Indirection Operator (@)

Indirection is a technique that provides dynamic runtime substitution of part or all of a command line, a command, or a command argument by the contents of a data field.

Indirection is specified by the indirection operator (@) and, except for subscript indirection, takes the form:

@variable

where variable identifies the variable from which the substitution value is to be taken. All variables referenced in the substitution value are public variables, even when used in a procedure. The variable can be an array node.

The following routine illustrates that indirection looks at the entire variable value to its right.

IndirectionExample
 SET x = "ProcA"
 SET x(3) = "ProcB"
 ; The next line will do ProcB, NOT ProcA(3)
 DO @x(3)
 QUIT
ProcA(var)
 WRITE !,"At ProcA"
 QUIT
ProcB(var)
 WRITE !,"At ProcB"
 QUIT

For details, see the Indirection (@) reference page.

Note:

Although indirection can promote more economical and more generalized coding than would be otherwise available, it is never essential. You can always duplicate the effect of indirection by other means, such as by using the XECUTE command.

Pattern Match Operator (?)