Re: How do you make a copy TO and object when you're INSIDE of it?
Apart from what others have said, for a class `this` is the _reference_ to the current object, i.e. a pointer. If the compiler allowed assigning to it, it would not modify the contents of your object. If you want to assign all of the elements at once, you can use `tupleof` (untested): this.tupleof = other.tupleof;
Re: How do you make a copy TO and object when you're INSIDE of it?
On Friday, 24 July 2015 at 14:12:54 UTC, Steven Schveighoffer wrote: On 7/24/15 4:47 AM, Marc =?UTF-8?B?U2Now7x0eiI=?= schue...@gmx.net wrote: Apart from what others have said, for a class `this` is the _reference_ to the current object, i.e. a pointer. If the compiler allowed assigning to it, it would not modify the contents of your object. If you want to assign all of the elements at once, you can use `tupleof` (untested): this.tupleof = other.tupleof; I'm quite certain this wouldn't copy the derived data. So be careful when doing this, you can only do this on final classes. Right, this is dangerous for classes.
Re: How do you make a copy TO and object when you're INSIDE of it?
On 7/24/15 4:47 AM, Marc =?UTF-8?B?U2Now7x0eiI=?= schue...@gmx.net wrote: Apart from what others have said, for a class `this` is the _reference_ to the current object, i.e. a pointer. If the compiler allowed assigning to it, it would not modify the contents of your object. If you want to assign all of the elements at once, you can use `tupleof` (untested): this.tupleof = other.tupleof; I'm quite certain this wouldn't copy the derived data. So be careful when doing this, you can only do this on final classes. -Steve
Re: How do you make a copy TO and object when you're INSIDE of it?
On 7/23/15 9:30 PM, Enjoys Math wrote:
Here's my code:
module grammar;
class Grammar(T : ulong) {
this(const T[] str) {
auto grammar = str in grammarCache;
if (grammar) {
this = grammar.dup;
} else {
this = approximateSmallestGrammar(str);
grammarCache[str] = this.dup;
}
}
static Grammar approximateSmallestGrammar(const T[] str) {
return new Grammar();
}
@property Grammar dup() {
}
private:
this() {}
static Grammar[T[]] grammarCache;
};
Compiler says 'this' is not an lvalue. How would I accomplish what I want?
You're approaching this wrong. Do the lookup before deciding whether to
instantiate a new object:
static Grammar getGrammar(const T[] str) {
if(auto x = str in grammarCache)
return *x;
else
{
auto g = new Grammar;
grammarCache[str] = g;
return g;
}
}
If you always want to dup, then do it outside the lookup. Don't do it in
the constructor, you already have an object by then.
-Steve
Re: How do you make a copy TO and object when you're INSIDE of it?
On Friday, 24 July 2015 at 03:12:43 UTC, Steven Schveighoffer
wrote:
On 7/23/15 9:30 PM, Enjoys Math wrote:
[...]
You're approaching this wrong. Do the lookup before deciding
whether to instantiate a new object:
static Grammar getGrammar(const T[] str) {
if(auto x = str in grammarCache)
return *x;
else
{
auto g = new Grammar;
grammarCache[str] = g;
return g;
}
}
If you always want to dup, then do it outside the lookup. Don't
do it in the constructor, you already have an object by then.
-Steve
Thanks. That sounds like a good approach
Re: How do you make a copy TO and object when you're INSIDE of it?
On Friday, July 24, 2015 01:30:55 Enjoys Math via Digitalmars-d-learn wrote:
Here's my code:
module grammar;
class Grammar(T : ulong) {
this(const T[] str) {
auto grammar = str in grammarCache;
if (grammar) {
this = grammar.dup;
} else {
this = approximateSmallestGrammar(str);
grammarCache[str] = this.dup;
}
}
static Grammar approximateSmallestGrammar(const T[] str) {
return new Grammar();
}
@property Grammar dup() {
}
private:
this() {}
static Grammar[T[]] grammarCache;
};
Compiler says 'this' is not an lvalue. How would I accomplish
what I want?
Assign to the members individually rather than the whole object at once.
- Jonathan M Davis
