Difference between revisions of "Template:cpp/container/front"
From cppreference.com
(mention UB first) |
m |
||
| Line 6: | Line 6: | ||
}} | }} | ||
{{ddcl list item | notes={{cpp/container/mark since c++11 | {{{1|}}} }} | | {{ddcl list item | notes={{cpp/container/mark since c++11 | {{{1|}}} }} | | ||
| − | const_reference front() const; | + | constexpr const_reference front() const; |
}} | }} | ||
{{ddcl list end}} | {{ddcl list end}} | ||
| Line 25: | Line 25: | ||
===Notes=== | ===Notes=== | ||
For a container {{tt|c}}, the expression {{c|c.front()}} is equivalent to {{c|*c.begin()}}. | For a container {{tt|c}}, the expression {{c|c.front()}} is equivalent to {{c|*c.begin()}}. | ||
| + | |||
| + | Const version is marked as constexpr since c++14. | ||
===Example=== | ===Example=== | ||
Revision as of 10:02, 21 May 2013
Template:ddcl list begin <tr class="t-dcl ">
<td class="t-dcl-nopad">reference front();
</td>
<td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">
<td class="t-dcl-nopad">constexpr const_reference front() const;
</td>
<td class="t-dcl-nopad"> </td> <td class="t-dcl-nopad"> </td> </tr> Template:ddcl list end
Returns a reference to the first element in the container.
Calling front on an empty container is undefined.
Contents |
Parameters
(none)
Return value
reference to the first element
Complexity
Constant
Notes
For a container c, the expression c.front() is equivalent to *c.begin().
Const version is marked as constexpr since c++14.
Example
The following code uses front to display the first element of a std::{{{1}}}<char>:
Run this code
#include <{{{1}}}> #include <iostream> int main() { std::{{{1}}}<char> letters {'o', 'm', 'g', 'w', 't', 'f'}; if (!letters.empty()) { std::cout << "The first character is: " << letters.front() << '\n'; } }
Output:
The first character is o
