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