diff options
| -rw-r--r-- | perl6.html.markdown | 33 |
1 files changed, 29 insertions, 4 deletions
diff --git a/perl6.html.markdown b/perl6.html.markdown index 4e7d8c6e..d12b99ae 100644 --- a/perl6.html.markdown +++ b/perl6.html.markdown @@ -700,15 +700,37 @@ try { open 'foo'; CATCH { when X::AdHoc { say "unable to open file !" } - # any other exception will be re-raised, since we don't have a `default` + # Any other exception will be re-raised, since we don't have a `default` + # Basically, if a `when` matches (or there's a `default`) marks the exception as + # "handled" so that it doesn't get re-thrown from the `CATCH`. + # You still can re-throw the exception (see below) by hand. } } # You can throw an exception using `die`: die X::AdHoc.new(payload => 'Error !'); -# TODO warn -# TODO fail -# TODO CONTROL + +# You can access the last exception with `$!` (usually used in a `CATCH` block) + +# There are also some subtelties to exceptions. Some Perl 6 subs return a `Failure`, +# which is a kind of "unthrown exception". They're not thrown until you tried to look +# at their content, unless you call `.Bool`/`.defined` on them - then they're handled. +# (the `.handled` method is `rw`, so you can mark it as `False` back yourself) +# +# You can throw a `Failure` using `fail`. Note that if the pragma `use fatal` is on, +# `fail` will throw an exception (like `die`). +fail "foo"; # We're not trying to access the value, so no problem. +try { + fail "foo"; + CATCH { + default { say "It threw because we try to get the fail's value!" } + } +} + +# There is also another kind of exception: Control exceptions. +# Those are "good" exceptions, which happen when you change your program's flow, +# using operators like `return`, `next` or `last`. +# You can "catch" those with `CONTROL` (not 100% working in Rakudo yet). ### Packages # Packages are a way to reuse code. Packages are like "namespaces", and any @@ -1351,6 +1373,9 @@ so 'ayc' ~~ / a [ b | y ] c /; # `True`. Obviously enough ... # Note: the first-matching `or` still exists, but is now spelled `||` 'foo' ~~ / fo || foo /; # `fo` now. + + + ### Extra: the MAIN subroutime # The `MAIN` subroutine is called when you run a Perl 6 file directly. # It's very powerful, because Perl 6 actually parses the argument |