Calculates the Euclidean vector norm (L_2 norm) of of ARRAY along dimension DIM.
Fortran 2008 and later
Transformational function
RESULT = NORM2(ARRAY[, DIM]) 
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. 
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 n1, where n equals the rank of ARRAY, and a shape similar to that of ARRAY with dimension DIM dropped is returned.
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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Licensed under the GNU Free Documentation License, Version 1.3.
https://gcc.gnu.org/onlinedocs/gcc7.1.0/gfortran/NORM2.html