Standard ML of New Jersey (32-bit) v110.99 [built: Thu Dec 24 11:01:10 2020]
- fun f1 x = 1 + hd x;
val f1 = fn : int list -> int
- f1 [1,2,3]
= ;
val it = 2 : int
-
-
- fun f1 x :: xs = 1 + x;
stdIn:6.10-6.12 Error: infix operator "::" used without "op" in fun dec
stdIn:6.10-6.12 Error: data constructor :: used without argument in pattern
-
-
- fun f1 (x :: xs) = 1 + x;
stdIn:8.5-8.25 Warning: match nonexhaustive
          x :: xs => ...

val f1 = fn : int list -> int
-
-
- fun f1 x = 1 + hd x;
val f1 = fn : int list -> int
- f1 [];

uncaught exception Empty
  raised at: smlnj/init/pervasive.sml:193.19-193.24
-
-
- fun f1 (x :: xs) = 1 + x;
stdIn:14.5-14.25 Warning: match nonexhaustive
          x :: xs => ...

val f1 = fn : int list -> int
- f1 [];

uncaught exception Match [nonexhaustive match failure]
  raised at: stdIn:14.25
-
-
- fun f1 x = if null x then 0 else 1 + hd x;
val f1 = fn : int list -> int
- f1 [1,2,3];
val it = 2 : int
- f1 [];
val it = 0 : int
-
-
-
- fun f1 [] = 0
=   | f1 (x :: xs) = 1 + x;
val f1 = fn : int list -> int
- f1 [];
val it = 0 : int
- f1 [1,2,3];
val it = 2 : int
-
-
- fun f1 x = if null x then
=               0
=             else
=               1 + hd x;
val f1 = fn : int list -> int
-
-
- fun f2 x = hd x + hd (tl x);
val f2 = fn : int list -> int
- f2 [1,3];
val it = 4 : int
- f2 [1,2,3,4];
val it = 3 : int
- f2 [5,2,3,4];
val it = 7 : int
- f2 [5];

uncaught exception Empty
  raised at: smlnj/init/pervasive.sml:193.19-193.24
-
- f2 [];

uncaught exception Empty
  raised at: smlnj/init/pervasive.sml:193.19-193.24
-
-
- fun f2 (x :: y :: ys) = x + y;
stdIn:44.5-44.30 Warning: match nonexhaustive
          x :: y :: ys => ...

val f2 = fn : int list -> int
-
- fun f2 x = if null x then 0 else if null (tl x) then hd x else hd x + hd (tl x);
val f2 = fn : int list -> int
-
-
- f2 [];
val it = 0 : int
- f2 [3];
val it = 3 : int
- f2 [3, 4];
val it = 7 : int
-
-
-