Shifted to stmt + SM

regression/Makefile

@@ -15,10 +15,10 @@ all: .depend $(TOPFILE).opt
 	$(OCAMLDEP) $(PXFLAGS) *.ml > .depend
 
 $(TOPFILE).opt: $(SOURCES:.ml=.cmx)
-	$(OCAMLOPT) -o $(TOPFILE).opt $(OFLAGS) $(LIBS:.cma=.cmxa) ostap.cmx Expr.cmx Embedding.cmx $(SOURCES:.ml=.cmx)
+	$(OCAMLOPT) -o $(TOPFILE).opt $(OFLAGS) $(LIBS:.cma=.cmxa) ostap.cmx Syntax.cmx Embedding.cmx SM.cmx $(SOURCES:.ml=.cmx)
 
 $(TOPFILE).byte: $(SOURCES:.ml=.cmo)
-	$(OCAMLC) -o $(TOPFILE).byte $(BFLAGS) $(LIBS) ostap.cmo Expr.cmo Embedding.cmo $(SOURCES:.ml=.cmo) 
+	$(OCAMLC) -o $(TOPFILE).byte $(BFLAGS) $(LIBS) ostap.cmo Syntax.cmo Embedding.cmo SM.cmo $(SOURCES:.ml=.cmo) 
 
 clean:
 	rm -Rf *.cmi *.cmo *.cmx *.annot *.o *.opt *.byte *~

regression/common.ml

@@ -1,5 +1,5 @@
 open GT
-open Expr
+open Syntax.Expr
 open Embedding
 
 let state ps = List.fold_right (fun (x, v) s -> update x v s) ps empty

src/Embedding.ml

@@ -4,14 +4,14 @@
 open GT
        
 (* Opening the substrate module for convenience. *)
-open Expr
+open Syntax
 
 (* Shortcuts for leaf constructors *)
-let ( ! ) x = Var x
+let ( ! ) x = Expr.Var x
-let ( !? ) n = Const n
+let ( !? ) n = Expr.Const n
 
 (* Implementation of operators *)
-let binop op x y = Binop (op, x, y)
+let binop op x y = Expr.Binop (op, x, y)
                          
 let ( +  ) = binop "+"
 let ( -  ) = binop "-"
@@ -27,14 +27,15 @@ let ( != ) = binop "!="
 let ( && ) = binop "&&"
 let ( || ) = binop "!!"
 
+let ( =:= ) x e = Stmt.Assign (x, e)
+let read  x = Stmt.Read x
+let write e = Stmt.Write e
+let (|>) x y = Stmt.Seq (x, y)
+                             
 (* Some predefined names for variables *)
 let x = !"x"
 let y = !"y"
 let z = !"z"
 let t = !"t"
 
-(* Voila; comment this out before submitting the solution *)
-let _ =
-  List.iter (fun e -> Printf.printf "eval s (%s) = %d\n" (show(expr) e) (eval s e)) [x+y*z- !?3; t-z+y && x]
-
                    

src/Expr.ml

@@ -1,54 +0,0 @@
-(* Simple expressions: syntax and semantics *)
-
-(* Opening a library for generic programming (https://github.com/dboulytchev/GT).
-   The library provides "@type ..." syntax extension and plugins like show, etc.
-*)
-open GT 
-             
-(* The type for the expression. Note, in regular OCaml there is no "@type..." 
-   notation, it came from GT. 
-*)
-@type expr =
-  (* integer constant *) | Const of int
-  (* variable         *) | Var   of string
-  (* binary operator  *) | Binop of string * expr * expr with show
-
-(* Available binary operators:
-    !!                   --- disjunction
-    &&                   --- conjunction
-    ==, !=, <=, <, >=, > --- comparisons
-    +, -                 --- addition, subtraction
-    *, /, %              --- multiplication, division, reminder
-*)
-
-(* State: a partial map from variables to integer values. *)
-type state = string -> int
-
-(* Empty state: maps every variable into nothing. *)
-let empty = fun x -> failwith (Printf.sprintf "Undefined variable %s" x)
-
-(* Update: non-destructively "modifies" the state s by binding the variable x 
-   to value v and returns the new state.
-*)
-let update x v s = fun y -> if x = y then v else s y
-
-(* An example of a non-trivial state: *)                                                   
-let s = update "x" 1 @@ update "y" 2 @@ update "z" 3 @@ update "t" 4 empty
-
-(* Some testing; comment this definition out when submitting the solution. *)
-let _ =
-  List.iter
-    (fun x ->
-       try  Printf.printf "%s=%d\n" x @@ s x
-       with Failure s -> Printf.printf "%s\n" s
-    ) ["x"; "a"; "y"; "z"; "t"; "b"]
-
-(* Expression evaluator
-
-     val eval : state -> expr -> int
- 
-   Takes a state and an expression, and returns the value of the expression in 
-   the given state.
-*)
-let eval = failwith "Not implemented yet"
-                    

src/Makefile

@@ -2,7 +2,7 @@ TOPFILE = rc
 OCAMLC = ocamlc
 OCAMLOPT = ocamlopt
 OCAMLDEP = ocamldep
-SOURCES = Expr.ml Embedding.ml
+SOURCES = Syntax.ml Embedding.ml SM.ml
 LIBS = GT.cma unix.cma re.cma re_emacs.cma re_str.cma
 CAMLP5 = -pp "camlp5o -I `ocamlfind -query GT.syntax` -I `ocamlfind -query ostap.syntax` pa_ostap.cmo pa_gt.cmo -L `ocamlfind -query GT.syntax`"
 PXFLAGS = $(CAMLP5)

src/SM.ml

@@ -0,0 +1,35 @@
+open GT       
+       
+(* The type for the stack machine instructions *)
+@type insn =
+(* binary operator                 *) | BINOP of string
+(* read to stack                   *) | READ
+(* write from stack                *) | WRITE
+(* load a variable to the stack    *) | LD    of string
+(* store a variable from the stack *) | ST    of string with show
+
+(* The type for the stack machine program *)                                                               
+type prg = insn list
+
+(* The type for the stack machine configuration: a stack and a configuration from statement
+   interpreter
+ *)
+type config = int list * Syntax.Stmt.config
+
+(* Stack machine interpreter
+
+     val eval : config -> prg -> config
+
+   Takes a configuration and a program, and returns a configuration as a result
+ *)                         
+let eval _ = failwith "Not yet implemented"
+
+(* Stack machine compiler
+
+     val compile : Syntax.Stmt.t -> prg
+
+   Takes a program in the source language and returns an equivalent program for the
+   stack machine
+ *)
+
+let compile _ = failwith "Not yet implemented"

src/Syntax.ml

@@ -0,0 +1,70 @@
+(* Opening a library for generic programming (https://github.com/dboulytchev/GT).
+   The library provides "@type ..." syntax extension and plugins like show, etc.
+*)
+open GT 
+    
+(* Simple expressions: syntax and semantics *)
+module Expr =
+  struct
+    
+    (* The type for expressions. Note, in regular OCaml there is no "@type..." 
+       notation, it came from GT. 
+    *)
+    @type t =
+    (* integer constant *) | Const of int
+    (* variable         *) | Var   of string
+    (* binary operator  *) | Binop of string * t * t with show
+
+    (* Available binary operators:
+        !!                   --- disjunction
+        &&                   --- conjunction
+        ==, !=, <=, <, >=, > --- comparisons
+        +, -                 --- addition, subtraction
+        *, /, %              --- multiplication, division, reminder
+    *)
+                                                            
+    (* State: a partial map from variables to integer values. *)
+    type state = string -> int 
+
+    (* Empty state: maps every variable into nothing. *)
+    let empty = fun x -> failwith (Printf.sprintf "Undefined variable %s" x)
+
+    (* Update: non-destructively "modifies" the state s by binding the variable x 
+      to value v and returns the new state.
+    *)
+    let update x v s = fun y -> if x = y then v else s y
+
+    (* Expression evaluator
+
+          val eval : state -> t -> int
+ 
+       Takes a state and an expression, and returns the value of the expression in 
+       the given state.
+    *)
+    let eval _ = failwith "Not implemented yet"
+
+  end
+                    
+(* Simple statements: syntax and sematics *)
+module Stmt =
+  struct
+
+    (* The type for statements *)
+    @type t =
+    (* read into the variable           *) | Read   of string
+    (* write the value of an expression *) | Write  of Expr.t
+    (* assignment                       *) | Assign of string * Expr.t
+    (* composition                      *) | Seq    of t * t with show
+
+    (* The type of configuration: a state, an input stream, an output stream *)
+    type config = Expr.state * int list * int list 
+
+    (* Statement evaluator
+
+          val eval : config -> t -> config
+
+       Takes a configuration and a statement, and returns another configuration
+    *)
+    let eval _ = failwith "Not implemented yet"
+                                                         
+  end