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= Yapsi -- Yet Another Perl Six Implementation

This is an implementation of a Perl 6 compiler-and-runtime in Perl 6. It
currently runs off the old, pre-refactor branch of Rakudo known as 'alpha'.
You need to have an old version of Rakudo installed (say, the 2010-01
release), and available in your path under the name 'alpha'.

== Building Yapsi

This assumes that you have a working installation of alpha somewhere in
your $PATH. Yapsi currently works on top of alpha, an older branch of rakudo.
If you have not built alpha yet, please build it by doing a git clone from 
<git://> and "git checkout origin/alpha".

To build Yapsi:
    * type make in the directory where you've cloned Yapsi.
    * copy the generated lib/Yapsi.pir to $PERL6LIB or ~/.perl6/lib folder. 

== Features currently available in Yapsi

Right now you can do things like this:

$ ./yapsi -e 'say 42'

$ ./yapsi -e 'my $a; { $a = 5 }; say $a'

$ ./yapsi -e 'my $a = 5; my $b := $a; $b = 41; ++$b; say $a'

$ ./yapsi -e 'my $a = 42; while --$a { say $a }'

In other words, Yapsi currently handles declaration, immediate blocks,
assignment, binding, prefix increment/decrement, if/while, and say.

The compiler also detects use-before-declaration and syntax errors.

$ ./yapsi -e '$a; my $a'
Invalid. $a not declared before use

$ ./yapsi -e 'say say'
Could not parse

== Near-future directions

Things we hope to implement in the immediate future:

* More loops
* Function calls
* Phasers

== Raison d'être

Besides being useful as a p6-in-p6 implementation, Yapsi also might work as
a fast vehicle for exploring the following underexplored areas of the Perl 6

* Phasers
* Constant folding
* Early catching of errors
* Increased communication between compiler and runtime

== License

Yapsi is released under Artistic 2.0. See LICENSE.
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