spicy (two) unit hooks

unit hooks, the hook.Used to control parsing, track status and retrieve results.is the block of code that triggers execution during parsing and has access to the current unit instance.

Hooks are similar to functions: they are bodies that execute when triggered. These bodies can receive a set of input parameters, but unlike functions, a hook can have multiple bodies.If multiple body implementations are provided for the same hook, they will be executed in sequence.

The 7 most commonly used hooks:

# Start execution before unit parsingon %init() { ... }# Execute after unit parsing is completeon %done { ... }# Executed when a parsing error is encountered, just before the parser aborts processingon %error { ... }# Executed after cell parsing is done in any way.This hook is most useful for modifying global state that needs to be updated, regardless of whether the parsing process was successful or not.This hook is also guaranteed to execute eventually once %init fires.It will run after %done or %error respectively.(If a new error occurs during the execution of %finally, the unit's %error hook will not be triggered.)on %finally { ... }#on %print { ... }# Executed immediately after parsing the given unit field.The parsed value can be accessed via $$, possibly with any relevant type conversions applied (see Dynamic type conversions using &convert).The same content has also been assigned to this field.on  { ... } (field hook)# Assuming the specified field is a container (eg, a vector), this is executed each time a new container element is parsed, and just before it is added to the container.The parsed element can be accessed via the $$ identifier and can be modified before being stored.Hook implementations can also use the stop statement to abort container resolution without adding the current element.on  foreach {