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# autoload_tool(+Library, ++ListOfPredSpecList)

Declares the predicates in ListOfPredSpec to be autoloading tools from the module (file) Library.pl.

Library
  Atom.
ListOfPredSpecList
  of expressions of the form Atom/Integer.

### This built-in predicate is obsolete!

## Description

Declares the predicates in the list ListOfPredSpec as tools defined in the file Library. If any of the specified tools is called, the system looks in the library_path directories for the file Library.pl, compiles it using lib/1 and re-calls the tool. The file is supposed to contain a module_interface/1 or begin_module/1 directive at its beginning but it can be omitted and then Library is used as the module name.

The library file Library.pl must contain a tool/2 call for each of the specified predicates.

Predicates declared as autoloaded are always defined as global but note that the module directive in a file erase the module completely so that the autoloaded procedure (and its visibility) are removed completely before being recompiled. This means that the global declaration must be present in the file.

### Modes and Determinism

- autoload_tool(+, ++) is det

### Exceptions

(4) instantiation fault
  Library or ListOfPredSpec is not instantiated.
(5) type error
  Library is instantiated, but not to an atom.
(5) type error
  ListOfPredSpec is instantiated, but not to a list of expressions of the form Atom/Integer.
(62) inconsistent procedure redefinition
  a call to PredSpec has already been compiled before the tool declaration (``inconsistent procedure redefinition'').
(173) library not found
  Library file Library.pl not found. (when calling an autoloaded predicate)

## Examples

    Success:
         [eclipse]: get_flag(library_path, Path),
                 get_flag(cwd, Cwd),
                 set_flag(library_path, [Cwd | Path]).
         Cwd = "/home/user/"
         Path = ["/usr/local/ECLIPSE/lib"]
         yes.
         [eclipse]: open("my_lib.pl", write, s),
                 write(s, ":- module(my_lib).\n"),
                 write(s, ":- global p/0.\n"),
                 write(s, ":- tool(p/0, writeln/1)."),
                 close(s).
         yes.
         [eclipse]: autoload_tool(my_lib, [p/0]).
         yes.
         [eclipse]: p.       % when p/0 is called, the library is
                           % compiled first, ie. autoloaded.
         loading the library /home/user/my_lib.pl
         eclipse
         yes.
         [eclipse]: p.       % p/0 is not an autoloaded pred anymore
         eclipse
         yes.

    Error:
         autoload_tool(Lib, [p/0]).            (Error 4).
         autoload_tool(a_lib, L).              (Error 4).
         autoload_tool("a_lib", [p/0]).        (Error 5).
         autoload_tool(a_lib, [1]).            (Error 5).
         autoload_tool(a_lib, p/0).            (Error 5).

         [eclipse]: [user].
          p :- t. % call compiled before tool declaration
          user compiled 32 bytes in 0.00 seconds
         yes.
         [eclipse]: autoload_tool(a_lib, [t/0]). (Error 62).

         autoload_tool(not_a_file, [p/0]).     (Error 173).

## See Also

ensure_loaded / 1, autoload / 2, lib / 1, lib / 2, tool / 1