get_var_info(?Var, ?InfoName, -Value)

Var

Prolog Term, usually a variable.

InfoName

Atom or variable.

Value

Atom or variable.

Description

The possible values for InfoName are type or name.

If InfoName unifies with name, the predicate will succeed if the source name of the free variable Var is available and unifies with Value.

If InfoName unifies with type, the predicate will succeed if Value unifies with the type of the variable Var.

The possible types are:

    meta      an attributed variable (metaterm)
    free      a free variable

Modes and Determinism

• get_var_info(?, +, -) is semidet
• get_var_info(?, -, -) is semidet

Fail Conditions

Exceptions

(5) type error

InfoName or Value is neither an atom nor a variable.

(6) out of range

InfoName is not an information name.

Examples

Success:
      ?- suspend:(Var1 > Var2), get_var_info(Var1, Info, Value).
      Var2 = Var2
      Var1 = Var1
      Info = name
      Value = 'Var1'
      Delayed goals:
       Var1 > Var2     More? (;)

      Var2 = Var2
      Var1 = Var1
      Info = type
      Value = meta

      Delayed goals:
       Var1 > Var2
      yes.

      ?- get_var_info(Var1, type, Type).
      Var1 = Var1
      Type = free
      yes.

      ?- set_flag(variable_names,off).
      yes.

      ?- get_var_info(Var1, name, Name).
      no (more) solution.

Fail:
      get_var_info(atom, name, Name).
      set_flag(variable_names, off),
          get_var_info(X, name, Name).

Error:
      get_var_info(X, not_an_info, Y).    (Error 6)
      get_var_info(X, type, 123).         (Error 5)

See Also