sl@0: /*============================================================================= sl@0: Adaptable closures sl@0: sl@0: Phoenix V0.9 sl@0: Copyright (c) 2001-2002 Joel de Guzman sl@0: sl@0: Distributed under the Boost Software License, Version 1.0. (See sl@0: accompanying file LICENSE_1_0.txt or copy at sl@0: http://www.boost.org/LICENSE_1_0.txt) sl@0: sl@0: URL: http://spirit.sourceforge.net/ sl@0: sl@0: ==============================================================================*/ sl@0: #ifndef PHOENIX_CLOSURES_HPP sl@0: #define PHOENIX_CLOSURES_HPP sl@0: sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: #include "boost/lambda/core.hpp" sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: namespace boost { sl@0: namespace lambda { sl@0: sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: // sl@0: // Adaptable closures sl@0: // sl@0: // The framework will not be complete without some form of closures sl@0: // support. Closures encapsulate a stack frame where local sl@0: // variables are created upon entering a function and destructed sl@0: // upon exiting. Closures provide an environment for local sl@0: // variables to reside. Closures can hold heterogeneous types. sl@0: // sl@0: // Phoenix closures are true hardware stack based closures. At the sl@0: // very least, closures enable true reentrancy in lambda functions. sl@0: // A closure provides access to a function stack frame where local sl@0: // variables reside. Modeled after Pascal nested stack frames, sl@0: // closures can be nested just like nested functions where code in sl@0: // inner closures may access local variables from in-scope outer sl@0: // closures (accessing inner scopes from outer scopes is an error sl@0: // and will cause a run-time assertion failure). sl@0: // sl@0: // There are three (3) interacting classes: sl@0: // sl@0: // 1) closure: sl@0: // sl@0: // At the point of declaration, a closure does not yet create a sl@0: // stack frame nor instantiate any variables. A closure declaration sl@0: // declares the types and names[note] of the local variables. The sl@0: // closure class is meant to be subclassed. It is the sl@0: // responsibility of a closure subclass to supply the names for sl@0: // each of the local variable in the closure. Example: sl@0: // sl@0: // struct my_closure : closure { sl@0: // sl@0: // member1 num; // names the 1st (int) local variable sl@0: // member2 message; // names the 2nd (string) local variable sl@0: // member3 real; // names the 3rd (double) local variable sl@0: // }; sl@0: // sl@0: // my_closure clos; sl@0: // sl@0: // Now that we have a closure 'clos', its local variables can be sl@0: // accessed lazily using the dot notation. Each qualified local sl@0: // variable can be used just like any primitive actor (see sl@0: // primitives.hpp). Examples: sl@0: // sl@0: // clos.num = 30 sl@0: // clos.message = arg1 sl@0: // clos.real = clos.num * 1e6 sl@0: // sl@0: // The examples above are lazily evaluated. As usual, these sl@0: // expressions return composite actors that will be evaluated sl@0: // through a second function call invocation (see operators.hpp). sl@0: // Each of the members (clos.xxx) is an actor. As such, applying sl@0: // the operator() will reveal its identity: sl@0: // sl@0: // clos.num() // will return the current value of clos.num sl@0: // sl@0: // *** [note] Acknowledgement: Juan Carlos Arevalo-Baeza (JCAB) sl@0: // introduced and initilally implemented the closure member names sl@0: // that uses the dot notation. sl@0: // sl@0: // 2) closure_member sl@0: // sl@0: // The named local variables of closure 'clos' above are actually sl@0: // closure members. The closure_member class is an actor and sl@0: // conforms to its conceptual interface. member1..memberN are sl@0: // predefined typedefs that correspond to each of the listed types sl@0: // in the closure template parameters. sl@0: // sl@0: // 3) closure_frame sl@0: // sl@0: // When a closure member is finally evaluated, it should refer to sl@0: // an actual instance of the variable in the hardware stack. sl@0: // Without doing so, the process is not complete and the evaluated sl@0: // member will result to an assertion failure. Remember that the sl@0: // closure is just a declaration. The local variables that a sl@0: // closure refers to must still be instantiated. sl@0: // sl@0: // The closure_frame class does the actual instantiation of the sl@0: // local variables and links these variables with the closure and sl@0: // all its members. There can be multiple instances of sl@0: // closure_frames typically situated in the stack inside a sl@0: // function. Each closure_frame instance initiates a stack frame sl@0: // with a new set of closure local variables. Example: sl@0: // sl@0: // void foo() sl@0: // { sl@0: // closure_frame frame(clos); sl@0: // /* do something */ sl@0: // } sl@0: // sl@0: // where 'clos' is an instance of our closure 'my_closure' above. sl@0: // Take note that the usage above precludes locally declared sl@0: // classes. If my_closure is a locally declared type, we can still sl@0: // use its self_type as a paramater to closure_frame: sl@0: // sl@0: // closure_frame frame(clos); sl@0: // sl@0: // Upon instantiation, the closure_frame links the local variables sl@0: // to the closure. The previous link to another closure_frame sl@0: // instance created before is saved. Upon destruction, the sl@0: // closure_frame unlinks itself from the closure and relinks the sl@0: // preceding closure_frame prior to this instance. sl@0: // sl@0: // The local variables in the closure 'clos' above is default sl@0: // constructed in the stack inside function 'foo'. Once 'foo' is sl@0: // exited, all of these local variables are destructed. In some sl@0: // cases, default construction is not desirable and we need to sl@0: // initialize the local closure variables with some values. This sl@0: // can be done by passing in the initializers in a compatible sl@0: // tuple. A compatible tuple is one with the same number of sl@0: // elements as the destination and where each element from the sl@0: // destination can be constructed from each corresponding element sl@0: // in the source. Example: sl@0: // sl@0: // tuple init(123, "Hello", 1000); sl@0: // closure_frame frame(clos, init); sl@0: // sl@0: // Here now, our closure_frame's variables are initialized with sl@0: // int: 123, char const*: "Hello" and int: 1000. sl@0: // sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: sl@0: sl@0: sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: // sl@0: // closure_frame class sl@0: // sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: template sl@0: class closure_frame : public ClosureT::tuple_t { sl@0: sl@0: public: sl@0: sl@0: closure_frame(ClosureT& clos) sl@0: : ClosureT::tuple_t(), save(clos.frame), frame(clos.frame) sl@0: { clos.frame = this; } sl@0: sl@0: template sl@0: closure_frame(ClosureT& clos, TupleT const& init) sl@0: : ClosureT::tuple_t(init), save(clos.frame), frame(clos.frame) sl@0: { clos.frame = this; } sl@0: sl@0: ~closure_frame() sl@0: { frame = save; } sl@0: sl@0: private: sl@0: sl@0: closure_frame(closure_frame const&); // no copy sl@0: closure_frame& operator=(closure_frame const&); // no assign sl@0: sl@0: closure_frame* save; sl@0: closure_frame*& frame; sl@0: }; sl@0: sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: // sl@0: // closure_member class sl@0: // sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: template sl@0: class closure_member { sl@0: sl@0: public: sl@0: sl@0: typedef typename ClosureT::tuple_t tuple_t; sl@0: sl@0: closure_member() sl@0: : frame(ClosureT::closure_frame_ref()) {} sl@0: sl@0: template sl@0: struct sig { sl@0: sl@0: typedef typename detail::tuple_element_as_reference< sl@0: N, typename ClosureT::tuple_t sl@0: >::type type; sl@0: }; sl@0: sl@0: template sl@0: // typename detail::tuple_element_as_reference sl@0: // ::type sl@0: Ret sl@0: call(A&, B&, C&) const sl@0: { sl@0: assert(frame); sl@0: return boost::tuples::get(*frame); sl@0: } sl@0: sl@0: sl@0: private: sl@0: sl@0: typename ClosureT::closure_frame_t*& frame; sl@0: }; sl@0: sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: // sl@0: // closure class sl@0: // sl@0: /////////////////////////////////////////////////////////////////////////////// sl@0: template < sl@0: typename T0 = null_type, sl@0: typename T1 = null_type, sl@0: typename T2 = null_type, sl@0: typename T3 = null_type, sl@0: typename T4 = null_type sl@0: > sl@0: class closure { sl@0: sl@0: public: sl@0: sl@0: typedef tuple tuple_t; sl@0: typedef closure self_t; sl@0: typedef closure_frame closure_frame_t; sl@0: sl@0: closure() sl@0: : frame(0) { closure_frame_ref(&frame); } sl@0: closure_frame_t& context() { assert(frame); return frame; } sl@0: closure_frame_t const& context() const { assert(frame); return frame; } sl@0: sl@0: typedef lambda_functor > member1; sl@0: typedef lambda_functor > member2; sl@0: typedef lambda_functor > member3; sl@0: typedef lambda_functor > member4; sl@0: typedef lambda_functor > member5; sl@0: sl@0: private: sl@0: sl@0: closure(closure const&); // no copy sl@0: closure& operator=(closure const&); // no assign sl@0: sl@0: template sl@0: friend struct closure_member; sl@0: sl@0: template sl@0: friend class closure_frame; sl@0: sl@0: static closure_frame_t*& sl@0: closure_frame_ref(closure_frame_t** frame_ = 0) sl@0: { sl@0: static closure_frame_t** frame = 0; sl@0: if (frame_ != 0) sl@0: frame = frame_; sl@0: return *frame; sl@0: } sl@0: sl@0: closure_frame_t* frame; sl@0: }; sl@0: sl@0: }} sl@0: // namespace sl@0: sl@0: #endif