B.4  Looping

loop-related features

• do/loop -- beginning and end of an infinite loop block
• do/end do -- beginning and end of a one iteration loop block
• exit do -- get out of a loop block
• repeat do -- repeat the code within the loop block
• while xxx -- where xxx evaluates to TRUE or FALSE, loops while xxx is true
• until xxx -- where xxx evaluates to TRUE or FALSE, loops until xxx is true

Both while and until can occur anywhere within a loop and can occur more than once.

• for varname = start_value to end_value / next varname
• for varname = start_value to end_value step step_value / next varname
• repeat for -- repeat the current iteration -- the varname is not adjusted
• iterate for -- start the next iteration
• exit for -- get out of this for/next block

The while and until statements can appear anywhere inside of a do/loop and can even appear multiple times with different conditions.