From cc2b7a9a7b4c6269a6b93f99581b91b29fccc66d Mon Sep 17 00:00:00 2001
From: Anhgelus Morhtuuzh <william@herges.fr>
Date: Tue, 4 Nov 2025 12:19:54 +0100
Subject: feat(lexer): default grammar

---
 src/elixir_math_parser.yrl       | 44 ++++++++++++++++++++++++++++++++++++++++
 src/elixir_math_parser_lexer.xrl | 19 +++++++++++++++++
 2 files changed, 63 insertions(+)
 create mode 100644 src/elixir_math_parser.yrl
 create mode 100644 src/elixir_math_parser_lexer.xrl

diff --git a/src/elixir_math_parser.yrl b/src/elixir_math_parser.yrl
new file mode 100644
index 0000000..4900996
--- /dev/null
+++ b/src/elixir_math_parser.yrl
@@ -0,0 +1,44 @@
+Nonterminals
+  root
+  assignment
+  assignments
+  expr
+.
+
+Terminals
+  int
+  atom
+  '+'
+  '-'
+  '*'
+  '/'
+  '='
+.
+
+Rootsymbol
+   root
+.
+
+Right 100 '='.
+Left 300 '+'.
+Left 300 '-'.
+Left 400 '*'.
+Left 400 '/'.
+
+root -> assignments : '$1'.
+
+assignments -> assignment : '$1'.
+assignments -> assignment assignments : lists:merge('$1', '$2').
+
+assignment -> atom '=' expr : [{assign, '$1', '$3'}].
+
+expr -> int : unwrap('$1').
+expr -> atom : '$1'.
+expr -> expr '+' expr : {add_op, '$1', '$3'}.
+expr -> expr '-' expr : {sub_op, '$1', '$3'}.
+expr -> expr '*' expr : {mul_op, '$1', '$3'}.
+expr -> expr '/' expr : {div_op, '$1', '$3'}.
+
+Erlang code.
+
+unwrap({int, Line, Value}) -> {int, Line, list_to_integer(Value)}.
diff --git a/src/elixir_math_parser_lexer.xrl b/src/elixir_math_parser_lexer.xrl
new file mode 100644
index 0000000..a2980c8
--- /dev/null
+++ b/src/elixir_math_parser_lexer.xrl
@@ -0,0 +1,19 @@
+Definitions.
+INT        = [0-9]+
+NAME       = :[a-zA-Z_][a-zA-Z0-9_]*
+WHITESPACE = [\s\t\n\r]|;{2}
+
+Rules.
+\+            : {token, {'+',  TokenLine}}.
+\-            : {token, {'-',  TokenLine}}.
+\*            : {token, {'*',  TokenLine}}.
+\/            : {token, {'/',  TokenLine}}.
+\=            : {token, {'=',  TokenLine}}.
+{NAME}        : {token, {atom, TokenLine, to_atom(TokenChars)}}.
+{INT}         : {token, {int,  TokenLine, TokenChars}}.
+{WHITESPACE}+ : skip_token.
+
+Erlang code.
+% Given a ":name", chop off : and return name as an atom.
+to_atom([$:|Chars]) ->
+    list_to_atom(Chars).
-- 
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