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An
array constructor allows a rank-one array to be constructed from
a list of scalar values, arrays of any rank, and implied DO
specifications. The type of an array constructor is taken from the
values in the list which must all have the same type and type parameters
(including character length), and its shape is taken from the number
of values specified. An array constructor may appear in any context in which a
rank-one array expression is allowed. An array with a rank greater
than one may be constructed by passing the array constructor to
the RESHAPE intrinsic
function. If
the list contains only constant values, the array constructor may
be used to initialize a named constant, or it may be used in an
initialization expression in a type declaration statement; however
an array constructor may not be used to initialize variables in
a DATA statement
as this statement may only contain scalar constants. Syntax | |
The syntax of an array constructor is: (/ array-constructor-value-list /) |
- array-constructor-value-list
is a comma-separated list of array-constructor-value - array-constructor-value
is one of: array-constructor-implied-do
- array-constructor-implied-do
is ( array-constructor-value-list, scalar-int-var-name = & |
scalar-int-expression, scalar-int-expression & |
[, scalar-int-expression] ) |
If an array expression appears in a value list, it is treated
as a succession of values appearing in array element order (see
“Array element storage
order”). The extent of an array constructor is the number of values
supplied. If no values were supplied then the array constructor
is zero-sized. For example, the size of the following array constructor: depends on the value of the variable n;
if the value of the variable is less than 10 then the constructor
will contain no values. HP Fortran 90 allows the use of [
and ] in place
of (/ and /).
This notation is an extension to the Fortran 90 Standard. The following are examples of array constructors: ! Array x is assigned three real values. |
j = (/4, 10, k(1:5), 2 + l, & |
(m(n), n = -7,-2),16, 1/) |
! One vector, consisting of 16 integer values, |
PARAMETER (t=(/ 36.0, 37.0/)) |
! The named constant t is a rank-one array |
! initialized with the values 36.0 and 37.0. |
z=RESHAPE((/1,2,3,4,5,6,7,8/), (/2,4/) ) |
! the array constructor is reshaped as 1 3 5 7 |
! and is then assigned to z |
alaska = site("NOME",(/-63,4/)) |
! An array constructor is used for the second |
! component of the structure constructor. |
diagonal = (/ (b(i,i), i=1,n) /) |
hilbert = RESHAPE( (/ ((1.0/(i+j), i=1,n), & |
ident = RESHAPE ( (/ (1, (0, i=1,n), j=1,n-1), & |
As illustrated by the last three examples, an array constructor
with implied DOs
and the RESHAPE
function can be used to construct arrays that cannot be expressed
conveniently with alternative notations. |
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