getval(+ElemSpec, ?Value)

+ElemSpec

Atom or ground compound term with non negative integer arguments.

?Value

Prolog term.

Description

If ElemSpec is a compound term, it must specify an element of a visible non-logical array, all its arguments must be non negative integers smaller than the bounds specified with array/1/2 or variable/1. The copied value of the array element is unified with Value.

If Element is the name of a reference, Value is unified with the actual term the reference refers to (no copying involved).

Fail Conditions

Resatisfiable

Exceptions

(4) instantiation fault

ElemSpec is not ground.

(5) type error

ElemSpec is neither an atom nor a structure whose arguments are integers.

(6) out of range

An array index in ElemSpec is out of bounds

(41) array or global variable does not exist

ElemSpec does not designate an existing array, variable or reference.

Examples

Success:
      local(array(a(4), float)),
          setval(a(2), 2.0),
          getval(a(2), 2.0).
      setval(i, "2"),
          getval(i, V)).   (gives V = "2").

Failure:
      local(array(a(2))),
          setval(a(1), 8.6),
          getval(a(1), 10.0).
      setval(i, 3),
          getval(i, 0)).

Error:
      getval(X, 1).                   (Error 4).
      getval(a(X), 1).                (Error 4).
      getval("a", V).                 (Error 5).
      getval(a(2.0), V).              (Error 5).
      getval(a(-1), V).               (Error 6).
      getval(no_array(0), X).         (Error 41).
      getval(no_var, X).              (Error 41).

See Also