Type testing

6.1 | Type testing

6.1.1 | `var/1`, `nonvar/1`, `atom/1`, `integer/1`, `float/1`, `number/1`, `atomic/1`, `compound/1`, `callable/1`, `list/1`, `partial_list/1`, `list_or_partial_list/1`

Templates

  `var(?term)
  nonvar(?term)
  atom(?term)
  integer(?term)
  float(?term)
  number(?term)
  atomic(?term)
  compound(?term)
  callable(?term)
  list(?term)
  partial_list(?term)
  list_or_partial_list(?term)`

Description
`var(Term)` succeeds if `Term` is currently uninstantiated (which therefore has not been bound to anything, except possibly another uninstantiated variable).
`nonvar(Term)` succeeds if `Term` is currently instantiated (opposite of `var/1`).
`atom(Term)` succeeds if `Term` is currently instantiated to an atom.
`integer(Term)` succeeds if `Term` is currently instantiated to an integer.
`float(Term)` succeeds if `Term` is currently instantiated to a floating point number.
`number(Term)` succeeds if `Term` is currently instantiated to an integer or a floating point number.
`atomic(Term)` succeeds if `Term` is currently instantiated to an atom, an integer or a floating point number.
`compound(Term)` succeeds if `Term` is currently instantiated to a compound term, i.e. a term of arity > 0 (a list or a structure).
`callable(Term)` succeeds if `Term` is currently instantiated to a callable term, i.e. an atom or a compound term.
`list(Term)` succeeds if `Term` is currently instantiated to a list, i.e. the atom `[]` (empty list) or a term with principal functor `'.'/2` and with second argument (the tail) a list.
`partial_list(Term)` succeeds if `Term` is currently instantiated to a partial list, i.e. a variable or a term whose the main functor is `'.'/2` and the second argument (the tail) is a partial list.
`list_or_partial_list(Term)` succeeds if `Term` is currently instantiated to a list or a partial list.
Errors
None.
Portability
`var/1`, `nonvar/1`, `atom/1`, `integer/1`, `float/1`, `number/1`, `atomic/1`, `compound/1` and `callable/1` are ISO predicates.
`list/1`, `partial_list/1` and `list_or_partial_list/1` are GNU Prolog predicates.

Copyright (C) 1999,2000 Daniel Diaz
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