FORTRAN Reference Manual

Statements

FORTRAN Reference Manual—528615-001

7-37

Equivalence With Length Differences

You can equivalence fields of different lengths as long as the EQUIVALENCE

statement does not violate the implicit alignment rules of these fields. The following

example equivalences the integer array N and the real array W and shows the

alignment of the two arrays:

DIMENSION n(9), w(6)

EQUIVALENCE (n(1), w(1))

Two elements of the array N occupy the same storage location as one element of the

array W.

Equivalencing Items in Common Blocks

Two entities in a common block cannot be equivalenced to each other, but a variable,

array, or array element in either a calling program or a subprogram can be made

equivalent to an item in a common block. In this case, an EQUIVALENCE statement

must not attempt to expand a common block by adding entities to storage ahead of the

first entity in the block. You can extend a common block beyond its current last storage

location. The following examples illustrate this restriction:

You cannot equivalence elements of two different common blocks.

Example

In the following example, the first five elements of the array RATE share the same

storage locations with the five-element array TOTAL:

DIMENSION rate(30), total(5)

EQUIVALENCE (rate(1), total(1))

Illegal Legal

COMMON xitem COMMON xitem

REAL price(5) REAL price(5)

EQUIVALENCE(xitem,price(5)) EQUIVALENCE(xitem,price(1))

DIMENSION n(9), w(6)

EQUIVALENCE (n(1), w(1))

n(1) n(7)n(4)n(3)n(2) n(8) n(9)n(6)n(5)

W(1) W(2) W(3) W(4) W(5) W(6)

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