PC World Komputer 1999 mARCH/PCWK3A99.iso/Linux/DDD331/DDD-3_1_.000/DDD-3_1_/ddd-3.1.1/ddd/LetNode.h

C/C++ Source or Header | 1998-11-23 | 5KB | 185 lines

// $Id: LetNode.h,v 1.13 1998/11/23 17:43:27 zeller Exp $
// LET..IN construct in VSL

// Copyright (C) 1995 Technische Universitaet Braunschweig, Germany.
// Written by Andreas Zeller <[e-mail]>.
//
// This file is part of DDD.
//
// DDD is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// DDD is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// See the GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public
// License along with DDD -- see the file COPYING.
// If not, write to the Free Software Foundation, Inc.,
// 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
//
// DDD is the data display debugger.
// For details, see the DDD World-Wide-Web page,
// `http://www.cs.tu-bs.de/softech/ddd/',
// or send a mail to the DDD developers <[e-mail]>.

#ifndef _DDD_LetNode_h
#define _DDD_LetNode_h

#ifdef __GNUG__
#pragma interface
#endif


// A LetNode implements a LET..IN construct.

// A LetNode contains a list of length 2.
// Upon evaluation, the first list element is matched against a pattern.
// The variables found this way are used in evaluating the second element.


#include "assert.h"
#include <iostream.h>

#include "VSLNode.h"
#include "ListNode.h"
#include "CallNode.h"
#include "TrueNode.h"



// LetNode

class LetNode: public CallNode {
public:
    DECLARE_TYPE_INFO

private:
    VSLNode *_node_pattern;    // Pattern
    Box *_box_pattern;        // Compiled pattern

    unsigned _nargs;        // Number of args
    bool _straight;        // Flag: use argument list `as is'?

    bool being_compiled;    // Protect against recursive patterns

    ListNode *_args() const      { return (ListNode *)arg(); }
    ListNode *_body() const      { return (ListNode *)(_args()->tail()); }

    ListBox *arglist(const Box *arg) const;       // Build arg list (Box)
    VSLNode **nodelist(const VSLNode *arg) const; // same, with nodes

    bool domatch(const Box *arg) const;        // Match against Box
    bool domatch(const VSLNode *arg) const;    // Match against Ausdruck

protected:
    void dump(ostream& s) const;
    void _dumpTree(ostream& s) const;

    LetNode(const LetNode& node):
    CallNode(node),
    _node_pattern(node._node_pattern->dup()),
    _box_pattern(0),
    _nargs(node._nargs),
    _straight(node._straight),
    being_compiled(false)
    {
    if (node._box_pattern)
        _box_pattern = node._box_pattern->link();
    }

    // Never called
    char *func_name() const       { assert(0); return "let"; }
    const Box *call(Box *) const  { assert(0); return 0; }

private:
    LetNode& operator = (const LetNode&) { assert(0); return *this; }

public:
    // Constructor
    LetNode(VSLNode *p, VSLNode *a, VSLNode *b, char *type = "LetNode"):
    CallNode(new FixListNode(a, b), type),
    _node_pattern(p),
    _box_pattern(0),
    _nargs(p->nargs()),
    _straight(p->isStraight()),
    being_compiled(false)
    {}

    // Destructor
    ~LetNode()
    {
    if (_node_pattern) delete _node_pattern;
    if (_box_pattern) _box_pattern->unlink();
    }

    // Resources
    VSLNode *&node_pattern()    { return _node_pattern; }
    Box *&box_pattern()         { return _box_pattern; }
    VSLNode *&args()            { return _args()->head(); }
    VSLNode *&body()            { return _body()->head(); }

    const VSLNode *node_pattern() const   { return _node_pattern; }
    const Box *box_pattern() const        { return _box_pattern; }
    const VSLNode *args() const           { return _args()->head(); }
    const VSLNode *body() const           { return _body()->head(); }

    // Compilation
    void compilePatterns(VSLDef *cdef) const;

    // Destroy BOX_PATTERN
    void uncompilePatterns(VSLDef *cdef) const
    {
    CallNode::uncompilePatterns(cdef);

    if (_box_pattern)
        ((LetNode *)this)->_box_pattern->unlink();
    ((LetNode *)this)->_box_pattern = 0;
    }

    // Resolve all names
    int _resolveNames(VSLDef *cdef, unsigned base);

    // Optimization
    int inlineFuncs(VSLDef *cdef, VSLNode **node);
    int _reBase(VSLDef *cdef, unsigned newBase);

    // Copy
    VSLNode *dup() const { return new LetNode(*this); }

    const Box *_eval(ListBox *arglist) const;

    bool isLetNode() const { return true; }

    // Representation invariant
    bool OK() const;
};


// A WhereNode is identical to a LetNode, but is dumped as "where"
// instead of "let".

class WhereNode: public LetNode {
public:
    DECLARE_TYPE_INFO

protected:
    void dump(ostream& s) const;

    // Copy
    WhereNode(WhereNode& node):
    LetNode(node)
    {}

public:
    // Create
    WhereNode(VSLNode *p, VSLNode *a, VSLNode *b):
    LetNode(p, a, b)
    {}
};

#endif