method

index

v1_8_7_330 - Show latest stable - Class: String

index(...)

public

Returns the index of the first occurrence of the given substring, character (fixnum), or pattern (regexp) in str. Returns nil if not found. If the second parameter is present, it specifies the position in the string to begin the search.

"hello".index('e')             #=> 1
"hello".index('lo')            #=> 3
"hello".index('a')             #=> nil
"hello".index(101)             #=> 1
"hello".index(/[aeiou]/, -3)   #=> 4

/*
 *  call-seq:
 *     str.index(substring [, offset])   => fixnum or nil
 *     str.index(fixnum [, offset])      => fixnum or nil
 *     str.index(regexp [, offset])      => fixnum or nil
 *  
 *  Returns the index of the first occurrence of the given <i>substring</i>,
 *  character (<i>fixnum</i>), or pattern (<i>regexp</i>) in <i>str</i>. Returns
 *  <code>nil</code> if not found. If the second parameter is present, it
 *  specifies the position in the string to begin the search.
 *     
 *     "hello".index('e')             #=> 1
 *     "hello".index('lo')            #=> 3
 *     "hello".index('a')             #=> nil
 *     "hello".index(101)             #=> 1
 *     "hello".index(/[aeiou]/, -3)   #=> 4
 */

static VALUE
rb_str_index_m(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    VALUE sub;
    VALUE initpos;
    long pos;

    if (rb_scan_args(argc, argv, "11", &sub, &initpos) == 2) {
        pos = NUM2LONG(initpos);
    }
    else {
        pos = 0;
    }
    if (pos < 0) {
        pos += RSTRING(str)->len;
        if (pos < 0) {
            if (TYPE(sub) == T_REGEXP) {
                rb_backref_set(Qnil);
            }
            return Qnil;
        }
    }

    switch (TYPE(sub)) {
      case T_REGEXP:
        pos = rb_reg_adjust_startpos(sub, str, pos, 0);
        pos = rb_reg_search(sub, str, pos, 0);
        break;

      case T_FIXNUM: {
        int c = FIX2INT(sub);
        long len = RSTRING(str)->len;
        unsigned char *p = (unsigned char*)RSTRING(str)->ptr;

        for (;pos<len;pos++) {
            if (p[pos] == c) return LONG2NUM(pos);
        }
        return Qnil;
      }

      default: {
        VALUE tmp;

        tmp = rb_check_string_type(sub);
        if (NIL_P(tmp)) {
            rb_raise(rb_eTypeError, "type mismatch: %s given",
                     rb_obj_classname(sub));
        }
        sub = tmp;
      }
        /* fall through */
      case T_STRING:
        pos = rb_str_index(str, sub, pos);
        break;
    }

    if (pos == -1) return Qnil;
    return LONG2NUM(pos);
}

index

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