Notes About Using Subroutines; Avoiding Circular-Definition Errors; Controlling The Flow Of A Function Or Program - Texas Instruments TI-NSPIRE Software Manual

Notes about using subroutines

At the end of a subroutine, execution returns to the calling program. To
exit a subroutine at any other time, use
A subroutine cannot access local variables declared in the calling
program. Likewise, the calling program cannot access local variables
declared in a subroutine.
commands are local to the programs in which they are located.
Lbl
Therefore, a
Goto
label in a subroutine or vice versa.

Avoiding circular-definition errors

When evaluating a user-defined function or running a program, you can
specify an argument that includes the same variable that was used to
define the function or create the program. However, to avoid circular-
definition errors, you must assign a value for variables that are used in
evaluating the function or running the program. For example:
À
x+1 x
&
– or –
For i,i,10,1
À
Disp i
EndFor
À
Causes a
Circular definition
value. The error does not occur if x or i has already been assigned a
value.

Controlling the flow of a function or program

When you run a program or evaluate a function, the program lines are
executed in sequential order. However, some commands alter the
program flow. For example:
• Control structures such as
to decide which part of a program to execute.
• Loop commands such as
334
command in the calling program cannot branch to a
error message if x or i does not have a
If...EndIf
For...EndFor
with no argument.
Return
commands use a conditional test
repeat a group of commands.
Programming