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Annotation of 43BSD/contrib/icon/functions/bal.c, revision 1.1.1.1

1.1       root        1: #include "../h/rt.h"
                      2: 
                      3: /*
                      4:  * bal(c1,c2,c3,s,i,j) - find end of a balanced substring of s[i:j].
                      5:  *  Generates successive positions.
                      6:  */
                      7: 
                      8: Xbal(nargs, arg6, arg5, arg4, arg3, arg2, arg1, arg0)
                      9: int nargs;
                     10: struct descrip arg6, arg5, arg4, arg3, arg2, arg1, arg0;
                     11:    {
                     12:    register int i, j, cnt;
                     13:    register c;
                     14:    int t;
                     15:    long l1, l2;
                     16:    int *cs1, *cs2, *cs3;
                     17:    int csbuf1[CSETSIZE], csbuf2[CSETSIZE], csbuf3[CSETSIZE];
                     18:    char sbuf[MAXSTRING];
                     19:    static int lpar[CSETSIZE] = /* '(' */
                     20:       cset_display(0, 0, 0400, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
                     21:    static int rpar[CSETSIZE] = /* ')' */
                     22:       cset_display(0, 0, 01000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
                     23: 
                     24:    /*
                     25:     *  c1 defaults to &cset; c2 defaults to '(' (lpar); c3 defaults to
                     26:     *   ')' (rpar); s to &subject; i to &pos if s defaulted, 1 otherwise;
                     27:     *   j defaults to 0.
                     28:     */
                     29:    defcset(&arg1, &cs1, csbuf1, k_cset.bits);
                     30:    defcset(&arg2, &cs2, csbuf2, lpar);
                     31:    defcset(&arg3, &cs3, csbuf3, rpar);
                     32:    if (defstr(&arg4, sbuf, &k_subject))
                     33:       defint(&arg5, &l1, k_pos);
                     34:    else
                     35:       defint(&arg5, &l1, 1);
                     36:    defint(&arg6, &l2, 0);
                     37: 
                     38:    /*
                     39:     * Convert i and j to positions in s and order them.
                     40:     */
                     41:    i = cvpos(l1, STRLEN(arg4));
                     42:    j = cvpos(l2, STRLEN(arg4));
                     43:    if (i > j) {
                     44:       t = i;
                     45:       i = j;
                     46:       j = t;
                     47:       }
                     48: 
                     49:    /*
                     50:     * Loop through characters in s[i:j].  When a character in cs2 is
                     51:     *  found, increment cnt; when a chracter in cs3 is found, decrement
                     52:     *  cnt.  When cnt is 0 there have been an equal number of occurrences
                     53:     *  of characters in cs2 and cs3, i.e., the string to the left of
                     54:     *  i is balanced.  If the string is balanced and the current character
                     55:     *  (s[i]) is in c1, suspend i.  Note that if cnt drops below zero,
                     56:     *  bal fails.
                     57:     */
                     58:    cnt = 0;
                     59:    while (i < j) {
                     60:       c = STRLOC(arg4)[i-1];
                     61:       if (cnt == 0 && tstb(c, cs1)) {
                     62:          arg0.type = D_INTEGER;
                     63:          INTVAL(arg0) = i;
                     64:          suspend();
                     65:          }
                     66:       if (tstb(c, cs2))
                     67:          cnt++;
                     68:       else if (tstb(c, cs3))
                     69:          cnt--;
                     70:       if (cnt < 0)
                     71:          fail();
                     72:       i++;
                     73:       }
                     74:    /*
                     75:     * Eventually fail.
                     76:     */
                     77:    fail();
                     78:    }
                     79: 
                     80: Procblock(bal,6)

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