control structure
always
You can use always
to identify code that will run regardless of whether a throw
occurs.
The always
keyword begins a block of code that will be executed at the end of a lexical scope. Only a halt-everything
will cause the always block not to be executed. The code in the always block is executed at the end of the scope, even if a something occurs which would otherwise cause the scope to terminate. The always
block will be executed even if you exit the scope with a throw
, return
, exit
, or halt
.
The always block must be the last block in a lexical scope, occurring after any catch
blocks in the scope. In this example, the reopen
action will throw to #external-exception if the stream "main-log" is not initialized.
include "omdate.xin" global stream main-log ;set from command line process local stream log-stream reopen log-stream as file main-log put log-stream "The program ran at: " || date "=xY-=M-=D =h:=m:=s" || "%n" catch #program-error output "Something went wrong. Don't know what it was.%n" always put #error "The program terminated at: " || date "=xY-=M-=D =h:=m:=s" || "%n"
You may want to include more than one always block in a scope. If an error or throw occurs in an always block, the rest of that block will not be executed, but a subsequent always
block in the same scope will be executed. This allows you to make sure that each always operation is executed, even if there is an error in executing a previous one.
When a throw is initiated in a nested scope and caught at an outer level of nesting, code is executed in the following sequence: