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bsearch()                General Function               bsearch()




Search an array

#iinncclluuddee <ssttddlliibb.hh>
cchhaarr *bbsseeaarrcchh(_k_e_y, _a_r_r_a_y, _n_u_m_b_e_r, _s_i_z_e, _c_o_m_p_a_r_i_s_o_n)
cchhaarr *_k_e_y, *_a_r_r_a_y;
ssiizzee_tt _n_u_m_b_e_r, _s_i_z_e;
iinntt (*_c_o_m_p_a_r_i_s_o_n)();

bbsseeaarrcchh searches a sorted array for a given item.  _i_t_e_m points to
the object sought.  _a_r_r_a_y points to the base of the array; it has
_n_u_m_b_e_r elements, each of  which is _s_i_z_e bytes long.  Its elements
must  be sorted  into ascending  order before  it is  searched by
bbsseeaarrcchh.

_c_o_m_p_a_r_i_s_o_n points  to the function that  compares array elements.
_c_o_m_p_a_r_i_s_o_n  must return  zero if  its  arguments match,  a number
greater than  zero if the  element pointed to by  _a_r_g_1 is greater
than the element pointed to by  _a_r_g_2, and a number less than zero
if  the element  pointed  to by  _a_r_g_1  is less  than the  element
pointed to by _a_r_g_2.

bbsseeaarrcchh returns a pointer to the array element that matches _i_t_e_m.
If no  element matches _i_t_e_m, then bbsseeaarrcchh  returns NULL.  If more
than  one element  within _a_r_r_a_y  matches  _i_t_e_m, which  element is
matched is unspecified.

***** Example *****

This example uses bbsseeaarrcchh to translate English into ``bureaucrat-
ese''.


#include <stdio.h>
#include <stdlib.h>
#include <string.h>



struct syntab {
        char *english, *bureaucratic;
} cdtab[] = {
/* The left column is in alphabetical order */



    "affect",  "impact",
    "after",   "subsequent to",
    "building","physical facility",
    "call",    "refer to as",
    "do",      "implement",






COHERENT Lexicon                                           Page 1




bsearch()                General Function               bsearch()



    "false",   "inoperative",
    "finish",  "finalize",
    "first",   "initial",
    "full",    "in-depth",
    "help",    "facilitate",



    "kill",    "terminate",
    "lie",     "inoperative statement",
    "order",   "prioritize",
    "talk",    "interpersonal communication",
    "then",    "at that point in time",
    "use",     "utilize"
};



int
comparator(key, item)
char *key;
struct syntab *item;
{
    return(strcmp(key, item->english));
}



main()
{
    struct syntab *ans;
    char buf[80];



    for(;;) {
               printf("Enter an English word: ");
               fflush(stdout);



               if(gets(buf) || !strcmp(buf, "quit") == NULL)
               break;



               if((ans = bsearch(buf, (char *)cdtab,
                sizeof(cdtab)/ sizeof(struct syntab),
                sizeof(struct syntab),
                comparator)) == NULL)
               printf("%s not found\n");






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bsearch()                General Function               bsearch()



               else
               printf("Don't say \"%s\"; say \"%s\"!\n",
                ans->english, ans->bureaucratic);
    }
}


***** See Also *****

ggeenneerraall ffuunnccttiioonnss, qqssoorrtt(), ssttddlliibb.hh

***** Notes *****

The  name bbsseeaarrcchh  implies that this  function performs  a binary
search.  A binary search looks  at the midpoint of the array, and
compares  it with  the  element being  sought.   If that  element
matches, then  the work  is done.  If  it does not,  then bbsseeaarrcchh
checks the midpoint  of either the upper half of  the array or of
the lower half, depending  upon whether the midpoint of the array
is larger or smaller than the item being sought.  bbsseeaarrcchh bisects
smaller and smaller regions of  the array until it either finds a
match or can bisect no further.

It is  important that the input _a_r_r_a_y be  sorted, or bbsseeaarrcchh will
not function correctly.
































COHERENT Lexicon                                           Page 3

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