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incval(++ElemSpec)

Increments the contents of the visible non-logical variable or array element ElemSpec by one.
ElemSpec
Atom or ground compound term with non negative integer arguments.

Description

Increments the value of the element ElemSpec that must be of type integer.

If ElemSpec is an atom, it must specify a non-logical variable visible from the caller module.

If ElemSpec is a compound term, it must specify a visible array element. all its arguments must be non negative integers smaller than the bounds specified with array/1/2 or variable/1.

In a multithreaded setting, this operation can be considered atomic.

Modes and Determinism

Modules

This predicate is sensitive to its module context (tool predicate, see @/2).

Exceptions

(4) instantiation fault
ElemSpec is not instantiated.
(5) type error
ElemSpec is a structure whose arguments are not all integers.
(5) type error
ElemSpec is neither an atom nor a ground structure.
(5) type error
The value or type of ElemSpec is not integer.
(6) out of range
Array index in ElemSpec is out of range.
(41) array or global variable does not exist
ElemSpec does not designate an existing array or variable.

Examples

Success:
      [eclipse]: local(array(a(4), prolog)),
              setval(a(1), -2),
              incval(a(1)),
              getval(a(1), X).
      X = -1
      yes.

      [eclipse]: local(array(g(4), integer)),
              incval(g(1)),
              getval(g(1), X).
      X = 1
      yes.

      [eclipse]: setval(count, 0),
              repeat,
              writeln(hello),
              incval(count),
              getval(count, X),
              X >= 3, !.
      hello
      hello
      hello
      X = 3
      yes.

Error:

      incval(X).                            (Error 4).
      incval(a(2.0)).                       (Error 5).
      setval(a, 2.0), incval(a).            (Error 5).
      local(array(a(2), float)),
          incval(a(1)).                     (Error 5).
      local(array(a(10), integer)),
          incval(a(-2)).                    (Error 6).
      incval(no_array(0)).                  (Error 41).
      incval(no_var).                       (Error 41).



See Also

decval / 1, array / 1, array / 2, variable / 1, getval / 2, setval / 2