refactor: Syntax with unit tests

lib/analyzer/parser.mly

@@ -0,0 +1,53 @@
+%{
+open Syntax
+%}
+
+%token <int> INT
+%token PLUS "+"
+%token MINUS "-"
+%token TIMES "*"
+%token DIV "/"
+
+%token SEMICOLON ";"
+
+%token LPAREN "("
+%token RPAREN ")"
+
+%token EOF
+
+%left PLUS MINUS
+%left TIMES DIV
+
+%nonassoc UMINUS
+
+%start <SourceFiles.source_files> main
+
+%%
+
+main:
+  | statements EOF { SourceFiles.SourceFile $1 }
+
+statements:
+  | statement ";"            { $1 }
+  | statement ";" statements { Statements.SequenceStatement ($1, $3) }
+
+statement:
+  | expression  { Statements.ExpressionStatement($1) }
+
+expression:
+  | literal            { Expressions.Literal($1) }
+  | unary_expression   { $1 }
+  | binary_expression  { $1 }
+  | "(" expression ")" { $2 }
+
+literal:
+  | INT { Literals.Integer($1) }
+
+unary_expression:
+  | "-" expression %prec UMINUS { Expressions.UnaryExpression(UnaryOperators.ArithmeticNegation, $2) }
+
+binary_expression:
+  | expression "+" expression { Expressions.BinaryExpression (BinaryOperators.Add, $1, $3) }
+  | expression "-" expression { Expressions.BinaryExpression (BinaryOperators.Subtract, $1, $3) }
+  | expression "*" expression { Expressions.BinaryExpression (BinaryOperators.Multiply, $1, $3) }
+  | expression "/" expression { Expressions.BinaryExpression (BinaryOperators.Divide, $1, $3) }