attl

attl

A Tiny Tool Language.

Attl is a TCL-like embedded scripting language implemented in Go.# ATTL

Introduction

Attl is A Tiny Tool Language, an embeddable, interpreted scripting language, implemented in Go, that somewhat resembles TCL and shell scripts, but with typed values, and LISP like semantics.

One notable feature is that the language itself has no key words, nor flow control by itself, but that this is provided by the commands that ATTL executes. This makes it possible to disable certain commands, or example, in case where it is desirable for the script to be not Turing complete.

The syntax is extremelty simple, and based on a rescursive descent LL1 parser, where the parser only considers the next character and the current state of parsing to deterine the meaning of the code. Code that is easy to parse by the computer is easy to understand by humans also, which is why the limitations of LL1 parsing are acceptable.

Grammar

The formal grammar of ATTL is as follows:

SCRIPT -> STATEMENTS . STATEMENTS -> STATEMENT OPTSTATEMENTS . OPTSTATEMENTS -> rs STATEMENT OPTSTATEMENTS | . STATEMENT -> OPTWS EXPRESSION . EXPRESSION -> COMMAND | BLOCK | comment | . OPTWS -> ws | . COMMAND -> ORDER PARAMETERS . ORDER -> LITERAL | EVALUATION . BLOCK -> ob STATEMENTS cb . PARAMETERS -> ws PARAMETER OPTPARAMETERS | . PARAMETER -> LITERAL | BLOCK | GETTER | EVALUATION | . EVALUATION -> oe COMMAND ce . GETTER -> get TARGET . TARGET -> GETTER | LITERAL . LITERAL -> word | string | integer . rs -> /[\n\r]+/ . ws -> /[\t ]+/ . word -> /[^ \t\n\$(){}][]+/ string -> /"[^"]+"/ | /[^]+`/ integer -> [+-]?[0-9]+ comment -> /#[^\n]+\n/ . get -> '$' . oe -> '[' . ce -> ']' . ob -> '{' . cb -> '}' .