From 7dcb51ab0ec2dadd3728a3872a56cb64c1e0c23a Mon Sep 17 00:00:00 2001
From: colin <colin@cicadas.surf>
Date: Thu, 3 Aug 2023 06:39:48 -0700
Subject: Add initial readme

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+* Argot: A System For Grammar-Driven Macros
+
+The ~argot~ system provides a macro-defining-macro called
+~deflanguage~. The ~deflanguage~ macro accepts a context-free grammar,
+augmented with parse handlers, and defines a macro whose body is
+parsed and expanded according to that augmented grammar.
+
+** A brief tour
+
+In ~/examples/calc.lisp~ you see the following ~deflanguage~:
+
+#+begin_src lisp
+
+(deflanguage calc (:documentation "A calculator language")
+  (<start>
+   :match (:or
+           (:seq <subexpr> (:eof))
+           (:seq <value> (:eof))
+           (:seq <unop> (:eof))
+           (:seq <binop> (:eof)))
+   :then car)
+  (<expr>
+   :match (:or <subexpr> <value> <unop> <binop>))
+  (<subexpr>
+   :match (:{} calc))
+  (<value>
+   :match (:item)
+   :if numberp)
+  (<binop>
+   :match (:seq
+            (:@ lhs <expr>)
+            (:@ rhs (:+ (:seq (:or= + - / * ^ %) <expr>))))
+   :then (expand-binop lhs rhs))
+  (<unop>
+   :match (:seq (:or= sin cos tan -) <expr>)))
+
+#+end_src
+
+This defines a cacluator language that you can use like so:
+
+#+begin_src lisp
+
+> (calc 1)
+1
+> (calc 1 + 2 + 3)
+6
+> (calc 1 + 2 * 3)
+7
+> (calc (1 + 2) * 3)
+9
+> (calc (1 + 2) * 3 + 1)
+10
+> (calc (1 + 2) * (3 + 1))
+12
+> (calc 2 ^ (2 * (1 + 1)))
+16
+
+#+end_src
+
+The symbol ~calc~ also has a function docstring. If you are in slime,
+you can evoke ~M-x slime-documentation~ with your cursor over the
+~calc~ symbol and see this:
+
+#+begin_src
+
+Documentation for the symbol CALC:
+
+Function:
+ Arglist: (&BODY TOKENS)
+
+ A calculator language
+
+<START>         ::= (<SUBEXPR> ::EOF:: | <VALUE> ::EOF:: | <UNOP> ::EOF:: | <BINOP> ::EOF::)
+<EXPR>          ::= (<SUBEXPR> | <VALUE> | <UNOP> | <BINOP>)
+<SUBEXPR>       ::= {CALC}
+<VALUE>         ::= ::TOKEN::
+<BINOP>         ::= <EXPR> ('+' | '-' | '/' | '*' | '^' | '%') <EXPR>⁤+
+<UNOP>          ::= ('SIN' | 'COS' | 'TAN' | '-') <EXPR>
+
+KEY: 
+::TOKEN::  Any ole token
+::EOF::    Explicitly match the end of the input
+{GRAMMAR}  Parse a sublist of tokens with GRAMMAR
+(a|b|..)   One of the alternavites a b ...
+PATTERN+   One or more PATTERN
+PATTERN*   Zero or more PATTERN
+<RULE>     A nonterminal symbol - naming a parse rule
+[OPT]      Zero or one of OPT
+
+#+end_src
+
+** User Guide
+
-- 
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