#try, #catch, #finally: Execution with Error Handling

Executes block1. If any exceptions are thrown, the #catch sections are searched for one where the type of exception matches the type element; if one is found, its block2 is run, if not the exception ‘escapes’. If a #finally section is present, block3 is always executed, after block1 and whichever block2 is run, if any.

Any number of #catch segments can be present; they are searched in order and therefore should grade from specific to general. You can stop any exceptions escaping by having a #catch $Exception {} section.

The exception caught is stored in #exception and is accessible within the #catch block. You can use #throw #exception to rethrow it (mimicing C#’s niladic throw).

For example:

#try {
 sr←$IO.File:OpenText(⍵);
 res←[""];
 #while{true} {
  thisline←sr:ReadLine();
  #if(thisline≡#null) { #break }
  #else {res,←thisline}
 }
} #catch $IO.FileNotFoundException {
 ⍇"File "+⍵+" was not found";
} #finally { sr:Close(); };