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
While you may not normally assign to a global variable, either directly or to a slice of the variable, in the definition of a variable, you may assign to a global variable (but not to a slice) in a Button script or in a Function called from a Button script Scripts and Buttons. The latter does not violate the No-side effects principle because by clicking a button the user causes the effect directly.
You can often work around the prohibition against slice assignment by writing a function, F, that
- copies the global array, X, into a local variable, local_x,
- assigns to a slice of the array, local_x, and then
- assigns the value of local_x back to the global, X,
- and finally, cal function F from a Button script.
For example, suppose you want to assign 999 to the 5th element over index I of global variable X:
Function Assign_to_X(v)
Definition:
Variable local_x := X;
local_x[I=5] := v;
X := local_x
Button Do_Assign
Script: Assign_to_X(999)
When you press the button, Do_Assign, it calls Assign_to_X(999) and completes the slice assignment.
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