Using Caché ObjectScript - InterSystems Documentation

Procedures in Detail
If there are more variables in the formal list than there are parameters in the actual list, and a default value is not provided
for each, the extra variables are left undefined. Your function code should include appropriate If tests to make sure that
each function reference provides usable values.
When passing parameters to a user-defined function, you can use passing by value or passing by reference. You can mix
passing by value and passing by reference within the same function call. See Parameter Passing.
Parameter passing can be done by reference or by value.
• System-supplied functions — these can be passed parameters by value only.
• User-defined functions — these can be passed parameters by value or by reference.
• Subroutines can be passed parameters by value or by reference.
• Procedures can be passed parameters by value or by reference.
8.2.5.1 Passing By Value
To pass by value, specify an actual value, an expression, or an unsubscripted local variable name in the actual parameter
list. In the case of an expression, Caché first evaluates the expression and then passes the resulting value. In the case of a
variable name, Caché passes the variable’s current value. Note that a specified variable name must already exist and must
have a value.
Caché implicitly creates and declares any non-public variables used within a procedure, so that already-existing variables
with the same name in calling code are not overwritten. It places the existing values for these variables (if any) on the
program stack. When it invokes the Quit command, Caché executes an implicit Kill command for each of the formal
variables and restores their previous values from the stack.
In the following example, the Set commands use three different forms to pass the same value to the referenced Cube procedure.
Do Start()
Start() PUBLIC {
Set var1=6
Set a=$$Cube(6)
Set b=$$Cube(2*3)
Set c=$$Cube(var1)
Write !,"a: ",a," b: ",b," c: ",c
Quit 1
}
Cube(num) PUBLIC {
Set result = num*num*num
Quit result
}
8.2.5.2 Passing By Reference
To pass by reference, specify a local variable name or the name of an unsubscripted array in the form:
.name
With passing by reference, a specified variable or array name does not have to exist before the function reference. Passing
by reference is the only way you can pass an array name to a function.
The period preceding the variable or array name is required. It distinguishes passing by reference from passing by value
using a variable name. If you specify a numeric literal that starts with a decimal point, the Caché ObjectScript compiler
correctly interprets it as a value rather than a reference.
In passing by reference, each variable or array name in the actual list is bound to the corresponding variable name in the
function’s formal list. Passing by reference provides an effective mechanism for two-way communication between the
referencing routine and the function. Any change that the function makes to a variable in its formal list is also made to the
Using Caché ObjectScript 83