META II is a domain specific language (DSL) for describing compilers. The META II compiler takes as input the DSL and outputs a compiler. The META II compiler can be described in this DSL.
Proposed by Dewey Val Schorre's 1965 paper META II: A Syntax-Oriented Compiler Writing Language
This implementation is based on Loup Vaillant's Meta II for Lua from http://loup-vaillant.fr/projects/metacompilers/
The META II compiler reads the DSL from standard input and writes the compiler (implemented in Lua) to standard output.
For example, to generate the compiler for arithemetic expressions, we can use the following pipeline:
cat examples/arithmetic.meta | lua meta.lua > examples/arithmetic.lua
Similarly the META II compiler is generated as follows:
cat meta.meta | lua meta.lua > meta2.lua
We can check that the output of the above (meta2.lua) is identical to meta.lua
.syntax program
output = '{'
* ( '$' {'io.write(_input)'}
| .string {'io.write(' $ ')'})
'}' {'io.write("\\n")' };
primary = .id { $ '()' }
| .string {'_run.testSTR(' $ ')' }
| '.id' {'local _input = _run.parse("^%a[%a%d]*")' }
| '.number' {'local _input = _run.parse("^%d+")'}
| '.string' {'local _input = _run.parseSTR()'}
| '.empty' {'_switch = true' }
| '(' choice ')'
| '*' {'repeat' }
primary {'until not _switch' }
{'_switch = true' };
sequence = {'repeat' }
(primary {'if not _switch then break end'} | output)
* (primary {'if not _switch then error() end'} | output)
{'until true'};
choice = {'repeat' }
sequence * ('|' {'if _switch then break end'} sequence)
{'until true'};
rule = .id {'function ' $ '()'} '=' choice ';' {'end'};
program = '.syntax' .id {'local _run = require("runtime")'}
* rule '.end' {$ '()' };
.end
Javascript: http://www.bayfronttechnologies.com/metaii.html
C: https://github.com/advancingdragon/meta
Forth and C: https://github.com/siraben/meta-yacc
C++: https://github.com/aburry/metaii
Uses Parsing Expression Grammar which allows for limited backtracking and allows predicates to be written in the host language. See http://www.tinlizzie.org/ometa/
Improves OMeta be separates the semantic actions from the parser. See https://github.com/harc/ohm