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# help(+PredSpec)

Prints help information on the specified predicate in PredSpec on the current output.

PredSpec
  Predicate/Library specification in form Name/Arity or Module:Name/Arity, lib(Name), or an atom Name

## Description

Prints help information about the specified predicates to the current output. The information displayed is a text version of the reference manual. If only Name is specified, the system looks for all predicates that have this atom in their name. If there are more than one predicate matching, a short description for each one is printed, rather than the whole page. For instance, help var prints the short description of get_var_info/3, nonvar/1, readvar/3, var/1 and variant/2, whereas help dv prints the whole reference manual page for readvar/3.

Help information is available for both built-ins (those predicates defined in eclipse_language) and library predicates. If a particular predicate is available in more than one library, the user can specify Module:Name/Arity for PredSpec where Module is the name of the library to select a specific predicate description. If a predicate is available both as a built-in and library predicate(s), then the built-in will be printed in full, while short descriptions are given for the library predicates.

In addition, if information on library is available, help lib(LibraryName) can be used to obtain this information.

### Modes and Determinism

- help(+) is semidet

### Fail Conditions

Fails if no help is available for PredSpec

## Examples

    Success:
          help(nl/0).         % Displays reference page on nl/0

          help(write/X).      % Displays short description of
      % write/1 and write/2

          help(fd:(::)/2).    % Displays the reference page for fd's ::/2.

          help((=:=)/2).      % Displays reference page for the built-in =:=/2,
      % and short description of the other instances of =:=/2.

          help(lib(eplex)).   % Displays the reference page for the library eplex.
          help(X).            % Displays short description of
      % all built-ins

    Fail:
          help(nobip/1).

## See Also

current_built_in / 1