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# Technical Reference: Base Operating System and Extensions, Volume 1

## hypot, hypotf, or hypotl Subroutine

### Purpose

Computes the Euclidean distance function and complex absolute value.

### Libraries

IEEE Math Library (libm.a)
System V Math Library (libmsaa.a)

### Syntax

`#include <math.h>`

double hypot ( x, y)
double x, y;

```float hypotf (x, y)
float x;
float y;

long double hypotl (x, y)
long double x;
long double y;```

### Description

The hypot, hypotf and hypotl subroutines compute the value of the square root of x2 + y2 without undue overflow or underflow.

An application wishing to check for error situations should set the errno global variable to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these subroutines. Upon return, if errno is nonzero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is nonzero, an error has occurred.

### Parameters

 x Specifies some double-precision floating-point value. y Specifies some double-precision floating-point value.

### Return Values

Upon successful completion, the hypot, hypotf and hypotl subroutines return the length of the hypotenuse of a right-angled triangle with sides of length x and y.

If the correct value would cause overflow, a range error occurs and the hypotf and hypotl subroutines return the value of the macro HUGE_VALF and HUGE_VALL, respectively.

If x or y is ±Inf, +Inf is returned (even if one of x or y is NaN).

If x or y is NaN, and the other is not ±Inf, a NaN is returned.

If both arguments are subnormal and the correct result is subnormal, a range error may occur and the correct result is returned.

### Error Codes

When using the libm.a (-lm) library, if the correct value overflows, the hypot subroutine returns a HUGE_VAL value.

Note
(hypot (INF, value) and hypot (value, INF) are both equal to +INF for all values, even if value = NaN.

When using libmsaa.a (-lmsaa), if the correct value overflows, the hypot subroutine returns HUGE_VAL and sets the global variable errno to ERANGE.

These error-handling procedures may be changed with the matherr subroutine when using the libmsaa.a (-lmsaa) library.

### Related Information

The matherr (matherr Subroutine) subroutine, sqrt subroutine.

Subroutines Overview in AIX 5L Version 5.2 General Programming Concepts: Writing and Debugging Programs.

math.h in AIX 5L Version 5.2 Files Reference.

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