Declaring assignments

Syntax

BD>assign  A [Indexlist] = [( )][ ] [ [( )][ ] [ ]]

where A is an alphanumeric representing the name of an assignment, are names of quantities, Indexlist is a list of varying indices, and are equations.

The ASSIGN:  command is used to establish linear relationships. The naming part of the ASSIGN:  command consists of a name A followed optionally by a list of varying indices. The name A might include integer indices, but as it is not possible to mix integer and varying indices in the naming part, this would preclude the option of following the name with a list of varing indices.

Indexlist is a list of varying indices, i.e. a period symbol `.' followed by an alphabetic character. Where there are many indices, a different alphabetic character must be selected for the different indices.

are valid equations which will serve as coefficients for the quantity which it precedes, if any. Each equation may refer to the - as yet unknown - indices given in the naming part. The equations are not evaluated until the assignment is accessed, so these equations may also contain functions and other material whose values are as yet unknown or undefined. It is not necessary for an equation to act as a coefficient, as these unaccompanied equations are treated as scalar parts to the assignment.

Each of is typically one of the following:

• an element or base name
• an assignment name
• a component name

You are not restricted to these choices, but they are the only meaningful types from the point of view of building the assignment: unrecognised quantities are ignored. (This may mean that a spelling mistake passes unnoticed.) As for the equations serving as their coefficients, these names are accessed only when the assignment is actually used, and so they need not exist when the ASSIGN:  command is given, but should exist when the assignment is used.