---
name: "__gnu_cxx::select1st"
section: "3cxx"
platform: "linux"
package: "libstdc++-12-doc"
version: "12.4.0-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/__gnu_cxx::select1st/3cxx"
---

# \_\_gnu\_cxx::select1st(3cxx)

An SGI extension .

## NAME

\_\_gnu\_cxx::select1st\< \_Pair \> - An **SGI extension** .

## SYNOPSIS

`#include <functional>`

Inherits std::\_Select1st\< \_Pair \>.

### Public Types

typedef \_Pair **argument\_type**\
 `argument_type` is the type of the argument  typedef \_Pair::first\_type **result\_type**\
 `result_type` is the return type

### Public Member Functions

\_Pair::first\_type & **operator()** (\_Pair &\_\_x) const\
 template\<typename \_Pair2 \> \_Pair2::first\_type & **operator()** (\_Pair2 &\_\_x) const\
 const \_Pair::first\_type & **operator()** (const \_Pair &\_\_x) const\
 template\<typename \_Pair2 \> const \_Pair2::first\_type & **operator()** (const \_Pair2 &\_\_x) const\

## Detailed Description

### template\<class \_Pair\>

struct \_\_gnu\_cxx::select1st\< \_Pair \>"An **SGI extension** .

## Member Typedef Documentation

### typedef \_Pair std::unary\_function\< \_Pair , \_Pair::first\_type \>::argument\_type` [inherited]`

`argument_type` is the type of the argument

### typedef \_Pair::first\_type std::unary\_function\< \_Pair , \_Pair::first\_type \>::result\_type` [inherited]`

`result_type` is the return type

## Author

Generated automatically by Doxygen for libstdc++ from the source code.