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/GNU Fortran 7

9.206 NORM2 — Euclidean vector norms

Description:

Calculates the Euclidean vector norm (L_2 norm) of of ARRAY along dimension DIM.

Standard:

Fortran 2008 and later

Class:

Transformational function

Syntax:
RESULT = NORM2(ARRAY[, DIM])
Arguments:
ARRAY Shall be an array of type REAL
DIM (Optional) shall be a scalar of type INTEGER with a value in the range from 1 to n, where n equals the rank of ARRAY.
Return value:

The result is of the same type as ARRAY.

If DIM is absent, a scalar with the square root of the sum of all elements in ARRAY squared is returned. Otherwise, an array of rank n-1, where n equals the rank of ARRAY, and a shape similar to that of ARRAY with dimension DIM dropped is returned.

Example:
PROGRAM test_sum
  REAL :: x(5) = [ real :: 1, 2, 3, 4, 5 ]
  print *, NORM2(x)  ! = sqrt(55.) ~ 7.416
END PROGRAM

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https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gfortran/NORM2.html