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digitalmars.D - Q: how to do AA of delegates keyed by int?

reply Brian Chapman <nospam-for-brian see-post-for-address.net> writes:
Help? I'm having trouble figuring out how to get a delegate out of an AA.

	void delegate() hash [int];
	
	int key = 5;
	hash[key] = delegate void() {printf ("whee!\n");};

Now how do I go about getting that value out?

	void delegate() fn = (key in hash);

doesn't work and neither does:

	void delegate()* fn = (key in hash);

which according to the docs I would think is how it is supposed to work 
seeing how it's supposed to return a pointer to the value type. But the 
compiler says:

"cannot implicitly convert expression key in hash of type int to void 
delegate()*"

I give up. What am I doing wrong?

Thanks in advance for putting up with my lameness. ;-)
Feb 01 2005
next sibling parent Carlos Santander <Carlos_member pathlink.com> writes:
In article <ctns13$8fu$1 digitaldaemon.com>, Brian Chapman says...

Help? I'm having trouble figuring out how to get a delegate out of an AA.

	void delegate() hash [int];
	
	int key = 5;
	hash[key] = delegate void() {printf ("whee!\n");};

Now how do I go about getting that value out?

	void delegate() fn = (key in hash);

doesn't work and neither does:

	void delegate()* fn = (key in hash);


This one works for me (dmd 0.111, winxp)


which according to the docs I would think is how it is supposed to work 
seeing how it's supposed to return a pointer to the value type. But the 
compiler says:

"cannot implicitly convert expression key in hash of type int to void 
delegate()*"

I give up. What am I doing wrong?

Thanks in advance for putting up with my lameness. ;-)


----------------
Carlos Santander
Feb 01 2005
prev sibling next sibling parent reply Stewart Gordon <smjg_1998 yahoo.com> writes:
Brian Chapman wrote:

 Help? I'm having trouble figuring out how to get a delegate out of an AA.
 
     void delegate() hash [int];
     
     int key = 5;
     hash[key] = delegate void() {printf ("whee!\n");};
 
 Now how do I go about getting that value out?


Have you tried the 'normal' method?

     void delegate() fn = hash[key];


     void delegate() fn = (key in hash);
 
 doesn't work


Correct, as the InExpression should be of type pointer to delegate.


 and neither does:
 
     void delegate()* fn = (key in hash);
 
 which according to the docs I would think is how it is supposed to work 
 seeing how it's supposed to return a pointer to the value type. But the 
 compiler says:
 
 "cannot implicitly convert expression key in hash of type int to void a
 delegate()*"


<snip>

This should work.  It looks as if the in operator has a bug or two with 
determining its return type.

Stewart.

-- 
My e-mail is valid but not my primary mailbox.  Please keep replies on 
the 'group where everyone may benefit.
Feb 01 2005
parent reply pragma <pragma_member pathlink.com> writes:
In article <cto6bg$kkb$1 digitaldaemon.com>, Stewart Gordon says...

 "cannot implicitly convert expression key in hash of type int to void a
 delegate()*"


<snip>

This should work.  It looks as if the in operator has a bug or two with 
determining its return type.


Actually, its not a bug.  The 'in' operator is a 'boolean' operation ("does this
key exist in the map?"), so it returns 'int' (true/false actually).  

Also, Stewart's suggestion of "hash[key]" is the correct approach, however it
does have the side-effect of generating an empty value for 'key' (the AA grows
as a result) if the key doesn't already exist in the map.  The result is 'fn'
gets assigned null, but future checks to "key in hash" will return true, not
false.

The side-effect free code is like this:

 void delegate fn;
 if(key in hash){
     fn = hash[key];
 }


- EricAnderton at yahoo
Feb 01 2005
next sibling parent reply =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
pragma wrote:


 Actually, its not a bug.  The 'in' operator is a 'boolean' operation ("does
this
 key exist in the map?"), so it returns 'int' (true/false actually).  


The return type of "in" was changed in DMD 0.107, from bit to pointer.

http://www.digitalmars.com/d/changelog.html#new0107

 InExpressions now, instead of returning a bit, return a pointer to the
 associative array element if the key is present, null if it is not. This
 obviates the need for many double lookups.


http://www.digitalmars.com/d/arrays.html#associative

 The InExpression yields a pointer to the value if the key is in the
 associative array, or null if not:
 
 	int* p;
 	p = ("hello" in b);
 	if (p != null)
 		...


Not that D cares about the difference between false and null anyway.	

--anders
Feb 01 2005
parent reply pragma <pragma_member pathlink.com> writes:
In article <cto98f$njs$1 digitaldaemon.com>,
=?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= says...

pragma wrote:


 Actually, its not a bug.  The 'in' operator is a 'boolean' operation ("does
this
 key exist in the map?"), so it returns 'int' (true/false actually).  


The return type of "in" was changed in DMD 0.107, from bit to pointer.

http://www.digitalmars.com/d/changelog.html#new0107

 InExpressions now, instead of returning a bit, return a pointer to the
 associative array element if the key is present, null if it is not. This
 obviates the need for many double lookups.




Well, crap.  Sorry if I mislead anyone. :(

I'll read the changelog a little more closely for now on!

- EricAnderton at yahoo
Feb 01 2005
parent =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
pragma wrote:


The return type of "in" was changed in DMD 0.107, from bit to pointer.





 Well, crap.  Sorry if I mislead anyone. :(
 
 I'll read the changelog a little more closely for now on!


On the contrary, your "no side-effects" code still works -
and seems to be the only one not affected by new "in" bugs ?

"if (key in hash)" still works, just as "if (object)" does.

--anders
Feb 01 2005
prev sibling next sibling parent "Regan Heath" <regan netwin.co.nz> writes:
On Tue, 1 Feb 2005 15:56:43 +0000 (UTC), pragma  
<pragma_member pathlink.com> wrote:

 In article <cto6bg$kkb$1 digitaldaemon.com>, Stewart Gordon says...

 "cannot implicitly convert expression key in hash of type int to void a
 delegate()*"


 <snip>

 This should work.  It looks as if the in operator has a bug or two with
 determining its return type.


 Actually, its not a bug.  The 'in' operator is a 'boolean' operation  
 ("does this key exist in the map?"), so it returns 'int' (true/false  
 actually).


Didn't this change? i.e.

"What's New for D 0.107
Nov 29, 2004
...
InExpressions now, instead of returning a bit, return a pointer to the  
associative array element if the key is present, null if it is not. This  
obviates the need for many double lookups."

http://www.digitalmars.com/d/arrays.html#associative

"The InExpression yields a pointer to the value if the key is in the  
associative array, or null if not:

int* p;
p = ("hello" in b);
if (p != null)
..."

<snip>

Regan
Feb 01 2005
prev sibling parent reply Brian Chapman <nospam-for-brian see-post-for-address.net> writes:
On 2005-02-01 09:56:43 -0600, pragma <pragma_member pathlink.com> said:

 
 The side-effect free code is like this:

 void delegate fn;
 if(key in hash){
 fn = hash[key];
 }


 
 - EricAnderton at yahoo


Thanks Everyone!

Walter's suspicion was correct. I was indeed using an older version 
(but yet reading the latest docs). I'm still using GDC-0.08/GCC-3.3.4 
(on Mac OS X 10.2.8) because I couldn't get GDC-0.10 to work with 
GCC-3.3.4 which means I'm probably going to have to download the latest 
GCC. However, I live on a puny modem (56k that only connects at 28.8) 
and so I procrastinate downloading big files a lot, GCC being one of 
them. But yeah I should get it done nonetheless.

Anyway, I was able to get it to work with Eric's side-effect free code. 
So thank you for that! I guess a little double-lookup won't hurt me 
till I pull in the new GCC/GDC.

Thanks again guys. You big! Me small. ;-)
Feb 01 2005
parent reply =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= <afb algonet.se> writes:
Brian Chapman wrote:


 Walter's suspicion was correct. I was indeed using an older version (but 
 yet reading the latest docs). I'm still using GDC-0.08/GCC-3.3.4 (on Mac 
 OS X 10.2.8) because I couldn't get GDC-0.10 to work with GCC-3.3.4 
 which means I'm probably going to have to download the latest GCC. 


I'm using GDC-0.10 with GCC-3.3.5, but on the latest Mac OS X 10.3.7...

Did you post the compiler errors you get on the digitalmars.D.gnu group?


 However, I live on a puny modem (56k that only connects at 28.8) and so 
 I procrastinate downloading big files a lot, GCC being one of them. But 
 yeah I should get it done nonetheless.


Can't you just order a CD ? Lots of places sell distfiles like gcc.

Still have to get Mango 1.1 to compile with this compiler/platform, 
though. And of course, there's also the goodies from DMD 0.111/0.112

--anders
Feb 02 2005
parent Brian Chapman <nospam-for-brian see-post-for-address.net> writes:
On 2005-02-02 04:09:14 -0600, =?ISO-8859-1?Q?Anders_F_Bj=F6rklund?= 
<afb algonet.se> said:


 Brian Chapman wrote:
 

 Walter's suspicion was correct. I was indeed using an older version 
 (but yet reading the latest docs). I'm still using GDC-0.08/GCC-3.3.4 
 (on Mac OS X 10.2.8) because I couldn't get GDC-0.10 to work with 
 GCC-3.3.4 which means I'm probably going to have to download the latest 
 GCC.


 
 I'm using GDC-0.10 with GCC-3.3.5, but on the latest Mac OS X 10.3.7...
 
 Did you post the compiler errors you get on the digitalmars.D.gnu group?


Well, you wont believe this but I went back to nail down the problem so 
I could tell you what it was and found out it was something really 
simple, all be it, very odd. Somehow a -Werror flag had creeped into my 
DFLAGS makefile variable. It was causing GDC to output a sparse object 
file and leaving a nice .s file in the working directory for each .d 
file compiled. Took that W flag out and it works fine. Put it back in 
and weirdness. You know, those GCC guys are never gonna take us 
seriously with that kind of goofiness going on. ;-)



 However, I live on a puny modem (56k that only connects at 28.8) and so 
 I procrastinate downloading big files a lot, GCC being one of them. But 
 yeah I should get it done nonetheless.


 
 Can't you just order a CD ? Lots of places sell distfiles like gcc.


Yeah I used to do that. Place called Cheap Bytes. I don't know if they 
are still around. It's not so bad if I remember to stick wget on it 
before I go to bed. ;-)



 Still have to get Mango 1.1 to compile with this compiler/platform, 
 though. And of course, there's also the goodies from DMD 0.111/0.112
 
 --anders
Feb 03 2005
prev sibling parent "Walter" <newshound digitalmars.com> writes:
"Brian Chapman" <nospam-for-brian see-post-for-address.net> wrote in message
news:ctns13$8fu$1 digitaldaemon.com...

 I give up. What am I doing wrong?


I think you might be using an older DMD version. Try upgrading to 0.111.
Feb 01 2005