# SQL::Statement::Function - phpMan

## NAME
    [SQL::Statement::Function] - abstract base class for all function
    executing terms

## SYNOPSIS
      # this class does not have a common constructor, because all derived classes
      # have their special requirements

## DESCRIPTION
    [SQL::Statement::Function] is an abstract base class providing the
    interface for all function executing terms.

## INHERITANCE
      [SQL::Statement::Function]
      ISA [SQL::Statement::Term]

## METHODS
  DESTROY
    Destroys the term and undefines the weak reference to the owner as well
    as the reference to the parameter list.

## NAME
    [SQL::Statement::Function::UserFunc] - implements executing a perl
    subroutine

## SYNOPSIS
      # create an user function term with an [SQL::Statement] object as owner,
      # specifying the function name, the subroutine name (full qualified)
      # and the parameters to the subroutine
      my $term = [SQL::Statement::Function::UserFunc]->new( $owner, $name, $sub, \@params );
      # access the result of that operation
      $term->value( $eval );

## DESCRIPTION
    [SQL::Statement::Function::UserFunc] implements a term which returns the
    result of the specified subroutine.

## INHERITANCE
      [SQL::Statement::Function]
      ISA [SQL::Statement::Term]

## METHODS
  new
    Instantiates a new "[SQL::Statement::Function::UserFunc]" instance.

  value
    Invokes the given subroutine with the values of the params and return
    it's result:

        my @params = map { $_->value($eval); } @{ $self->{PARAMS} };
        return $subpkg->$subname( $self->{OWNER}, @params );

## NAME
    [SQL::Statement::Function::NumericEval] - implements numeric evaluation of
    a term

## SYNOPSIS
      # create an user function term with an [SQL::Statement] object as owner,
      # specifying the expression to evaluate and the parameters to the subroutine
      my $term = [SQL::Statement::NumericEval]->new( $owner, $expr, \@params );
      # access the result of that operation
      $term->value( $eval );

## DESCRIPTION
    [SQL::Statement::Function::NumericEval] implements the numeric evaluation
    of a term. All parameters are expected to be numeric.

## INHERITANCE
      [SQL::Statement::Function::NumericEval]
      ISA [SQL::Statement::Function]
        ISA [SQL::Statement::Term]

## METHODS
  new
    Instantiates a new "[SQL::Statement::Function::NumericEval]" instance.
    Takes *$owner*, *$expr* and *\@params* as arguments (in specified
    order).

  value
    Returns the result of the evaluated expression.

## NAME
    [SQL::Statement::Function::Trim] - implements the built-in trim function
    support

## SYNOPSIS
      # create an trim function term with an [SQL::Statement] object as owner,
      # specifying the spec, char and the parameters to the subroutine
      my $term = [SQL::Statement::Trim]->new( $owner, $spec, $char, \@params );
      # access the result of that operation
      $term->value( $eval );

## DESCRIPTION
    [SQL::Statement::Function::Trim] implements string trimming.

## INHERITANCE
      [SQL::Statement::Function::Trim]
      ISA [SQL::Statement::Function]
        ISA [SQL::Statement::Term]

## METHODS
  new
    Instantiates a new "[SQL::Statement::Function::Trim]" instance. Takes
    *$owner*, *$spec*, *$char* and *\@params* as arguments (in specified
    order).

    Meaning of the parameters:

    *$spec*
        Can be on of 'LEADING', 'TRAILING' 'BOTH'. Trims the leading chars,
        trailing chars or at both ends, respectively.

        Defaults to 'BOTH'.

    *$char*
        The character to trim - defaults to ' '

    *\@params*
        Expected to be an array with exact 1 element (more are not
        evaluated).

  value
    Returns the trimmed value of first parameter argument.

## NAME
    [SQL::Statement::Function::SubString] - implements the built-in sub-string
    function support

## SYNOPSIS
      # create an substr function term with an [SQL::Statement] object as owner,
      # specifying the start and length of the sub string to extract from the
      # first element of \@params
      my $term = [SQL::Statement::SubString]->new( $owner, $start, $length, \@params );
      # access the result of that operation
      $term->value( $eval );

## DESCRIPTION
    [SQL::Statement::Function::SubString] implements a sub-string extraction
    term.

## INHERITANCE
      [SQL::Statement::Function::SubString]
      ISA [SQL::Statement::Function]
        ISA [SQL::Statement::Term]

## METHODS
  new
    Instantiates a new "[SQL::Statement::Function::SubString]" instance. Takes
    *$owner*, *$start*, *$length* and *\@params* as arguments (in specified
    order).

    Meaning of the parameters:

    *$start*
        Specifies the start position to extract the sub-string. This is
        expected to be a [SQL::Statement::Term] instance. The first character
        in a string has the position 1.

    *$length*
        Specifies the length of the extracted sub-string. This is expected
        to be a [SQL::Statement::Term] instance.

        If omitted, everything to the end of the string is returned.

    *\@params*
        Expected to be an array with exact 1 element (more are not
        evaluated).

  value
    Returns the extracted sub-string value from first parameter argument.

## NAME
    [SQL::Statement::Function::StrConcat] - implements the built-in string
    concatenation

## SYNOPSIS
      # create an substr function term with an [SQL::Statement] object as owner
      # and \@params to concatenate
      my $term = [SQL::Statement::StrConcat]->new( $owner, \@params );
      # access the result of that operation
      $term->value( $eval );

## DESCRIPTION
    [SQL::Statement::Function::StrConcat] implements a string concatenation
    term.

## INHERITANCE
      [SQL::Statement::Function::StrConcat]
      ISA [SQL::Statement::Function]
        ISA [SQL::Statement::Term]

## METHODS
  new
    Instantiates a new "[SQL::Statement::Function::StrConcat]" instance.

  value
    Returns the concatenated string composed of the parameter values.

## AUTHOR AND COPYRIGHT
    Copyright (c) 2009-2020 by Jens Rehsack: rehsackATcpan.org

    All rights reserved.

    You may distribute this module under the terms of either the GNU General
    Public License or the Artistic License, as specified in the Perl README
    file.