RexxVariableDictionary.cpp

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/*----------------------------------------------------------------------------*/
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/* Copyright (c) 1995, 2004 IBM Corporation. All rights reserved.             */
/* Copyright (c) 2005-2009 Rexx Language Association. All rights reserved.    */
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/******************************************************************************/
/* REXX Kernel                                   RexxVariableDictionary.cpp   */
/*                                                                            */
/* Primitive Variable Dictionary Class                                        */
/*                                                                            */
/******************************************************************************/
#include "RexxCore.h"
#include "StringClass.hpp"
#include "DirectoryClass.hpp"
#include "RexxNativeActivation.hpp"
#include "RexxActivity.hpp"
#include "ArrayClass.hpp"
#include "ListClass.hpp"
#include "RexxVariableDictionary.hpp"
#include "StemClass.hpp"
#include "ExpressionBaseVariable.hpp"
#include "ExpressionStem.hpp"
#include "ExpressionVariable.hpp"
#include "ExpressionCompoundVariable.hpp"
#include "ExpressionDotVariable.hpp"
#include "ProtectedObject.hpp"
#include "SupplierClass.hpp"
#include "RexxCompoundTail.hpp"
#include "SourceFile.hpp"
 
 
RexxObject  *RexxVariableDictionary::copy()
/******************************************************************************/
/* Function:  Copy a variable dictionary                                      */
/******************************************************************************/
{
    /* create a new object               */
    RexxVariableDictionary *copyObj = new_variableDictionary(contents->mainSlotsSize());
                                         /* copy the behaviour pointer        */
    OrefSet(copyObj, copyObj->behaviour, this->behaviour);
    ProtectedObject p(copyObj);
    /* copy the hash table               */
    OrefSet(copyObj, copyObj->contents, (RexxHashTable *)this->contents->copy());
    /* make sure we copy the scope too */
    OrefSet(copyObj, copyObj->scope, this->scope);
    copyObj->copyValues();               /* copy all of the variables         */
    return(RexxObject *)copyObj;        /* return the new vdict              */
}
 
void RexxVariableDictionary::copyValues()
/******************************************************************************/
/* Function:  Copy all of the values in a vdict                               */
/******************************************************************************/
{
    /* loop through the hash table       */
    for (size_t i = this->contents->first();
        i < this->contents->totalSlotsSize();
        i = this->contents->next(i))
    {
        RexxObject *value = this->contents->value(i);     /* get the next value                */
        RexxObject *copyObj = value->copy();              /* copy the value                    */
        this->contents->replace(copyObj, i);  /* replace with the copied value     */
    }
}
 
RexxObject  *RexxVariableDictionary::realValue(
     RexxString *name)                 /* name of variable to retrieve      */
/******************************************************************************/
/* Function:  Retrieve a variable's value WITHOUT returning the default       */
/*            variable name if it doesn't exist.                              */
/******************************************************************************/
{
    RexxVariable *variable = resolveVariable(name);    /* look up the name                  */
    if (variable == OREF_NULL)           /* not found?                        */
    {
        return OREF_NULL;                  /* say so                            */
    }
    return variable->getVariableValue(); /* use the variable value            */
}
 
 
/**
 * Drop the value of a named variable in the method dictionary.
 *
 * @param name   The string name of the variable.
 */
void RexxVariableDictionary::drop(RexxString *name)
{
    // if the variable exists, drop the value
    RexxVariable *variable = resolveVariable(name);
    if (variable != OREF_NULL)
    {
        variable->drop();
    }
}
 
 
/**
 * Drop the value of a named variable in the method dictionary.
 *
 * @param name   The string name of the variable.
 */
void RexxVariableDictionary::dropStemVariable(RexxString *name)
{
    // if the variable exists, drop the value
    RexxVariable *variable = resolveVariable(name);
    if (variable != OREF_NULL)
    {
        variable->drop();
        /* create a new stem element and set this */
        variable->set(new RexxStem(name));
    }
}
 
 
RexxCompoundElement *RexxVariableDictionary::getCompoundVariable(
     RexxString *stemName,             /* name of stem for compound         */
     RexxObject **tail,                /* tail of the compound element      */
     size_t      tailCount)            /* number of tail pieces             */
/******************************************************************************/
/* Function:  Retrieve a compound variable, returning OREF_NULL if the        */
/*            variable does not exist.                                        */
/******************************************************************************/
{
    /* new tail for compound             */
    RexxCompoundTail resolved_tail(this, tail, tailCount);
 
    RexxStem *stem_table = getStem(stemName);      /* get the stem entry from this dictionary */
    /* get the compound variable         */
    return stem_table->getCompoundVariable(&resolved_tail);
}
 
 
RexxObject *RexxVariableDictionary::getCompoundVariableValue(
     RexxString *stemName,             /* name of stem for compound         */
     RexxObject **tail,                /* tail of the compound element      */
     size_t      tailCount)            /* number of tail pieces             */
/******************************************************************************/
/* Function:  Retrieve a compound variable, returning default value if the    */
/*            variable does not exist.  This does not raise NOVALUE.          */
/******************************************************************************/
{
    /* new tail for compound             */
    RexxCompoundTail resolved_tail(this, tail, tailCount);
 
    RexxStem *stem_table = getStem(stemName);      /* get the stem entry from this dictionary */
    /* get the value from the stem...we pass OREF_NULL */
    /* for the dictionary to bypass NOVALUE handling */
    return stem_table->evaluateCompoundVariableValue(OREF_NULL, stemName, &resolved_tail);
}
 
 
/**
 * Retrieve the "real" value of a compound variable.  This
 * return OREF_NULL for any situation where the compound variable
 * name would be returned.
 *
 * @param stem      The name of the stem.
 * @param tail      The set of tails used for the lookup.
 * @param tailCount The number of tail elements.
 *
 * @return Either the variable value, or OREF_NULL for unassigned
 *         variables.
 */
RexxObject *RexxVariableDictionary::getCompoundVariableRealValue(RexxString *stem,
     RexxObject **tail, size_t tailCount)
{
    /* new tail for compound             */
    RexxCompoundTail resolved_tail(this, tail, tailCount);
 
    RexxStem *stem_table = getStem(stem);          /* get the stem entry from this dictionary */
    /* get the value from the stem...we pass OREF_NULL */
    /* for the dictionary to bypass NOVALUE handling */
    return stem_table->getCompoundVariableRealValue(&resolved_tail);
}
 
 
RexxObject  *RexxVariableDictionary::realStemValue(
     RexxString *stemName)             /* name of stem for compound         */
/******************************************************************************/
/* Function:  Retrieve the "real" value of a stem variable.  OREF_NULL is     */
/*            returned if the stem does not exist.                            */
/******************************************************************************/
{
                                       /* look up the name                  */
  return this->getStem(stemName);      /* find and return the stem directly */
}
 
 
void RexxVariableDictionary::add(
     RexxVariable *variable,           /* new variable entry                */
     RexxString   *name)               /* variable name                     */
/******************************************************************************/
/* Function:  Insert an item into the variable dictionary hash table,         */
/*            updating the lookaside array if the index is available.         */
/******************************************************************************/
{
    /* try to place in existing hashtab  */
    RexxHashTable *new_hash = this->contents->stringAdd((RexxObject *)variable, name);
    if (new_hash != OREF_NULL)           /* have a reallocation occur?        */
    {
        /* hook on the new hash table        */
        OrefSet(this, this->contents, new_hash);
    }
}
 
void RexxVariableDictionary::put(
     RexxVariable *variable,           /* new variable entry                */
     RexxString   *name)               /* variable name                     */
/******************************************************************************/
/* Function:  Insert an item into the variable dictionary hash table,         */
/*            updating the lookaside array if the index is available.         */
/******************************************************************************/
{
    /* try to place in existing hashtab  */
    RexxHashTable *new_hash = this->contents->stringPut((RexxObject *)variable, name);
    if (new_hash != OREF_NULL)           /* have a reallocation occur?        */
    {
        /* hook on the new hash table        */
        OrefSet(this, this->contents, new_hash);
    }
}
 
 
RexxVariable *RexxVariableDictionary::createStemVariable(
     RexxString *stemName)             /* name of target stem               */
/******************************************************************************/
/* Function:  Lookup and retrieve a STEM variable item (not the stem table)   */
/*            level)                                                          */
/******************************************************************************/
{
    RexxVariable *variable =  new_variable(stemName); /* make a new variable entry         */
    RexxStem *stemtable = new RexxStem (stemName); /* create a stem object as value     */
    /* the stem object is the value of   */
    /* stem variable                     */
    variable->set((RexxObject *)stemtable);
    /* try to place in existing hashtab  */
    RexxHashTable *new_hash = this->contents->stringAdd((RexxObject *)variable, stemName);
    if (new_hash != OREF_NULL)         /* have a reallocation occur?        */
    {
        /* hook on the new hash table        */
        OrefSet(this, this->contents, new_hash);
    }
    return variable;                     /* return the stem                   */
}
 
 
RexxVariable  *RexxVariableDictionary::createVariable(
     RexxString *name)                 /* name of target variable           */
/******************************************************************************/
/* Function:  Create a new variable item and add it to the dictionary.        */
/******************************************************************************/
{
    RexxVariable *variable =  new_variable(name);      /* make a new variable entry         */
    /* try to place in existing hashtab  */
    RexxHashTable *new_hash = this->contents->stringAdd((RexxObject *)variable, name);
    if (new_hash != OREF_NULL)           /* have a reallocation occur?        */
    {
        /* hook on the new hash table        */
        OrefSet(this, this->contents, new_hash);
    }
    return variable;                     /* return the stem                   */
}
 
RexxVariable *RexxVariableDictionary::nextVariable(
  RexxNativeActivation *activation)    /* Hosting Native Act.               */
/******************************************************************************/
/* Function:  Return the "next" variable of a variable traversal              */
/******************************************************************************/
{
    if (activation->nextVariable() == SIZE_MAX)/* first time through?               */
    {
        /* get the first item                */
        activation->setNextVariable(this->contents->first());
    }
    else                                 /* step to the next index item       */
    {
        activation->setNextVariable(this->contents->next(activation->nextVariable()));
    }
    /* while more directory entries      */
    while (this->contents->index(activation->nextVariable()) != OREF_NULL)
    {
        /* get the variable object           */
        RexxVariable *variable = (RexxVariable *)this->contents->value(activation->nextVariable());
        /* get the value                     */
        RexxObject *value = variable->getVariableValue();
        if (value != OREF_NULL)
        {          /* not a dropped variable?           */
            return variable;               /* got what we need                  */
        }
        /* step to the next index item       */
        activation->setNextVariable(this->contents->next(activation->nextVariable()));
    }
    activation->setNextVariable(-1);     /* reset the index for the end       */
    return OREF_NULL;
}
 
void RexxVariableDictionary::set(
     RexxString *name,                 /* name to set                       */
     RexxObject *value)                /* value to assign to variable name  */
/******************************************************************************/
/* Function:  Set a new variable value                                        */
/******************************************************************************/
{
    RexxVariable *variable;              /* retrieved variable item           */
 
    variable = getVariable(name);        /* look up the name                  */
    variable->set(value);                /* and perform the set               */
}
 
void RexxVariableDictionary::reserve(
  RexxActivity *activity)              /* reserving activity                */
/******************************************************************************/
/* Function:  Reserve a scope on an object, waiting for completion if this    */
/*            is already reserved by another activity                         */
/******************************************************************************/
{
    /* currently unlocked?               */
    if (this->reservingActivity == OREF_NULL)
    {
        /* set the locker                    */
        OrefSet(this, this->reservingActivity, activity);
        this->reserveCount = 1;            /* we're reserved once               */
    }
    /* doing again on the same stack?    */
    else if (this->reservingActivity == activity)
    {
        this->reserveCount++;              /* bump the nesting count            */
    }
    else
    {                               /* need to wait on this              */
                                    /* go perform dead lock checks       */
        this->reservingActivity->checkDeadLock(activity);
        /* no list here?                     */
        if (this->waitingActivities == OREF_NULL)
        {
            /* get a waiting queue               */
            OrefSet(this, this->waitingActivities, new_list());
        }
        /* add to the wait queue             */
        this->waitingActivities->addLast((RexxObject *)activity);
        /* ok, now we wait                   */
        activity->waitReserve((RexxObject *)this);
    }
}
 
void RexxVariableDictionary::release(
  RexxActivity *activity)              /* reserving activity                */
/******************************************************************************/
/* Function:  Release the lock on an object's ovd                             */
/******************************************************************************/
{
    this->reserveCount--;                /* decrement the reserving count     */
    if (this->reserveCount == 0)
    {       /* last one for this activity?       */
            /* remove the current reserver       */
        OrefSet(this, this->reservingActivity, OREF_NULL);
        /* have things waiting?              */
        if (this->waitingActivities != OREF_NULL)
        {
            /* get the next one                  */
            RexxActivity *newActivity = (RexxActivity *)this->waitingActivities->removeFirst();
            /* have a real one here?             */
            if (newActivity != (RexxActivity *)TheNilObject)
            {
                /* this is the new owner             */
                OrefSet(this, this->reservingActivity, newActivity);
                this->reserveCount = 1;        /* back to one lock again            */
                                               /* wake up the waiting activity      */
                newActivity->postDispatch();
            }
        }
    }
}
 
 
bool RexxVariableDictionary::transfer(
  RexxActivity *activity)              /* new reserving activity            */
/******************************************************************************/
/* Function:  Transfer a vdict lock to another activity                       */
/******************************************************************************/
{
    if (this->reserveCount == 1)
    {       /* only one level of nesting?        */
            /* easy, just switch the owner       */
        OrefSet(this, this->reservingActivity, activity);
        return true;                       /* say this worked                   */
    }
    else
    {                               /* multiple nesting levels           */
        this->release(activity);           /* release this lock                 */
        return false;                      /* can't do this                     */
    }
}
 
 
void RexxVariableDictionary::setNextDictionary(RexxVariableDictionary *_next)
/******************************************************************************/
/* Function:  Chain up a dictionary associated with an object                 */
/******************************************************************************/
{
    OrefSet(this, this->next, _next);
}
 
void RexxVariableDictionary::live(size_t liveMark)
/******************************************************************************/
/* Function:  Normal garbage collection live marking                          */
/******************************************************************************/
{
  memory_mark(this->contents);
  memory_mark(this->reservingActivity);
  memory_mark(this->waitingActivities);
  memory_mark(this->next);
  memory_mark(this->scope);
}
 
void RexxVariableDictionary::liveGeneral(int reason)
/******************************************************************************/
/* Function:  Generalized object marking                                      */
/******************************************************************************/
{
  memory_mark_general(this->contents);
  memory_mark_general(this->reservingActivity);
  memory_mark_general(this->waitingActivities);
  memory_mark_general(this->next);
  memory_mark_general(this->scope);
}
 
 
/**
 * Get all of the variables in the local context.  This returns
 * just the top-level variables (i.e., simple variables and stems).
 *
 * @return A supplier for iterating the variable sset.
 */
RexxDirectory *RexxVariableDictionary::getAllVariables()
{
    HashLink i;
    RexxDirectory *result = new_directory();
    ProtectedObject p1(result);
                                         /* loop through the hash table       */
    for (i = this->contents->first();
         i < this->contents->totalSlotsSize();
         i = this->contents->next(i))
    {
        // get the next variable from the dictionary
        RexxVariable *variable = (RexxVariable *)this->contents->value(i);
        // if this variable has a value, bump the count
        if (variable->getVariableValue() != OREF_NULL)
        {
            result->put(variable->getVariableValue(), variable->getName());
        }
    }
 
    return result;
}
 
 
void RexxVariableDictionary::flatten(RexxEnvelope *envelope)
/******************************************************************************/
/* Function:  Flatten an object                                               */
/******************************************************************************/
{
  setUpFlatten(RexxVariableDictionary)
 
   flatten_reference(newThis->contents, envelope);
   flatten_reference(newThis->reservingActivity, envelope);
   flatten_reference(newThis->waitingActivities, envelope);
   flatten_reference(newThis->next, envelope);
   flatten_reference(newThis->scope, envelope);
  cleanUpFlatten
}
 
 
RexxVariableDictionary *RexxVariableDictionary::newInstance(
     size_t looksize)                  /* expected size of the vdict        */
/******************************************************************************/
/* Function:  Create a new translator object                                  */
/******************************************************************************/
{
                                       /* Get new object                    */
                                       /* NOTE:  there is one extra         */
                                       /* lookaside element allocated,      */
                                       /* which is used for non-lookaside   */
                                       /* lookups.  Using this extra element*/
                                       /* (which is always NULL), allows    */
                                       /* some special optimization of the  */
                                       /* look ups                          */
                                       /* get a new object and hash         */
  return (RexxVariableDictionary *)new_hashCollection(looksize * 2, sizeof(RexxVariableDictionary), T_VariableDictionary);
}
 
 
RexxVariableDictionary *RexxVariableDictionary::newInstance(
     RexxObject *scope)                /* expected size of the vdict        */
/******************************************************************************/
/* Function:  Create a new translator object                                  */
/******************************************************************************/
{
    /* create entries for twice size     */
    size_t hashTabSize = DEFAULT_OBJECT_DICTIONARY_SIZE * 2;
    /* Get new object                    */
    /* NOTE:  there is one extra         */
    /* lookaside element allocated,      */
    /* which is used for non-lookaside   */
    /* lookups.  Using this extra element*/
    /* (which is always NULL), allows    */
    /* some special optimization of the  */
    /* look ups                          */
    /* get a new object and hash         */
    RexxVariableDictionary *newObj = (RexxVariableDictionary *)new_hashCollection(hashTabSize, sizeof(RexxVariableDictionary), T_VariableDictionary);
    newObj->scope = scope;               /* fill in the scope */
    return newObj;                       /* return the new vdict              */
}
 
 
/**
 * Set a compound variable in the dictionary.
 *
 * @param stemName  The name of the stem.
 * @param tail      The tail elements.
 * @param tailCount The count of tail elements.
 * @param value     The value to set.
 */
void RexxVariableDictionary::setCompoundVariable(RexxString *stemName, RexxObject **tail, size_t tailCount, RexxObject *value)
{
                                         /* new tail for compound             */
    RexxCompoundTail resolved_tail(this, tail, tailCount);
 
    RexxStem *stem_table = getStem(stemName);      /* get the stem entry from this dictionary */
                                         /* and set the value                 */
    stem_table->setCompoundVariable(&resolved_tail, value);
}
 
 
/**
 * Drop a compound variable in the dictionary.
 *
 * @param stemName  The name of the stem.
 * @param tail      The tail elements.
 * @param tailCount The count of tail elements.
 * @param value     The value to set.
 */
void RexxVariableDictionary::dropCompoundVariable(RexxString *stemName, RexxObject **tail, size_t tailCount)
{
                                         /* new tail for compound             */
    RexxCompoundTail resolved_tail(this, tail, tailCount);
 
    RexxStem *stem_table = getStem(stemName);      /* get the stem entry from this dictionary */
                                         /* and set the value                 */
    stem_table->dropCompoundVariable(&resolved_tail);
}
 
 
RexxVariableBase  *RexxVariableDictionary::getVariableRetriever(
     RexxString  *variable )           /* name of the variable              */
/******************************************************************************/
/* Arguments:  Name of variable to generate retriever                         */
/*                                                                            */
/*  Returned:  Retriever for variable (returns OREF_NULL for invalids)        */
/******************************************************************************/
{
    variable = variable->upper();        /* upper case the variable           */
    ProtectedObject p(variable);
    int type = variable->isSymbol();         /* validate the symbol               */
    /* create a retriever object         */
    switch (type)
    {
        case STRING_BAD_VARIABLE:          /* if it didn't validate             */
            return OREF_NULL;                /* don't return a retriever object   */
 
        case STRING_LITERAL_DOT:           /* if is is a literal                */
        case STRING_NUMERIC:
            /* these are literals                */
            return(RexxVariableBase *)variable;
 
            // Dot variables retrieve from the environment
        case STRING_LITERAL:
            // this is only a dot variable if it begins with a period
            if (variable->getChar(0) == '.')
            {
                return (RexxVariableBase *)new RexxDotVariable(variable->extract(1, variable->getLength() - 1));
            }
            // this is a literal symbol not beginning with a period
            return (RexxVariableBase *)variable;
 
            /* if it is a stem                   */
        case STRING_STEM:
            /* create a new stem retriever       */
            return(RexxVariableBase *)new RexxStemVariable(variable, 0);
            /* if it is a compound               */
        case STRING_COMPOUND_NAME:
            /* create a new compound retriever   */
            return(RexxVariableBase *)buildCompoundVariable(variable, false);
            /* if it is a simple                 */
        case STRING_NAME:
            /* create a new variable retriever   */
            return(RexxVariableBase *)new RexxParseVariable(variable, 0);
            /* if we don't know what it is       */
        default:
            return OREF_NULL;                /* don't return a retriever object   */
    }
}
 
 
RexxVariableBase  *RexxVariableDictionary::getDirectVariableRetriever(
     RexxString *variable )            /* name of the variable              */
/******************************************************************************/
/* Function:  Return a retriever for a variable using direct access (i.e.     */
/*            no substitution in compound variable tails)                     */
/******************************************************************************/
{
    size_t length = variable->getLength();      /* get the name length               */
    /* get the first character           */
    codepoint_t character = variable->getChar(0);
    bool        literal = false;         /* literal indicator                 */
                                         /* constant symbol?                  */
    if (character == '.' || (character >= '0' && character <= '9'))
    {
        literal = true;                    /* this is a literal value           */
    }
                                           /* have a valid length?              */
    if (length <= (size_t)MAX_SYMBOL_LENGTH && length > 0)
    {
        size_t compound = 0;                      /* no periods yet                    */
        size_t scan = 0;                          /* start at string beginning         */
        size_t nonnumeric = 0;                    /* count of non-numeric characters   */
        codepoint_t last = 0;                            /* no last character                 */
        while (scan < length)
        {
            /* get the next character            */
            character = variable->getChar(scan);
            /* have a period?                    */
            if (character == '.')
            {
                if (!literal)                  /* not a literal value?              */
                {
                    /* don't process past here           */
                    return(RexxVariableBase *)buildCompoundVariable(variable, true);
                }
                else
                {
                    compound++;                  /* count the character               */
                }
            }
            /* may have a special character      */
            else if (!RexxSource::isSymbolCharacter(character))
            {
                /* maybe exponential form?           */
                if (character == '+' || character == '-')
                {
                    /* front part not valid?             */
                    if (compound > 1 || nonnumeric > 1 || last != 'E')
                    {
                        return OREF_NULL;          /* got a bad symbol                  */
                    }
                    scan++;                      /* step over the sign                */
                    if (scan >= length)          /* sign as last character?           */
                    {
                        return OREF_NULL;          /* this is bad also                  */
                    }
                    /* scan remainder                    */
                    while (scan < length)
                    {
                        /* get the next character            */
                        character = variable->getChar(scan);
                        /* outside numeric range?            */
                        if (character < '0' || character > '9')
                        {
                            return OREF_NULL;        /* not valid either                  */
                        }
                        scan++;                    /* step scan position                */
                    }
                    break;                       /* done with scanning                */
                }
                else
                {
                    // invalid character in a symbol
                    return OREF_NULL;
                }
            }
            /* non-numeric character?            */
            else if (character < '0' || character > '9')
            {
                nonnumeric++;                  /* count the non-numeric             */
            }
                                               /* lower case character?             */
            else if (RexxSource::translateChar(character) != character)
            {
                return OREF_NULL;              /* this is bad, return               */
            }
            last = character;                /* remember last one                 */
            scan++;                          /* step the pointer                  */
        }
    }
    if (literal)                         /* was this a literal?               */
    {
        /* these are both just literals      */
        return(RexxVariableBase *)variable;
    }
    else                                 /* simple variable                   */
    {
        /* create a new variable retriever   */
        return(RexxVariableBase *)new RexxParseVariable(variable, 0);
    }
}
 
 
RexxObject *RexxVariableDictionary::buildCompoundVariable(
    RexxString *variable_name,          /* full variable name of compound    */
    bool direct)                        /* this is direct access             */
/******************************************************************************/
/* Function:  Build a dynamically created compound variable                   */
/******************************************************************************/
{
    size_t length = variable_name->getLength();      /* get the string length             */
    size_t position = 0;                        /* start scanning at first character */
    /* scan to the first period          */
    while (variable_name->getChar(position) != '.')
    {
        position++;                        /* step to the next character        */
        length--;                          /* reduce the length also            */
    }
    /* extract the stem part             */
    RexxString *stem = variable_name->extract(0, position + 1);
    ProtectedObject p(stem);
    /* processing to decompose the name  */
    /* into its component parts          */
 
    RexxQueue *tails = new_queue();      /* get a new list for the tails      */
    ProtectedObject p1(tails);
    position++;                          /* step past previous period         */
    length--;                            /* adjust the length                 */
    /* direct access?                    */
    if (direct == true)
    {
        /* extract the tail part             */
        RexxString *tail = variable_name->extract(position, length);
        tails->push(tail);                 /* add to the tail piece list        */
    }
    else
    {
        size_t endPosition = position + length;
 
        while (position < endPosition)     /* process rest of the variable      */
        {
            size_t start = position;                /* save the start position           */
                                             /* scan for the next period          */
            while (position < endPosition && variable_name->getChar(position) != '.')
            {
                position++;                    /* step to the next character        */
            }
            /* extract the tail part             */
            RexxString *tail = variable_name->extract(start, position - start);
            /* have a null tail piece or         */
            /* section begin with a digit?       */
            /* ASCII '0' to '9' to recognize a digit                              */
 
            RexxObject *tailPart;
            if (tail->getLength() == 0 || (tail->getChar(0) >= '0' && tail->getChar(0) <= '9'))
            {
                tailPart = (RexxObject *)tail; /* this is a literal piece           */
            }
            else
            {
                /* create a new variable retriever   */
                tailPart = (RexxObject *)new RexxParseVariable(tail, 0);
            }
            tails->push(tailPart);           /* add to the tail piece list        */
            position++;                      /* step past previous period         */
        }
        /* have a trailing period?           */
        if (variable_name->getChar(position - 1) == '.')
        {
            tails->push(OREF_NULLSTRING);    /* add to the tail piece list        */
        }
    }
    /* create and return a new compound  */
    return(RexxObject *)new (tails->getSize()) RexxCompoundVariable(variable_name, stem, 0, tails, tails->getSize());
}