What is flow control and the exit statement in Euphoria?

What is flow control?

Flow control is the process of breaking the default order of a program statement’s execution. The default behavior of a program’s execution flow is to automatically run the next program after the current one. Flow control, however, allows us to set up a custom execution order for any execution block in our code.

The Euphoria language provides simple program structures or statements for flow control, such as exit, break, continue, retry, with entry, and goto.

This shot focuses on the exit statement.

What is the exit statement?

The exit statement causes the flow of a program to immediately terminate the loop, and continues the program execution with the first statement after the end of the loop.

Wherever the exit statement is placed in a loop during program execution, the loop exits, and the normal code flow recommences.

Code

The code below contains a loop that exits at some point if the condition is met.

Note: We need to include the std/math.e file in our program.

include std/math.e
atom x = 2, y = 10, z = 5
for i = x to y do
    
    if z = i then
       printf(1,"this works \n") 
       
       exit -- if true stop executing code inside the 'for' block.
             if z < y then
                printf(1,"does not")
             end if
    end if
    
       
end for
-- Flow restarts here.
if z > x then 
 printf(1,"\n The execution flow has recommenced")
 end if

Explanation

The for block will exit if the first if condition returns true. This means that the code contained in the second if block will not run. Instead, we execute the rest of the program below the for loop.

  • Line 1: We include the std/math.e file.
  • Line 3: We declare variables and assign values.
  • Line 4: We start the for loop that extends until line 16.
  • Lines 6 to 13: This contains some if statements that are the codes to be executed when the for loop runs.
  • Line 9: This is where the exit statement is used to exit the program when the if condition on line 6 evaluates to true.
  • Line 10: The if condition on this line executes if the exit statement is not stated right above it.
  • Line 19: The normal flow of execution in the program recommences, after the for loop exits on line 18. An if loop starts, and it ends on line 21.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)