Add is_nat operator to PascaLIGO

src/passes/operators/operators.ml

@@ -64,6 +64,7 @@ module Simplify = struct
       ("size" , "SIZE") ;
       ("int" , "INT") ;
       ("abs" , "ABS") ;
+      ("is_nat", "ISNAT") ;
       ("amount" , "AMOUNT") ;
       ("balance", "BALANCE") ;
       ("now" , "NOW") ;
@@ -511,6 +512,10 @@ module Typer = struct
     let%bind () = assert_t_int t in
     ok @@ t_nat ()
 
+  let is_nat = typer_1 "ISNAT" @@ fun t ->
+    let%bind () = assert_t_int t in
+    ok @@ t_option (t_nat ()) ()
+
   let neg = typer_1 "NEG" @@ fun t ->
     let%bind () = Assert.assert_true (eq_1 t (t_nat ()) || eq_1 t (t_int ())) in
     ok @@ t_int ()
@@ -775,6 +780,7 @@ module Typer = struct
       get_entrypoint ;
       neg ;
       abs ;
+      is_nat ;
       cons ;
       now ;
       slice ;
@@ -844,6 +850,7 @@ module Compiler = struct
     ("ASSERT" , simple_unary @@ i_if (seq [i_push_unit]) (seq [i_push_unit ; i_failwith])) ;
     ("INT" , simple_unary @@ prim I_INT) ;
     ("ABS" , simple_unary @@ prim I_ABS) ;
+    ("ISNAT", simple_unary @@ prim I_ISNAT) ;
     ("CONS" , simple_binary @@ prim I_CONS) ;
     ("UNIT" , simple_constant @@ prim I_UNIT) ;
     ("BALANCE" , simple_constant @@ prim I_BALANCE) ;

src/test/contracts/isnat.ligo

@@ -0,0 +1,2 @@
+function main (const i: int) : option(nat) is
+ block {skip} with is_nat(i)

src/test/integration_tests.ml

@@ -1211,6 +1211,20 @@ let balance_constant_mligo () : unit result =
   let input = e_tuple [e_unit () ; e_mutez 0]  in
   let expected = e_tuple [e_list []; e_mutez 4000000000000] in
   expect_eq program "main" input expected
+
+let is_nat () : unit result =
+  let%bind program = type_file "./contracts/isnat.ligo" in
+  let%bind () = 
+    let input = e_int 10 in
+    let expected = e_some (e_nat 10) in
+    expect_eq program "main" input expected
+  in
+  let%bind () =
+    let input = e_int (-10) in
+    let expected = e_none () in
+    expect_eq program "main" input expected
+  in ok ()
+
 let simple_access_ligo () : unit result =
   let%bind program = type_file "./contracts/simple_access.ligo" in
   let make_input = e_tuple [e_int 0; e_int 1] in
@@ -1313,6 +1327,7 @@ let main = test_suite "Integration (End to End)" [
     test "let multiple (mligo)" mligo_let_multiple ;
     test "balance constant" balance_constant ;
     test "balance constant (mligo)" balance_constant_mligo ;
+    test "is_nat" is_nat ;
     test "simple_access (ligo)" simple_access_ligo;
     test "deep_access (ligo)" deep_access_ligo;
     test "entrypoints (ligo)" entrypoints_ligo ;