On Jul 9, 2015 11:04 AM, "Egor Skriptunoff" <egor.skriptunoff@gmail.com> wrote:
>
> Hi!
>
> The following "proposals" are just for fun.
>
> -----------------------------
> 1) A must-have "dont" statement :-)
>
> dont
> -- code inside dont..end block will be skipped
> -- useful for easy commenting do..end block
> end
>
> "dont" is also applicable to any block: if, while, for, multiline assignment, function definition, etc.
>
> dont if ... then -- this condition will not be evaluated
> -- this code will be skipped
> else
> -- this code will be skipped too
> end
>
> "dont" statement acts as --[[...]] comment, but only for a single statement inside
> When using "dont" we do not need to search for a place where very long statement ends, so using "dont" is more easy than --[[...]]
> The "dont...end" is a syntactic sugar for "dont do...end"
>
> -----------------------------
> 2) Famous "comefrom" operator as the opposite to "goto"
>
> ...
> ::label1::
> ...
> comefrom label1, label2, label3
> ...
> ::label2::
> ...
> ::label3::
> ...
>
> is equivalent to
>
> ...
> goto label0
> ...
> ::label0::
> ...
> goto label0
> ...
> goto label0
> ...
>
> -----------------------------
> 3) Labels are considered to be first-class citizens
>
> ::Label1::
> ...
> local my_label = Label1 -- assigning a value of type "label" to a variable
> ...
> -- Now "goto" operator gets its real power!
> goto my_array_of_labels[where_do_you_want_to_go_today]
> ...
> -- And of course the same is true for "comefrom" :-)
> comefrom get_some_labels()
> -- it is equivalent to "comefrom label1, label2,..."
> -- where label1, label2,.. are values returned by LAST invocation of get_some_labels()
> -- "comefrom" without labels is valid (it just does nothing useful)
> ...
>
> -----------------------------
> 4) Program can modify its own body using methods of labels
> A label is a "bookmark" between statements in a program (or before first statement or after last statement)
> A label may be named (defined at compile time) or unnamed (created at runtime)
>
> ...
> some_func(some_params)
> ...
> -- standard library function to create unnamed label just before current statement
> local here = labels.this_label()
> -- create label just before some_func invocation
> local previous_some_func_invocation = here:search_nearest("backward", "call", "some_func")
> -- replace "some_func()" with "another_func()" in the program body
> previous_some_func_invocation:replace_statement("another_func()")
> ...
> -- go to unnamed label
> goto previous_some_func_invocation
> ...
>
> -----------------------------
> The source of craziness:
> www.modell.com/Magery/SPharmful.html
>
> -- Egor
>
Computed goto isn't *that* crazy. It's how things like jump tables and switch statements are implemented. Lua doesn't really *need* them though since it has first class functions.
