Add production rules that seem to work

parser.y

@@ -2,6 +2,7 @@
 
 #include <string>
 #include <iostream>
+#include <set>
 #include "parser.hpp"
 
 %}
@@ -51,25 +52,87 @@ void yyerror(const char* s) {
     std::cout << s << std::endl;
 }
 
+std::set<std::string> varset;
+
 %}
 
 %%
 
 program
-    : program stmt
+    : stmts
+    ;
+
+stmts
+    : stmts stmt
     | stmt
     ;
 
 stmt
-    : expr NEWLINE;
+    : expr NEWLINE
+    | if
+    | while
+    | BREAK NEWLINE
+    ;
 
 expr
     : assign
-    | INTEGER
+    | eq
+    ;
+
+while
+    : WHILE expr COLON NEWLINE block
+    ;
+
+if
+    : IF expr COLON NEWLINE block ifend
+    | IF expr COLON NEWLINE block
+    ;
+
+ifend
+    : ELIF expr COLON NEWLINE block ifend
+    | ELIF expr COLON NEWLINE block
+    | ELSE COLON NEWLINE block
+
+block
+    : INDENT stmts DEDENT
     ;
 
 assign
     : IDENTIFIER ASSIGN expr
     ;
 
+eq
+    : eq EQ rel
+    | eq NEQ rel
+    | rel
+    ;
+
+rel
+    : rel LT sum
+    | rel LTE sum
+    | rel GT sum
+    | rel GTE sum
+    | sum
+    ;
+
+sum
+    : sum PLUS factor
+    | sum MINUS factor
+    | factor
+    ;
+
+factor
+    : factor TIMES term
+    | factor DIVIDEDBY term
+    | term
+    ;
+
+term
+    : IDENTIFIER
+    | FLOAT
+    | INTEGER
+    | BOOLEAN
+    | LPAREN expr RPAREN
+    ;
+
 %%