In this module, we will delve into advanced control structures in MUMPS (M). These structures allow for more sophisticated flow control in your programs, enabling you to write more efficient and readable code.

1. Nested Control Structures
2. Switch-like Constructs
3. Loop Control with QUIT and CONTINUE
4. Error Trapping and Handling

Nested control structures allow you to place one control structure inside another. This is useful for handling complex decision-making processes.

• The outer IF checks condition1.
• If condition1 is true, the inner IF checks condition2.
• Depending on the result of condition2, different messages are printed.

Write a nested IF statement that checks three conditions and prints a unique message for each possible combination of true/false values.

MUMPS does not have a built-in SWITCH statement, but you can achieve similar functionality using IF and ELSE statements.

• The variable option is checked against multiple values.
• Depending on the value of option, a different message is printed.

Simulate a SWITCH statement that handles five different cases and prints a unique message for each case.

MUMPS provides QUIT and CONTINUE commands to control the flow within loops.

• The FOR loop runs from 1 to 10.
• The QUIT command exits the loop when i equals 5.
• The CONTINUE command skips the current iteration if i is even.

Write a FOR loop that prints numbers from 1 to 20 but skips multiples of 3 and stops the loop when the number is greater than 15.

Error trapping allows you to handle errors gracefully without crashing your program.

• $ZTRAP is set to jump to LABEL when an error occurs.
• The division by zero error triggers the error handler.
• The error handler prints the error message stored in $ZERROR.

Create an error handler that catches any error, logs the error message to a global variable, and then continues execution.

In this module, we covered advanced control structures in MUMPS, including nested control structures, switch-like constructs, loop control with QUIT and CONTINUE, and error trapping and handling. These tools will help you write more robust and efficient MUMPS programs.

Next, we will explore error handling and debugging in more detail in the following module.