---
name: "zslect.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/zslect.f"
---

# zslect.f(3)

## NAME

TESTING/EIG/zslect.f

## SYNOPSIS

### Functions/Subroutines

logical function **zslect** (z)\
 **ZSLECT**

## Function/Subroutine Documentation

### logical function zslect (complex\*16 z)

**ZSLECT**

**Purpose:**

```
!>
!> ZSLECT returns .TRUE. if the eigenvalue Z is to be selected,
!> otherwise it returns .FALSE.
!> It is used by ZCHK41 to test if ZGEES successfully sorts eigenvalues,
!> and by ZCHK43 to test if ZGEESX successfully sorts eigenvalues.
!>
!> The common block /SSLCT/ controls how eigenvalues are selected.
!> If SELOPT = 0, then ZSLECT return .TRUE. when real(Z) is less than
!> zero, and .FALSE. otherwise.
!> If SELOPT is at least 1, ZSLECT returns SELVAL(SELOPT) and adds 1
!> to SELOPT, cycling back to 1 at SELMAX.
!>
```

**Parameters**

*Z*

```
!>          Z is COMPLEX*16
!>          The eigenvalue Z.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **55** of file **zslect.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.