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.\" ========================================================================
.\"
.IX Title "Psh::Strategy 3"
.TH Psh::Strategy 3 "2003-01-02" "perl v5.8.0" "User Contributed Perl Documentation"
.SH "NAME"
Psh::Strategy \- a Perl Shell Evaluation Strategy (base class)
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Psh::Strategy;
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Psh::Strategy offers a procedural strategy list interface and a
base class for developing strategies.
.SH "PROCEDURAL STRATEGY LIST"
.IX Header "PROCEDURAL STRATEGY LIST"
.Vb 1
\&  Psh::Strategy::list()
.Ve
.PP
Returns a list of active Psh::Strategy objects.
.PP
.Vb 1
\&  my $obj= Psh::Strategy::get('name')
.Ve
.PP
Loads and initializes a certain Psh::Strategy object
.PP
.Vb 1
\&  Psh::Strategy::add($obj [, $suggest_position])
.Ve
.PP
Adds a strategy object to the list of active strategies
.PP
.Vb 1
\&  Psh::Strategy::remove($name)
.Ve
.PP
Removes a strategy
.PP
.Vb 1
\&  @list= Psh::Strategy::available_list()
.Ve
.PP
Lists available strategies
.PP
.Vb 1
\&  my $pos= find($name)
.Ve
.PP
Finds the position of the named strategy
.PP
.Vb 1
\&  my $flag= active($name)
.Ve
.PP
Returns true if the named strategy is currently active
.SH "DEVELOPING STRATEGIES"
.IX Header "DEVELOPING STRATEGIES"
You have to inherit from Psh::Strategy and you \s-1MUST\s0 at least
override the functions \f(CW\*(C`consumes\*(C'\fR, \f(CW\*(C`applies\*(C'\fR, \f(CW\*(C`execute\*(C'\fR.
You \s-1CAN\s0 also override the function \f(CW\*(C`runs_before\*(C'\fR
.IP "\(bu consumes" 4
.IX Item "consumes"
Returns either \s-1CONSUME_LINE\s0, \s-1CONSUME_WORDS\s0, \s-1CONSUME_TOKENS\s0.
\&\s-1CONSUME_LINE\s0 means you want to receive the whole input line
unparsed. \s-1CONSUME_WORDS\s0 means you want to receive the whole
input line tokenized (currenty unimplemented). \s-1CONSUME_TOKENS\s0
means that you want to receive a sub-part of the line, tokenized
(this is probably what you want)
.IP "\(bu applies" 4
.IX Item "applies"
Returns undef if the strategy does not want to handle the input.
Returns a human-readable description if it wants to handle the input.
.Sp
If you specified \s-1CONSUME_LINE\s0, this method will be called as
  \f(CW$obj\fR\->applies(\e$inputline);
.Sp
If you specified \s-1CONSUME_TOKENS\s0, this method will be called as
  \f(CW$obj\fR\->applies(\e$inputline,\e@tokens,$piped_flag)
.IP "\(bu execute" 4
.IX Item "execute"
Will be called as
  \f(CW$obj\fR\->execute(\e$inputline,\e@tokens,$how,$piped_flag)
.Sp
\&\f(CW$how\fR is what the call to applies returned. If \f(CW@tokens\fR is
not applicable an empty array will be supplied.
.Sp
Your execute function should return an array of the form:
.Sp
.Vb 1
\&  ($evalcode, \e@words, $forcefork, @return_val)
.Ve
.Sp
If \f(CW$evalcode\fR, <@words> and <$forcefork> are undef, execution is finished
after this call and \f(CW@return_val\fR will be used as return value.
.Sp
But \f(CW$evalcode\fR can also be a Perl sub \- in which case it is evaluated
later on, or a string \- in which case it's a filename of a program to
execute. \f(CW@words\fR will then be used as arguments for the program.
.Sp
\&\f(CW$forcefork\fR may be used to force a \f(CW\*(C`fork()\*(C'\fR call even for the perl
subs.
.IP "\(bu runs_before" 4
.IX Item "runs_before"
Returns a list of names of other strategies. It is guaranteed that
the evaluation strategy will be tried before those other named strategies
are tried.