Revisions for untitled paste

@@ -0,0 +1,2 @@

+all:
+        flex -o lex.yy.cpp scanner.lpp && bison -do parser.tab.cpp parser.ypp && clang++-7 -std=c++17 lex.yy.cpp parser.tab.cpp
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@@ -0,0 +1,121 @@

+%skeleton "glr.cc"
+
+%define parse.error verbose
+
+%code requires
+{
+#include <memory>
+#include <variant>
+
+class tup;
+
+using expr = std::variant<int, std::unique_ptr<tup>, std::unique_ptr<tup>, std::unique_ptr<tup>, std::unique_ptr<tup>>;
+
+class tup
+{
+public:
+  expr a;
+  expr b;
+};
+}
+
+%code provides
+{
+#define YY_DECL int yylex (yy::parser::semantic_type *yylval)
+YY_DECL;
+}
+
+%code top
+{
+#include <iostream>
+}
+
+%define api.value.type union
+
+%token <int> NUMBER
+
+%%
+
+_start:
+  expr
+    {
+      
+    }
+
+%type <expr *> expr;
+
+expr:
+  product
+    {
+      $$ = $1;
+    }
+| expr '+' product
+    {
+      // Some code
+    }
+| expr '-' product
+    {
+      // Some code
+    }
+
+%type <expr *> product;
+
+product:
+  prim
+    {
+      $$ = $1;
+    }
+| product '*' prim
+    {
+      // Some code
+    }
+| product '/' prim
+    {
+      // Some code
+    }
+
+%type <expr *> prim;
+
+prim:
+  NUMBER
+    {
+      // Some code
+    }
+| '(' expr ')'
+    {
+      $$ = $2;
+    }
+
+%%
+
+void
+yy::parser::error (const std::string &m)
+{
+  std::cerr << m << "\n";
+}
+
+int
+main (void)
+{
+  try
+    {
+      yy::parser p;
+
+      if (p.parse () != 0)
+        {
+          return EXIT_FAILURE;
+        }
+
+      return EXIT_SUCCESS;
+    }
+  catch (const std::exception &e)
+    {
+      std::cerr << "Exception from main: " << e.what () << "\n";
+      return EXIT_FAILURE;
+    }
+  catch (...)
+    {
+      std::cerr << "Exception from main\n";
+      return EXIT_FAILURE;
+    }
+}
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@@ -0,0 +1,30 @@

+%option noyywrap
+%option warn nodefault
+
+%{
+#include <stdlib.h>
+
+#include <string>
+
+#include "parser.tab.hpp"
+%}
+
+%%
+
+[-+*/()]* {
+  return yytext[0];
+}
+
+[0-9][0-9]* {
+  yylval->NUMBER = atoi (yytext);
+  return yy::parser::token::NUMBER;
+}
+
+[ \t\n]+ {
+}
+
+. {
+  abort ();
+}
+
+%%
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