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From: dsr@stl.stc.co.uk (D.S.Riches)
Newsgroups: comp.lang.c
Subject: Re: strings as functions
Message-ID: <3905@stl.stc.co.uk>
Date: 9 Jan 91 09:15:19 GMT
References: <mpapp.663214690@godzilla> <1991Jan7.165639.10403@zoo.toronto.edu> <ertle.663300370@newton>
Sender: news@stl.stc.co.uk
Reply-To: "D.S.Riches" <dsr@stl.stc.co.uk>
Organization: STC Technology Limited, London Road, Harlow, Essex, UK
Lines: 58

>In article <mpapp.663214690@godzilla> mpapp@ (Mike Papper) writes:
>Is there a way to use a string value as the name of a function?
>In other words, can I use a string (possibly
>typed in by a programmer) as a function call to a function of
>the same name?

Tried to reply to you Mike but your path name is corrupted.  See your
Newsmaster about it.

It seems similar to the implementation of a State Transition Model or
Table Driven Software.  E.g.

We define a structure :-

typedef struct sy_s_bed_add_nw_object {
        gen_t_nw_object nw_object;
        STRING          form_name;
        INT             (*func_name)();
        INT             aux_row;
} sy_s_bed_add_nw_object;

Declare a table for it :-

NE_D_EXTERN sy_s_bed_add_nw_object  sy_g_bed_add_table[]
#ifdef DEFINITION
= {
   GEN_D_SITE,          "adsite",       sy_f_bed_Add_Geog_Object, 0,
   GEN_D_BLDG,          "adbldg",       sy_f_bed_Add_Geog_Object, 2,
   GEN_D_LINK,          "adlink",       sy_f_bed_Add_Tx_Object, 3,
   GEN_D_LINK_PT,       "undefined",    dummy,                  -1,
   GEN_D_NODE,          "adnode",       sy_f_bed_Add_Default_Object,
4,
  }
#endif

In this case the structure defines a pointer to a function as the 3rd
element.  In the table we have a name of a function.  We then call
that function by :-

status = (*(sy_g_bed_add_table[i_object_type].func_name))(m_cfmPtr);

Where i_object_type is the 'line_number' corresponding to the nw_object
we're interested in (in State Transitions this would be 
the trigger, we search down a table for the trigger. move across to the action
(funtion) to be called and execute it).

m_cfmPtr is the parameter to this function.

This is taken from a 'live' example, what you might need is similar in
that you could assign a string to the 3rd element and then execute it
... I think.

   Dave Riches
   PSS:    David.S.Riches@stl.stc.co.uk (or dsr@stl.stc.co.uk)
   Smail:  Systems Methods, (Dept. 607, T2 West), 
	   STC Technology Ltd., London Road,
	   Harlow, Essex. CM17 9NA.  England
   Phone:  +44 (0)279-29531 x2496