diff --git a/flap/src/hopix/hopixLexer.mll b/flap/src/hopix/hopixLexer.mll
index 980c832..5e6312e 100644
--- a/flap/src/hopix/hopixLexer.mll
+++ b/flap/src/hopix/hopixLexer.mll
@@ -15,18 +15,35 @@
 }
 
 let newline = ('\010' | '\013' | "\013\010")
-
 let blank   = [' ' '\009' '\012']
 
 let digit = ['0'-'9']
+let hexa = "0x" ['0'-'9' 'a'-'f' 'A'-'F']
+let bina = "0b" ['0'-'1']
+let octa = "0o" ['0'-'7']
 
+let integers = '-'? (digit+
+             | hexa+
+             | bina+
+             | octa+)
+
+let ident = ['a'-'z']['A'-'Z' 'a'-'z' '0'-'9' '_']*
 
 rule token = parse
   (** Layout *)
   | newline         { next_line_and token lexbuf }
   | blank+          { token lexbuf               }
-  | eof             { EOF       }
+  | eof             { EOF                        }
 
-  (** Lexing error. *)
+  (** Keywords *)
+  | "let"           { LET                        }
+
+  (** Operators *)
+  | '='             { EQUAL                      }
+
+  (** Values *)
+  | integers as i   { INT (Mint.of_string i)     }
+  | ident as s      { ID s                       }
+
+  (** Lexing error *)
   | _               { error lexbuf "unexpected character." }
-
diff --git a/flap/src/hopix/hopixParser.mly b/flap/src/hopix/hopixParser.mly
index 9d94e29..14a8a6e 100644
--- a/flap/src/hopix/hopixParser.mly
+++ b/flap/src/hopix/hopixParser.mly
@@ -3,20 +3,46 @@
   open HopixAST
   open Position
 
-
 %}
 
-%token EOF
+%token EOF LET EQUAL
 
+%token<Mint.t> INT
+%token<string> ID
 
 %start<HopixAST.t> program
 
 %%
 
-program: EOF
-{
-   []
-}
+program:
+| definition=located(definition)* EOF {
+    definition
+  }
+
+definition:
+| v=vdefinition {
+    DefineValue v
+  }
+
+vdefinition: // manque le type ici, on met None en attendant
+| LET i=located(identifier) EQUAL e=located(expression) {
+    SimpleValue(i, None, e)
+  }
+
+expression:
+| l=located(literal) {
+    Literal l
+  }
+
+literal:
+| i=INT {
+    LInt i
+  }
+
+identifier:
+| i=ID {
+    Id i
+  }
 
 %inline located(X): x=X {
   Position.with_poss $startpos $endpos x