digitalmars.D.bugs - Weird hash (associative array) init behaviour?
- Helmut Leitner (37/37) May 12 2004 The following small program
- Ivan Senji (5/42) May 12 2004 Shouldn't you pass Bag as inout Bag if you are trying to
- Helmut Leitner (7/31) May 12 2004 Maybe I should use inout (I thought of it as an object pointer,
- Ben Hinkle (12/43) May 12 2004 The statement
- C (6/53) May 12 2004 Yes, use 'in' to determine if a key exists, and isnt 'inout' the default...
- Andrew Edwards (2/66) May 12 2004
- C (7/72) May 12 2004 Huh thats weird, i could of swore at one time it was inout, maybe it
-
Carlos Santander B.
(20/20)
May 12 2004
"C"
- Ben Hinkle (10/31) May 12 2004 For all types it is "in". To see why classes aren't "inout" try
- J Anderson (20/41) May 13 2004 To be more specific. Everything is passed as *in* by default. Its just...
The following small program
alias char[] Str;
alias int [char []] Bag;
Bag bag1;
Bag bag2;
void BagAddElem(Bag bag,Str key)
{
int count=bag[key];
if(count>0) {
bag[key]=count+1;
} else {
bag[key.dup]=1;
}
}
int main()
{
int count=bag2["TEST"];
BagAddElem(bag1,"TEST");
BagAddElem(bag2,"TEST");
printf("bag1.keys.length=%d\n",bag1.keys.length);
printf("bag2.keys.length=%d\n",bag2.keys.length);
return 0;
}
creates the output:
bag1.keys.length=0
bag2.keys.length=1
Expected is:
bag1.keys.length=1
bag2.keys.length=1
The only difference is the first access to the two bags.
(1) bag1 is first questioned (while still empty)
(2) bag2 gets an element added frist
(1) seems to disable bag1 for all further accesses (this hit me
in a real world program, where 193.000 adds didn't get into the bag).
--
Helmut Leitner leitner hls.via.at
Graz, Austria www.hls-software.com
May 12 2004
"Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...The following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.int main() { int count=bag2["TEST"]; BagAddElem(bag1,"TEST"); BagAddElem(bag2,"TEST"); printf("bag1.keys.length=%d\n",bag1.keys.length); printf("bag2.keys.length=%d\n",bag2.keys.length); return 0; } creates the output: bag1.keys.length=0 bag2.keys.length=1 Expected is: bag1.keys.length=1 bag2.keys.length=1 The only difference is the first access to the two bags. (1) bag1 is first questioned (while still empty) (2) bag2 gets an element added frist (1) seems to disable bag1 for all further accesses (this hit me in a real world program, where 193.000 adds didn't get into the bag). -- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
May 12 2004
Ivan Senji wrote:"Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...Maybe I should use inout (I thought of it as an object pointer, not as an array reference), but bag2 *does* change through the same interface. The only difference is the initial query of bag2. -- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.comThe following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.
May 12 2004
"Helmut Leitner" <helmut.leitner wikiservice.at> wrote in message news:40A266E1.76885A65 wikiservice.at...Ivan Senji wrote:The statement int count=bag2["TEST"]; will add TEST to bag2 with initialized value (which is 0 for int) if it isn't already in there. An associative array has the same length field and data pointer fields as a dynamic array. So when you pass it to a function if the function either 1) calls rehash, which would reallocate the data pointer or 2) adds the first element to an unused array (the case you have here) then you should make the variable "inout" so that those changes are reflected in the original array - assuming that is what you want."Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...Maybe I should use inout (I thought of it as an object pointer, not as an array reference), but bag2 *does* change through the same interface. The only difference is the initial query of bag2.The following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.-- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
May 12 2004
Yes, use 'in' to determine if a key exists, and isnt 'inout' the default anyway ? On Wed, 12 May 2004 14:35:01 -0400, Ben Hinkle <bhinkle mathworks.com> wrote:"Helmut Leitner" <helmut.leitner wikiservice.at> wrote in message news:40A266E1.76885A65 wikiservice.at...-- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/Ivan Senji wrote:The statement int count=bag2["TEST"]; will add TEST to bag2 with initialized value (which is 0 for int) if it isn't already in there. An associative array has the same length field and data pointer fields as a dynamic array. So when you pass it to a function if the function either 1) calls rehash, which would reallocate the data pointer or 2) adds the first element to an unused array (the case you have here) then you should make the variable "inout" so that those changes are reflected in the original array - assuming that is what you want."Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...Maybe I should use inout (I thought of it as an object pointer, not as an array reference), but bag2 *does* change through the same interface. The only difference is the initial query of bag2.The following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.-- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
May 12 2004
C wrote:Yes, use 'in' to determine if a key exists, and isnt 'inout' the default anyway ?No the default is 'in'!On Wed, 12 May 2004 14:35:01 -0400, Ben Hinkle <bhinkle mathworks.com> wrote:"Helmut Leitner" <helmut.leitner wikiservice.at> wrote in message news:40A266E1.76885A65 wikiservice.at...Ivan Senji wrote:The statement int count=bag2["TEST"]; will add TEST to bag2 with initialized value (which is 0 for int) if it isn't already in there. An associative array has the same length field and data pointer fields as a dynamic array. So when you pass it to a function if the function either 1) calls rehash, which would reallocate the data pointer or 2) adds the first element to an unused array (the case you have here) then you should make the variable "inout" so that those changes are reflected in the original array - assuming that is what you want."Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...Maybe I should use inout (I thought of it as an object pointer, not as an array reference), but bag2 *does* change through the same interface. The only difference is the initial query of bag2.The following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.-- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
May 12 2004
Huh thats weird, i could of swore at one time it was inout, maybe it changed. Thanks On Wed, 12 May 2004 17:24:36 -0400, Andrew Edwards <edwardsac spamfreeusa.org> wrote:C wrote:-- Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/Yes, use 'in' to determine if a key exists, and isnt 'inout' the default anyway ?No the default is 'in'!On Wed, 12 May 2004 14:35:01 -0400, Ben Hinkle <bhinkle mathworks.com> wrote:"Helmut Leitner" <helmut.leitner wikiservice.at> wrote in message news:40A266E1.76885A65 wikiservice.at...Ivan Senji wrote:The statement int count=bag2["TEST"]; will add TEST to bag2 with initialized value (which is 0 for int) if it isn't already in there. An associative array has the same length field and data pointer fields as a dynamic array. So when you pass it to a function if the function either 1) calls rehash, which would reallocate the data pointer or 2) adds the first element to an unused array (the case you have here) then you should make the variable "inout" so that those changes are reflected in the original array - assuming that is what you want."Helmut Leitner" <leitner hls.via.at> wrote in message news:40A23CCD.F78AD327 hls.via.at...Maybe I should use inout (I thought of it as an object pointer, not as an array reference), but bag2 *does* change through the same interface. The only difference is the initial query of bag2.The following small program alias char[] Str; alias int [char []] Bag; Bag bag1; Bag bag2; void BagAddElem(Bag bag,Str key) { int count=bag[key]; if(count>0) { bag[key]=count+1; } else { bag[key.dup]=1; } }Shouldn't you pass Bag as inout Bag if you are trying to change it inside the function? That is the reason that bag1 and bag2 size doesn't change.-- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
May 12 2004
"C" <qbert atari-soldiers.com> wrote in message news:opr7w18bltaoygh6 news.digitalmars.com | Huh thats weird, i could of swore at one time it was inout, maybe it | changed. | | Thanks | | On Wed, 12 May 2004 17:24:36 -0400, Andrew Edwards | <edwardsac spamfreeusa.org> wrote: | || C wrote: ||| Yes, use 'in' to determine if a key exists, and isnt 'inout' the ||| default anyway ? || || No the default is 'in'! || For classes it is "inout". For arrays, I don't remember. For the rest, it's "in". ----------------------- Carlos Santander Bernal
May 12 2004
Ben Hinkle <bhinkle4 juno.com> Carlos Santander B. wrote:"C" <qbert atari-soldiers.com> wrote in message news:opr7w18bltaoygh6 news.digitalmars.com | Huh thats weird, i could of swore at one time it was inout, maybe it | changed. | | Thanks | | On Wed, 12 May 2004 17:24:36 -0400, Andrew Edwards | <edwardsac spamfreeusa.org> wrote: | || C wrote: ||| Yes, use 'in' to determine if a key exists, and isnt 'inout' the ||| default anyway ? || || No the default is 'in'! || For classes it is "inout". For arrays, I don't remember. For the rest, it's "in".For all types it is "in". To see why classes aren't "inout" try void foo(Object obj){obj=null;} // change obj in caller? it shouldn't int main() { Object x = new Object(); foo(x); printf("%p\n",x); return 0; } Object references are passed by value.----------------------- Carlos Santander Bernal
May 12 2004
Carlos Santander B. wrote:"C" <qbert atari-soldiers.com> wrote in message news:opr7w18bltaoygh6 news.digitalmars.com | Huh thats weird, i could of swore at one time it was inout, maybe it | changed. | | Thanks | | On Wed, 12 May 2004 17:24:36 -0400, Andrew Edwards | <edwardsac spamfreeusa.org> wrote: | || C wrote: ||| Yes, use 'in' to determine if a key exists, and isnt 'inout' the ||| default anyway ? || || No the default is 'in'! || For classes it is "inout". For arrays, I don't remember. For the rest, it's "in". ----------------------- Carlos Santander BernalTo be more specific. Everything is passed as *in* by default. Its just that arrays and classes are references that allows you be able to modify the data and pass it back. For instance, what does this do? class A { void func() { } } void func(A a) { a = new A; } int main( char[][] args ) { A a; func(a); a.func(); return 0; } -- -Anderson: http://badmama.com.au/~anderson/
May 13 2004