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Difference between revisions of "Template:cpp/container/shrink to fit"

From cppreference.com
m (Fixed typo: "constructd" in example code & results as it affected cpp/container/vector/shrink_to_fit)
m (→‎Synopsis: +(constexpr since C++20) to *)
 
(20 intermediate revisions by 11 users not shown)
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{{cpp/container/{{{1|}}}/title | shrink_to_fit}}
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{{cpp/container/{{{1|}}}/title|shrink_to_fit}}
 
{{cpp/container/{{{1|}}}/navbar}}
 
{{cpp/container/{{{1|}}}/navbar}}
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{{ddcl | notes={{mark since c++11}} |
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{{dcl begin}}
 +
{{#ifeq:{{{1}}}|vector|
 +
{{dcl|notes={{mark constexpr since c++20}}|
 
void shrink_to_fit();
 
void shrink_to_fit();
 
}}
 
}}
 +
|
 +
{{dcl|
 +
void shrink_to_fit();
 +
}}
 +
}}
 +
{{dcl end}}
 +
 
Requests the removal of unused capacity.
 
Requests the removal of unused capacity.
  
−
It is a non-binding request to reduce {{#ifeq:{{{1|}}}|vector|{{rlpt|capacity}}|{{tt|capacity}}}} to {{rlpt|size}}. It depends on the implementation if the request is fulfilled.  
+
It is a non-binding request to {{#ifeq:{{{1|}}}|vector|reduce {{lc|capacity()}} to {{lc|size()}}|reduce the memory usage without changing the size of the sequence}}. It depends on the implementation whether the request is fulfilled.  
 +
 
 +
{{cpp/container/note iterator invalidation|{{{1|}}}|shrink_to_fit}}
  
 
===Parameters===
 
===Parameters===
 
(none)
 
(none)
 +
 +
{{par begin}}
 +
{{par hreq}}
 +
{{par req insertable|T|MoveInsertable|notes={{mark since c++11}}}}
 +
{{par end}}
  
 
===Return value===
 
===Return value===
Line 15: Line 31:
  
 
===Complexity===
 
===Complexity===
−
Constant
+
At most linear in the size of the container.
  
−
{{#ifeq: {{{1|}}}|vector|===Example===
+
{{rrev|since=c++11|
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{{example
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===Exceptions===
−
|
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If an exception is thrown other than by the move constructor of a non-{{named req|CopyInsertable}} {{tt|T}}, there are no effects.
−
| code=
+
}}
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#include <iostream>
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−
#include <{{{1}}}>
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int main()
+
−
{
+
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    std::{{{1}}}<int> v;
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−
    std::cout << "Default-constructed capacity is " << v.capacity() << '\n';
+
−
    v.resize(100);
+
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    std::cout << "Capacity of a 100-element {{{1}}} is " << v.capacity() << '\n';
+
−
    v.clear();
+
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    std::cout << "Capacity after clear() is " << v.capacity() << '\n';
+
−
    v.shrink_to_fit();
+
−
    std::cout << "Capacity after shrink_to_fit() is " << v.capacity() << '\n';
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−
}
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−
| output=
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Default-constructed capacity is 0
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Capacity of a 100-element {{{1}}} is 100
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−
Capacity after clear() is 100
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−
Capacity after shrink_to_fit() is 0
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−
}}}}
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−
===See also===
+
  
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{{dcl list begin}}
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===Notes===
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{{dcl list template | cpp/container/dcl list size |{{{1|}}}}}
+
In libstdc++, {{tt|shrink_to_fit()}} is [https://gcc.gnu.org/onlinedocs/libstdc++/manual/strings.html#strings.string.shrink not available] in C++98 mode.
−
{{#ifeq: {{{1|}}}|vector|{{dcl list template | cpp/container/dcl list capacity |{{{1|}}}}}}}
+
 
−
{{dcl list end}}
+
===Example===
 +
{{include|cpp/container/{{{1|}}}/example_shrink_to_fit}}
 +
 
 +
===Defect reports===
 +
{{dr list begin}}
 +
{{dr list item|wg=lwg|dr={{#ifeq:{{{1|}}}|vector|755|850}}|std=C++98|before={{tt|std::{{{1|}}}}} lacked explicit shrink-to-fit operations|after=provided}}
 +
{{dr list item|wg=lwg|dr=2033|std=C++11|before=1. {{tt|T}} was not required to be {{named req|MoveInsertable}}<br>2. the complexity requirement was missing|after=1. required<br>2. added}}
 +
{{dr list end}}
 +
 
 +
===See also===
 +
{{dsc begin}}
 +
{{dsc inc|cpp/container/dsc size|{{{1|}}}}}
 +
{{#ifeq:{{{1|}}}|vector|{{dsc inc|cpp/container/dsc capacity|{{{1|}}}}}}}
 +
{{dsc end}}

Latest revision as of 15:15, 5 May 2024

 
C++
 
Containers library
 
void shrink_to_fit();

Requests the removal of unused capacity.

It is a non-binding request to reduce the memory usage without changing the size of the sequence. It depends on the implementation whether the request is fulfilled.

Information on iterator invalidation is copied from here

Contents

[edit] Parameters

(none)

Type requirements
-
T must meet the requirements of MoveInsertable into *this. (since C++11)

[edit] Return value

(none)

[edit] Complexity

At most linear in the size of the container.

Exceptions

If an exception is thrown other than by the move constructor of a non-CopyInsertable T, there are no effects.

(since C++11)

[edit] Notes

In libstdc++, shrink_to_fit() is not available in C++98 mode.

[edit] Example

Templated content.
The link is cpp/container/<PP>/example_shrink_to_fit

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 850 C++98 std:: lacked explicit shrink-to-fit operations provided
LWG 2033 C++11 1. T was not required to be MoveInsertable
2. the complexity requirement was missing 		1. required
2. added

[edit] See also

 returns the number of elements
(public member function of std::{{{1}}}) [edit]
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