NAME
	parse_command - try to match a string with a given pattern

SYNOPSIS
	int parse_command(string command, object env|object *oblist,
			  string pattern, mixed arg, ...)

DESCRIPTION
  This is one of the most complex efun in LPmud to use. It takes
  some effort to learn and use, but when mastered, very powerfull constructs
  can be implemented.

  Basically parse_command() is a piffed up sscanf operating on word basis. It
  works similar to sscanf in that it takes a pattern and a variable set of
  destination arguments. It is together with sscanf the only efun to use
  pass by reference for other variables than arrays.

  To make the efun usefull it must have a certain support from the mudlib,
  there is a set of functions that it needs to call to get relevant
  information before it can parse in a sensible manner.

  In earlier versions it used the normal id() lfun in the LPC objects to
  find out if a given object was identified by a certain string. This was
  highly inefficient as it could result in hundreds or maybe thousands of
  calls when very long commands were parsed. 
  
  The new version relies on the LPC objects to give it three lists of 'names'.

       1 - The normal singular names.
       2 - The plural forms of the names.
       3 - The acknowledged adjectives of the object.

  These are fetched by calls to the functions:

       1 - string *parse_command_id_list();
       2 - string *parse_command_plural_id_list();
       3 - string *parse_command_adjectiv_id_list();

  The only really needed list is the first. If the second does not exist
  than the efun will try to create one from the singluar list. For 
  grammatical reasons it does not always succeed in a perfect way. This is
  especially true when the 'names' are not single words but phrases.

  The third is very nice to have because it makes constructs like
  'get all the little blue ones' possible.

  Apart from these functions that should exist in all objects, and which
  are therefore best put in /std/object.c there is also a set of functions
  needed in /secure/master.c These are not absolutely necessary but they
  give extra power to the efun.

  Basically these /secure/master.c lfuns are there to give default values
  for the lists of names fetched from each object.

  The names in these lists are applicable to any and all objects, the first
  three are identical to the lfun's in the objects:

       string *parse_command_id_list()
                - Would normally return: ({ "one", "thing" })

       string *parse_command_plural_id_list()
                - Would normally return: ({ "ones", "things", "them" })

       string *parse_command_adjectiv_id_list()
                - Would normally return ({ "iffish" })

  The last two are the default list of the prepositions and a single so called
  'all' word. 

       string *parse_command_prepos_list()
                 - Would normally return: ({ "in", "on", "under" })

       string parse_command_all_word()
                 - Would normally return: "all"


  The function returns 1 if 'command' is considered to have matched 'pattern'.
  The 'env' or 'oblist' parameter either holds an object or a list of objects.
  If it holds a single object than a list of objects are automatically
  created by adding the deep_inventory of the object, ie this is identical:

	parse_command(cmd, environment(), pattern, arg)

			and
	parse_command(cmd, ({ environment() }) + deep_inventory(environment()),
		      pattern, arg)

  'pattern' is a list of words and formats:

	Example string = " 'get' / 'take' %i "
	Syntax:
		'word' 		obligatory text
		[word]		optional text
		/		Alternative marker
		%o		Single item, object
		%l		Living objects
		%s		Any text
		%w              Any word
		%p		One of a list (prepositions)
		%i		Any items
		%d              Number 0- or tx(0-99)

    The 'arg' list is zero or more arguments. These are the result variables
    as in sscanf. Note that one variable is needed for each %_

	The return types of different %_ is:
		%o	Returns an object
		%s	Returns a string of words
		%w      Returns a string of one word
		%p	Can on entry hold a list of word in array
			or an empty variable
			Returns:
			   if empty variable: a string
			   if array: array[0]=matched word
		%i	Returns a special array on the form:
			[0] = (int) +(wanted) -(order) 0(all)
			[1..n] (object) Objectpointers	
		%l	Returns a special array on the form:
			[0] = (int) +(wanted) -(order) 0(all)
			[1..n] (object) Objectpointers
			                These are only living objects.
		%d      Returns a number

  The only types of % that uses all the loaded information from the objects
  are %i and %l. These are in fact identical except that %l filters out
  all nonliving objects from the list of objects before trying to parse.

  The return values of %i and %l is also the most complex. They return an
  array consisting of first a number and then all possible objects matching.
  As the typical string matched by %i/%l looks like: 'three red roses',
  'all nasty bugs' or 'second blue sword' the number indicates which 
  of these numerical constructs was matched:

         if numeral >0 then three, four, five etc were matched
         if numeral <0 then second, twentyfirst etc were matched
         if numeral==0 then 'all' or a generic plural form such as 'apples'
                            were matched.

  NOTE!
       The efun makes no semantic implication on the given numeral. It does
       not matter if 'all apples' or 'second apple' is given. A %i will
       return ALL possible objects matching in the array. It is up to the
       caller to decide what 'second' means in a given context.

       Also when given an object and not an explicit array of objects the
       entire recursive inventory of the given object is searched. It is up
       to the caller to decide which of the objects are actually visible
       meaning that 'second' might not at all mean the second object in
       the returned array of objects.
			

SEE ALSO
	sscanf, deep_inventory

CAVEAT
	Patterns of type: "%s %w %i"
	Might not work as one would expect. %w will always succeed so the arg
	corresponding to %s will always be empty.

BUGS
	Patterns of the type: 'word' and [word]
	The 'word' can not contain spaces. It must be a single word. 
	This is so because the pattern is exploded on " " (space) and a
	pattern element can therefore not contain spaces.

EXAMPLE:

	 if (parse_command("spray car",environment(this_player()),
        	              " 'spray' / 'paint' [paint] %i ",items))  
	 {	
	    /*
	      If the pattern matched then items holds a return array as
	      described under 'destargs' %i above.
     	    */
	 }

