then all the procedures that it implements are generic by default. Interestingly dc is not unityped -
i.e
$dc
[ 1 2 3 4 ]
[ 5 6 7 8 ]
sa sb la lb
f
1 2 3 4
5 6 7 8
[[User:Rahul|Rahul]] 13:47, 9 December 2008 (UTC)
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