Vocabulary/trydot

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try.
catch.
catchd.
catcht.
Execute with error path
Error path
Error path only if not debugging
Catch throw. from called function
Control

Valid only inside an explicit definition.


You put sentences into a try. structure when you want to recover if they fail. If there is an error in the block following try., the try. is aborted and control passes to the catch./catchd., with catchd. being ignored if debugging is on. catcht. is a special case and picks up the special error case created by a throw. control word.

try. continues execution with the sentence following the try.. If an error is encountered, control passes to one of the catch blocks:

  1. If the error is uncaught throw., in other words if throw. was executed in a called function and has not already been intercepted, and there is a catcht. block in the current try.structure, control passes to the first sentence of the catcht. block and the error is reset.
  2. Otherwise, if there is a catch. block, control passes to the first sentence of the catch. block and the error is reset.
  3. Otherwise, if there is a catchd. block and debugging has not been turned on, control passes to the first sentence of the catchd. block and the error is reset.

catchd. is used for code that provides a general-purpose error handler whose purpose is to catch errors and keep going. If you want to debug one of those errors, you turn on the debugger and then the catchd. has no effect, and your program will stop at the error so that you can look around.