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digitalmars.D.learn - How to remove the key from the `redBlackTree` with comparator" a <= b

reply "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
I understand that `removeKey` works only with the comparator "a < 
b":
http://dlang.org/phobos/std_container_rbtree.html#.RedBlackTree.removeKey
Removes elements from the container that are equal to the given 
values according to the less comparator.
How do I remove the key from the `redBlackTree` with comparator "a <= b" ? auto rbt = redBlackTree!("a <= b", int)(1, 2, 3, 4, 5, 6, 7); rbt.removeKey(6); foreach (key; rbt) write(key); // prints 1234567
Jun 07 2015
parent reply "anonymous" <anonymous example.com> writes:
On Sunday, 7 June 2015 at 18:42:58 UTC, Dennis Ritchie wrote:
 How do I remove the key from the `redBlackTree` with comparator 
 "a <= b" ?
Do not use '<=' as a comparison function with RedBlackTree. It doesn't meet the requirements. Quoting the documentation [1]:
 Note that less should produce a strict ordering. That is, for 
 two unequal elements a and b, less(a, b) == !less(b, a). 
 less(a, a) should always equal false.
This doesn't hold for '<='.
Jun 07 2015
next sibling parent reply "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
On Sunday, 7 June 2015 at 18:50:47 UTC, anonymous wrote:
 On Sunday, 7 June 2015 at 18:42:58 UTC, Dennis Ritchie wrote:
 How do I remove the key from the `redBlackTree` with 
 comparator "a <= b" ?
Do not use '<=' as a comparison function with RedBlackTree. It doesn't meet the requirements. Quoting the documentation [1]:
 Note that less should produce a strict ordering. That is, for 
 two unequal elements a and b, less(a, b) == !less(b, a). 
 less(a, a) should always equal false.
This doesn't hold for '<='.
OK. But I want to return a `upperBound` segment with the included `key`. It does not suit me: auto rbt = redBlackTree!("a < b", int)(1, 2, 3, 4, 5); writeln(rbt.upperBound(3)); // prints [4, 5] I want it to be so: auto rbt = redBlackTree!("a <= b", int)(1, 2, 3, 4, 5); writeln(rbt.upperBound(3)); // prints [3, 4, 5] How do I do with the comparator "a < b" ?
Jun 07 2015
parent reply "anonymous" <anonymous example.com> writes:
On Sunday, 7 June 2015 at 19:04:08 UTC, Dennis Ritchie wrote:
 OK. But I want to return a `upperBound` segment with the 
 included `key`. It does not suit me:

 auto rbt = redBlackTree!("a < b", int)(1, 2, 3, 4, 5);
 writeln(rbt.upperBound(3)); // prints [4, 5]

 I want it to be so:

 auto rbt = redBlackTree!("a <= b", int)(1, 2, 3, 4, 5);
 writeln(rbt.upperBound(3)); // prints [3, 4, 5]

 How do I do with the comparator "a < b" ?
Use equalRange to get the elements that equal 3, too: writeln(std.range.chain(rbt.equalRange(3), rbt.upperBound(3)));
Jun 07 2015
parent "Dennis Ritchie" <dennis.ritchie mail.ru> writes:
On Sunday, 7 June 2015 at 19:11:25 UTC, anonymous wrote:
 On Sunday, 7 June 2015 at 19:04:08 UTC, Dennis Ritchie wrote:
 auto rbt = redBlackTree!("a <= b", int)(1, 2, 3, 4, 5);
 writeln(rbt.upperBound(3)); // prints [3, 4, 5]

 How do I do with the comparator "a < b" ?
Use equalRange to get the elements that equal 3, too: writeln(std.range.chain(rbt.equalRange(3), rbt.upperBound(3)));
Thank you!
Jun 07 2015
prev sibling parent reply "Per =?UTF-8?B?Tm9yZGzDtnci?= <per.nordlow gmail.com> writes:
On Sunday, 7 June 2015 at 18:50:47 UTC, anonymous wrote:
 Do not use '<=' as a comparison function with RedBlackTree. It 
 doesn't meet the requirements.

 Quoting the documentation [1]:
 Note that less should produce a strict ordering. That is, for 
 two unequal elements a and b, less(a, b) == !less(b, a). 
 less(a, a) should always equal false.
This doesn't hold for '<='.
Could we add a static check for this?
Jun 08 2015
parent Steven Schveighoffer <schveiguy yahoo.com> writes:
On 6/8/15 6:53 AM, "Per =?UTF-8?B?Tm9yZGzDtnci?= 
<per.nordlow gmail.com>" wrote:
 On Sunday, 7 June 2015 at 18:50:47 UTC, anonymous wrote:
 Do not use '<=' as a comparison function with RedBlackTree. It doesn't
 meet the requirements.

 Quoting the documentation [1]:
 Note that less should produce a strict ordering. That is, for two
 unequal elements a and b, less(a, b) == !less(b, a). less(a, a)
 should always equal false.
This doesn't hold for '<='.
Could we add a static check for this?
How would a static check generate a and b generically? -Steve
Jun 08 2015