Error Messages/40616

Error Message Examples

You cannot assign to a slice or subscript of a global variable object.

Cause

You are trying to assign a value to a slice (subscripted element) of a global variable. This is not permitted, since it would contravene Analytica's general principle of no side-effects. You may assign to a slice of a local variable.

This example triggers this error. Here BadDef tries to assign to a slice of the global variable X:

Index I := 1..9

Variable X := Table(I)(7, 8, 3, 2, 5, 4, 9, 1, 5)

Variable BadDef := (X[I = 5] := 99)

Remedies

You may assign to a global variable in a Button script or in a Function called from a Button script Scripts and Buttons, directly or indirectly. The rationale is that this does not violate the No-side effects principle because clicking a button means the user is causing the effect directly.

You can often work around this issue by copying the global array into a local, assigning to a slice of the array, and then assigning the local back to the global within a function called from a Button script. For example, suppose you want to assign 999 to the 10th element over I of global variable X. If you define a variable 

  Variable TrytoAssignX := X[I=10] := 999

it will give the error above. So instead define 

  Function AssigntoX(v)
  Definition: Variable local_X:= X;
       local_X[i=10] := v;
       X := local_X
  Button Assign_to_X
  Script:  Assign_to_X(999)

When you press the button, it will call Assign_to_X(999) and make the assignment.



You are not allowed to post comments.

Comments
<comments />