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/*
FALCON - The Falcon Programming Language.
FILE: functional_ext.cpp
Functional programming support
-------------------------------------------------------------------
Author: Giancarlo Niccolai
Begin: Thu, 14 Aug 2008 02:10:57 +0200
-------------------------------------------------------------------
(C) Copyright 2008: the FALCON developers (see list in AUTHORS file)
See LICENSE file for licensing details.
*/
#include "core_module.h"
/*#
@beginmodule core
*/
namespace Falcon {
namespace core {
/*#
@funset oob_support Out of band items support
@brief Handle out of band items.
Out-of-band items are normal items which can be tested for the out-of-band quality
through the @a isoob function to perform special tasks. Some core and RTL functions can
check for the item being out-of-band to take special decisions about the item, or to
modify their behavior. For example, the @a map function drops the item (acting like @a filter ),
if it is out-of-band.
This feature is available also to scripts; functions accepting any kind of items from
callbacks they are using to generate data may wish to receive special instructions
through out of band data. In the next example, a data producer returns a set of items
one at a time, and notifies the caller to switch to another producer via an out-of-band
notification.
@code
function firstSeries()
static: vals = [1, 2, 3, 4 ]
if vals: return arrayHead( vals )
// notify the next function
return oob( secondSeries )
end
function secondSeries()
static: vals = [ "a", nil, "b", 4 ]
if vals: return arrayHead( vals )
// notify we're done with an nil OOB
return oob()
end
function consumer( producer )
loop item = producer()
if isoob( item )
// An OOB means we have something special. If it's nil, we're done...
if item == nil: return
// else it's the notification of a new producer
producer = item
else
// if it's not an OOB, then we must process it
> "Received item: ", item
end
end
end
consumer( firstSeries )
@endcode
Marking an item as out-of-band allows the creation of @i monads in functional evaluations.
More automatism will be introduced in future, but scripters can have monads by assigning the
oob status to complex objects and perform out-of-band processing on them.
*/
/*#
@function oob
@brief Generates an out-of-band item.
@inset oob_support
@optparam item The item to be declared out of band.
@return An oob version of the item, or an oob @b nil if no item is given.
This function returns an out-of-band nil item, or if a parameter is given,
an out-of-band version of that item.
*/
FALCON_FUNC core_oob( ::Falcon::VMachine *vm )
{
Item *obbed = vm->param(0);
if ( ! obbed )
{
vm->regA().setNil();
}
else {
vm->regA() = *obbed;
}
vm->regA().setOob();
}
/*#
@function deoob
@brief Turns an out-of-band item in a normal item.
@inset oob_support
@param item The out of band item to be turned into a normal item.
@return An the non-out-of-band version version of the item.
The function returns a flat copy of the item without the out-of-band status set.
If the item was initially not OOB, then deoob() does nothing.
See @a oob for a deeper explanation of OOB items.
*/
FALCON_FUNC core_deoob( ::Falcon::VMachine *vm )
{
Item *obbed = vm->param(0);
if ( ! obbed )
{
throw new ParamError( ErrorParam( e_inv_params, __LINE__ )
.origin( e_orig_runtime )
.extra( "X" ) );
return;
}
vm->regA() = *obbed;
vm->regA().resetOob();
}
/*#
@function isoob
@brief Checks for the out-of-band status of an item.
@inset oob_support
@param item The item to be checked.
@return True if the item is out of band, false otherwise.
This function can be used to check if a certain item is an out of band item.
*/
FALCON_FUNC core_isoob( ::Falcon::VMachine *vm )
{
Item *obbed = vm->param(0);
if ( ! obbed )
{
throw new ParamError( ErrorParam( e_inv_params, __LINE__ )
.origin( e_orig_runtime )
.extra( "X" ) );
return;
}
vm->regA().setBoolean( obbed->isOob() );
}
}
}
/* end of oob_ext.cpp */
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