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Range

A Range represents an interval—a set of values with a beginning and an end. Ranges may be constructed using the s..e and s...e literals, or with Range::new. Ranges constructed using .. run from the beginning to the end inclusively. Those created using ... exclude the end value. When used as an iterator, ranges return each value in the sequence.

(-1..-5).to_a      #=> []
(-5..-1).to_a      #=> [-5, -4, -3, -2, -1]
('a'..'e').to_a    #=> ["a", "b", "c", "d", "e"]
('a'...'e').to_a   #=> ["a", "b", "c", "d"]

Custom Objects in Ranges¶ ↑

Ranges can be constructed using any objects that can be compared using the <=> operator. Methods that treat the range as a sequence (each and methods inherited from Enumerable) expect the begin object to implement a succ method to return the next object in sequence. The step and include? methods require the begin object to implement succ or to be numeric.

In the Xs class below both <=> and succ are implemented so Xs can be used to construct ranges. Note that the Comparable module is included so the == method is defined in terms of <=>.

class Xs                # represent a string of 'x's
  include Comparable
  attr :length
  def initialize(n)
    @length = n
  end
  def succ
    Xs.new(@length + 1)
  end
  def <=>(other)
    @length <=> other.length
  end
  def to_s
    sprintf "%2d #{inspect}", @length
  end
  def inspect
    'x' * @length
  end
end

An example of using Xs to construct a range:

r = Xs.new(3)..Xs.new(6)   #=> xxx..xxxxxx
r.to_a                     #=> [xxx, xxxx, xxxxx, xxxxxx]
r.member?(Xs.new(5))       #=> true

Public Class Methods

new(begin, end, exclude_end=false) → rng click to toggle source

Constructs a range using the given begin and end. If the exclude_end parameter is omitted or is false, the rng will include the end object; otherwise, it will be excluded.

 
               static VALUE
range_initialize(int argc, VALUE *argv, VALUE range)
{
    VALUE beg, end, flags;

    rb_scan_args(argc, argv, "21", &beg, &end, &flags);
    range_modify(range);
    range_init(range, beg, end, RBOOL(RTEST(flags)));
    return Qnil;
}

Public Instance Methods

rng == obj → true or false click to toggle source

Returns true only if obj is a Range, has equivalent begin and end items (by comparing them with ==), and has the same exclude_end? setting as the range.

(0..2) == (0..2)            #=> true
(0..2) == Range.new(0,2)    #=> true
(0..2) == (0...2)           #=> false

 
               static VALUE
range_eq(VALUE range, VALUE obj)
{
    if (range == obj)
        return Qtrue;
    if (!rb_obj_is_kind_of(obj, rb_cRange))
        return Qfalse;

    return rb_exec_recursive_paired(recursive_equal, range, obj, obj);
}

rng === obj → true or false click to toggle source

Returns true if obj is an element of the range, false otherwise. Conveniently, === is the comparison operator used by case statements.

case 79
when 1..50   then   print "low\n"
when 51..75  then   print "medium\n"
when 76..100 then   print "high\n"
end

produces:

high

 
               static VALUE
range_eqq(VALUE range, VALUE val)
{
    return rb_funcall(range, rb_intern("include?"), 1, val);
}

begin → obj click to toggle source

Returns the object that defines the beginning of the range.

(1..10).begin   #=> 1

 
               static VALUE
range_begin(VALUE range)
{
    return RANGE_BEG(range);
}

bsearch {|obj| block } → value click to toggle source

By using binary search, finds a value in range which meets the given condition in O(log n) where n is the size of the range.

You can use this method in two use cases: a find-minimum mode and a find-any mode. In either case, the elements of the range must be monotone (or sorted) with respect to the block.

In find-minimum mode (this is a good choice for typical use case), the block must return true or false, and there must be a value x so that:

the block returns false for any value which is less than x, and
the block returns true for any value which is greater than or equal to x.

If x is within the range, this method returns the value x. Otherwise, it returns nil.

ary = [0, 4, 7, 10, 12]
(0...ary.size).bsearch {|i| ary[i] >= 4 } #=> 1
(0...ary.size).bsearch {|i| ary[i] >= 6 } #=> 2
(0...ary.size).bsearch {|i| ary[i] >= 8 } #=> 3
(0...ary.size).bsearch {|i| ary[i] >= 100 } #=> nil

(0.0...Float::INFINITY).bsearch {|x| Math.log(x) >= 0 } #=> 1.0

In find-any mode (this behaves like libc's bsearch(3)), the block must return a number, and there must be two values x and y (x <= y) so that:

the block returns a positive number for v if v < x,
the block returns zero for v if x <= v < y, and
the block returns a negative number for v if y <= v.

This method returns any value which is within the intersection of the given range and x…y (if any). If there is no value that satisfies the condition, it returns nil.

ary = [0, 100, 100, 100, 200]
(0..4).bsearch {|i| 100 - ary[i] } #=> 1, 2 or 3
(0..4).bsearch {|i| 300 - ary[i] } #=> nil
(0..4).bsearch {|i|  50 - ary[i] } #=> nil

You must not mix the two modes at a time; the block must always return either true/false, or always return a number. It is undefined which value is actually picked up at each iteration.

 
               static VALUE
range_bsearch(VALUE range)
{
    VALUE beg, end, satisfied = Qnil;
    int smaller;

    /* Implementation notes:
     * Floats are handled by mapping them to 64 bits integers.
     * Apart from sign issues, floats and their 64 bits integer have the
     * same order, assuming they are represented as exponent followed
     * by the mantissa. This is true with or without implicit bit.
     *
     * Finding the average of two ints needs to be careful about
     * potential overflow (since float to long can use 64 bits)
     * as well as the fact that -1/2 can be 0 or -1 in C89.
     *
     * Note that -0.0 is mapped to the same int as 0.0 as we don't want
     * (-1...0.0).bsearch to yield -0.0.
     */

#define BSEARCH_CHECK(expr) \
    do { \
        VALUE val = (expr); \
        VALUE v = rb_yield(val); \
        if (FIXNUM_P(v)) { \
            if (v == INT2FIX(0)) return val; \
            smaller = (SIGNED_VALUE)v < 0; \
        } \
        else if (v == Qtrue) { \
            satisfied = val; \
            smaller = 1; \
        } \
        else if (v == Qfalse || v == Qnil) { \
            smaller = 0; \
        } \
        else if (rb_obj_is_kind_of(v, rb_cNumeric)) { \
            int cmp = rb_cmpint(rb_funcall(v, id_cmp, 1, INT2FIX(0)), v, INT2FIX(0)); \
            if (!cmp) return val; \
            smaller = cmp < 0; \
        } \
        else { \
            rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE \
                     " (must be numeric, true, false or nil)", \
                     rb_obj_class(v)); \
        } \
    } while (0)

#define BSEARCH(conv) \
    do { \
        RETURN_ENUMERATOR(range, 0, 0); \
        if (EXCL(range)) high--; \
        org_high = high; \
        while (low < high) { \
            mid = ((high < 0) == (low < 0)) ? low + ((high - low) / 2) \
                : (low < -high) ? -((-1 - low - high)/2 + 1) : (low + high) / 2; \
            BSEARCH_CHECK(conv(mid)); \
            if (smaller) { \
                high = mid; \
            } \
            else { \
                low = mid + 1; \
            } \
        } \
        if (low == org_high) { \
            BSEARCH_CHECK(conv(low)); \
            if (!smaller) return Qnil; \
        } \
        return satisfied; \
    } while (0)


    beg = RANGE_BEG(range);
    end = RANGE_END(range);

    if (FIXNUM_P(beg) && FIXNUM_P(end)) {
        long low = FIX2LONG(beg);
        long high = FIX2LONG(end);
        long mid, org_high;
        BSEARCH(INT2FIX);
    }
#if SIZEOF_DOUBLE == 8 && defined(HAVE_INT64_T)
    else if (RB_TYPE_P(beg, T_FLOAT) || RB_TYPE_P(end, T_FLOAT)) {
        int64_t low  = double_as_int64(RFLOAT_VALUE(rb_Float(beg)));
        int64_t high = double_as_int64(RFLOAT_VALUE(rb_Float(end)));
        int64_t mid, org_high;
        BSEARCH(int64_as_double_to_num);
    }
#endif
    else if (is_integer_p(beg) && is_integer_p(end)) {
        VALUE low = rb_to_int(beg);
        VALUE high = rb_to_int(end);
        VALUE mid, org_high;
        RETURN_ENUMERATOR(range, 0, 0);
        if (EXCL(range)) high = rb_funcall(high, '-', 1, INT2FIX(1));
        org_high = high;

        while (rb_cmpint(rb_funcall(low, id_cmp, 1, high), low, high) < 0) {
            mid = rb_funcall(rb_funcall(high, '+', 1, low), id_div, 1, INT2FIX(2));
            BSEARCH_CHECK(mid);
            if (smaller) {
                high = mid;
            }
            else {
                low = rb_funcall(mid, '+', 1, INT2FIX(1));
            }
        }
        if (rb_equal(low, org_high)) {
            BSEARCH_CHECK(low);
            if (!smaller) return Qnil;
        }
        return satisfied;
    }
    else {
        rb_raise(rb_eTypeError, "can't do binary search for %s", rb_obj_classname(beg));
    }
    return range;
}

cover?(obj) → true or false click to toggle source

Returns true if obj is between the begin and end of the range.

This tests begin <= obj <= end when exclude_end? is false and begin <= obj < end when exclude_end? is true.

("a".."z").cover?("c")    #=> true
("a".."z").cover?("5")    #=> false
("a".."z").cover?("cc")   #=> true

 
               static VALUE
range_cover(VALUE range, VALUE val)
{
    VALUE beg, end;

    beg = RANGE_BEG(range);
    end = RANGE_END(range);
    return r_cover_p(range, beg, end, val);
}

each {| i | block } → rng click to toggle source

each → an_enumerator

Iterates over the elements of range, passing each in turn to the block.

The each method can only be used if the begin object of the range supports the succ method. A TypeError is raised if the object does not have succ method defined (like Float).

If no block is given, an enumerator is returned instead.

(10..15).each {|n| print n, ' ' }
# prints: 10 11 12 13 14 15

(2.5..5).each {|n| print n, ' ' }
# raises: TypeError: can't iterate from Float

 
               static VALUE
range_each(VALUE range)
{
    VALUE beg, end;

    RETURN_SIZED_ENUMERATOR(range, 0, 0, range_enum_size);

    beg = RANGE_BEG(range);
    end = RANGE_END(range);

    if (FIXNUM_P(beg) && FIXNUM_P(end)) { /* fixnums are special */
        long lim = FIX2LONG(end);
        long i;

        if (!EXCL(range))
            lim += 1;
        for (i = FIX2LONG(beg); i < lim; i++) {
            rb_yield(LONG2FIX(i));
        }
    }
    else if (SYMBOL_P(beg) && SYMBOL_P(end)) { /* symbols are special */
        VALUE args[2];

        args[0] = rb_sym2str(end);
        args[1] = EXCL(range) ? Qtrue : Qfalse;
        rb_block_call(rb_sym2str(beg), rb_intern("upto"), 2, args, sym_each_i, 0);
    }
    else {
        VALUE tmp = rb_check_string_type(beg);

        if (!NIL_P(tmp)) {
            VALUE args[2];

            args[0] = end;
            args[1] = EXCL(range) ? Qtrue : Qfalse;
            rb_block_call(tmp, rb_intern("upto"), 2, args, each_i, 0);
        }
        else {
            if (!discrete_object_p(beg)) {
                rb_raise(rb_eTypeError, "can't iterate from %s",
                         rb_obj_classname(beg));
            }
            range_each_func(range, each_i, 0);
        }
    }
    return range;
}

end → obj click to toggle source

Returns the object that defines the end of the range.

(1..10).end    #=> 10
(1...10).end   #=> 10

 
               static VALUE
range_end(VALUE range)
{
    return RANGE_END(range);
}

eql?(obj) → true or false click to toggle source

Returns true only if obj is a Range, has equivalent begin and end items (by comparing them with eql?), and has the same exclude_end? setting as the range.

(0..2).eql?(0..2)            #=> true
(0..2).eql?(Range.new(0,2))  #=> true
(0..2).eql?(0...2)           #=> false

 
               static VALUE
range_eql(VALUE range, VALUE obj)
{
    if (range == obj)
        return Qtrue;
    if (!rb_obj_is_kind_of(obj, rb_cRange))
        return Qfalse;
    return rb_exec_recursive_paired(recursive_eql, range, obj, obj);
}

exclude_end? → true or false click to toggle source

Returns true if the range excludes its end value.

(1..5).exclude_end?     #=> false
(1...5).exclude_end?    #=> true

 
               static VALUE
range_exclude_end_p(VALUE range)
{
    return EXCL(range) ? Qtrue : Qfalse;
}

first → obj click to toggle source

first(n) → an_array

Returns the first object in the range, or an array of the first n elements.

(10..20).first     #=> 10
(10..20).first(3)  #=> [10, 11, 12]

 
               static VALUE
range_first(int argc, VALUE *argv, VALUE range)
{
    VALUE n, ary[2];

    if (argc == 0) return RANGE_BEG(range);

    rb_scan_args(argc, argv, "1", &n);
    ary[0] = n;
    ary[1] = rb_ary_new2(NUM2LONG(n));
    rb_block_call(range, idEach, 0, 0, first_i, (VALUE)ary);

    return ary[1];
}

hash → integer click to toggle source

Compute a hash-code for this range. Two ranges with equal begin and end points (using eql?), and the same exclude_end? value will generate the same hash-code.

See also Object#hash.

 
               static VALUE
range_hash(VALUE range)
{
    st_index_t hash = EXCL(range);
    VALUE v;

    hash = rb_hash_start(hash);
    v = rb_hash(RANGE_BEG(range));
    hash = rb_hash_uint(hash, NUM2LONG(v));
    v = rb_hash(RANGE_END(range));
    hash = rb_hash_uint(hash, NUM2LONG(v));
    hash = rb_hash_uint(hash, EXCL(range) << 24);
    hash = rb_hash_end(hash);

    return LONG2FIX(hash);
}

include?(obj) → true or false click to toggle source

Returns true if obj is an element of the range, false otherwise. If begin and end are numeric, comparison is done according to the magnitude of the values.

("a".."z").include?("g")   #=> true
("a".."z").include?("A")   #=> false
("a".."z").include?("cc")  #=> false

 
               static VALUE
range_include(VALUE range, VALUE val)
{
    VALUE beg = RANGE_BEG(range);
    VALUE end = RANGE_END(range);
    int nv = FIXNUM_P(beg) || FIXNUM_P(end) ||
             linear_object_p(beg) || linear_object_p(end);

    if (nv ||
        !NIL_P(rb_check_to_integer(beg, "to_int")) ||
        !NIL_P(rb_check_to_integer(end, "to_int"))) {
        return r_cover_p(range, beg, end, val);
    }
    else if (RB_TYPE_P(beg, T_STRING) && RB_TYPE_P(end, T_STRING)) {
        VALUE rb_str_include_range_p(VALUE beg, VALUE end, VALUE val, VALUE exclusive);
        return rb_str_include_range_p(beg, end, val, RANGE_EXCL(range));
    }
    /* TODO: ruby_frame->this_func = rb_intern("include?"); */
    return rb_call_super(1, &val);
}

inspect → string click to toggle source

Convert this range object to a printable form (using inspect to convert the begin and end objects).

 
               static VALUE
range_inspect(VALUE range)
{
    return rb_exec_recursive(inspect_range, range, 0);
}

last → obj click to toggle source

last(n) → an_array

Returns the last object in the range, or an array of the last n elements.

Note that with no arguments last will return the object that defines the end of the range even if exclude_end? is true.

(10..20).last      #=> 20
(10...20).last     #=> 20
(10..20).last(3)   #=> [18, 19, 20]
(10...20).last(3)  #=> [17, 18, 19]

 
               static VALUE
range_last(int argc, VALUE *argv, VALUE range)
{
    if (argc == 0) return RANGE_END(range);
    return rb_ary_last(argc, argv, rb_Array(range));
}

max → obj click to toggle source

max {| a,b | block } → obj

max(n) → obj

max(n) {| a,b | block } → obj

Returns the maximum value in the range. Returns nil if the begin value of the range larger than the end value. Returns nil if the begin value of an exclusive range is equal to the end value.

Can be given an optional block to override the default comparison method a <=> b.

(10..20).max    #=> 20

 
               static VALUE
range_max(int argc, VALUE *argv, VALUE range)
{
    VALUE e = RANGE_END(range);
    int nm = FIXNUM_P(e) || rb_obj_is_kind_of(e, rb_cNumeric);

    if (rb_block_given_p() || (EXCL(range) && !nm) || argc) {
        return rb_call_super(argc, argv);
    }
    else {
        struct cmp_opt_data cmp_opt = { 0, 0 };
        VALUE b = RANGE_BEG(range);
        int c = OPTIMIZED_CMP(b, e, cmp_opt);

        if (c > 0)
            return Qnil;
        if (EXCL(range)) {
            if (!FIXNUM_P(e) && !rb_obj_is_kind_of(e, rb_cInteger)) {
                rb_raise(rb_eTypeError, "cannot exclude non Integer end value");
            }
            if (c == 0) return Qnil;
            if (!FIXNUM_P(b) && !rb_obj_is_kind_of(b,rb_cInteger)) {
                rb_raise(rb_eTypeError, "cannot exclude end value with non Integer begin value");
            }
            if (FIXNUM_P(e)) {
                return LONG2NUM(FIX2LONG(e) - 1);
            }
            return rb_funcall(e, '-', 1, INT2FIX(1));
        }
        return e;
    }
}

member?(obj) → true or false click to toggle source

Returns true if obj is an element of the range, false otherwise. If begin and end are numeric, comparison is done according to the magnitude of the values.

("a".."z").include?("g")   #=> true
("a".."z").include?("A")   #=> false
("a".."z").include?("cc")  #=> false

 
               static VALUE
range_include(VALUE range, VALUE val)
{
    VALUE beg = RANGE_BEG(range);
    VALUE end = RANGE_END(range);
    int nv = FIXNUM_P(beg) || FIXNUM_P(end) ||
             linear_object_p(beg) || linear_object_p(end);

    if (nv ||
        !NIL_P(rb_check_to_integer(beg, "to_int")) ||
        !NIL_P(rb_check_to_integer(end, "to_int"))) {
        return r_cover_p(range, beg, end, val);
    }
    else if (RB_TYPE_P(beg, T_STRING) && RB_TYPE_P(end, T_STRING)) {
        VALUE rb_str_include_range_p(VALUE beg, VALUE end, VALUE val, VALUE exclusive);
        return rb_str_include_range_p(beg, end, val, RANGE_EXCL(range));
    }
    /* TODO: ruby_frame->this_func = rb_intern("include?"); */
    return rb_call_super(1, &val);
}

min → obj click to toggle source

min {| a,b | block } → obj

min(n) → array

min(n) {| a,b | block } → array

Returns the minimum value in the range. Returns nil if the begin value of the range is larger than the end value. Returns nil if the begin value of an exclusive range is equal to the end value.

Can be given an optional block to override the default comparison method a <=> b.

(10..20).min    #=> 10

 
               static VALUE
range_min(int argc, VALUE *argv, VALUE range)
{
    if (rb_block_given_p()) {
        return rb_call_super(argc, argv);
    }
    else if (argc != 0) {
        return range_first(argc, argv, range);
    }
    else {
        struct cmp_opt_data cmp_opt = { 0, 0 };
        VALUE b = RANGE_BEG(range);
        VALUE e = RANGE_END(range);
        int c = OPTIMIZED_CMP(b, e, cmp_opt);

        if (c > 0 || (c == 0 && EXCL(range)))
            return Qnil;
        return b;
    }
}

size → num click to toggle source

Returns the number of elements in the range. Both the begin and the end of the Range must be Numeric, otherwise nil is returned.

(10..20).size    #=> 11
('a'..'z').size  #=> nil
(-Float::INFINITY..Float::INFINITY).size #=> Infinity

 
               static VALUE
range_size(VALUE range)
{
    VALUE b = RANGE_BEG(range), e = RANGE_END(range);
    if (rb_obj_is_kind_of(b, rb_cNumeric) && rb_obj_is_kind_of(e, rb_cNumeric)) {
        return ruby_num_interval_step_size(b, e, INT2FIX(1), EXCL(range));
    }
    return Qnil;
}

step(n=1) {| obj | block } → rng click to toggle source

step(n=1) → an_enumerator

Iterates over the range, passing each nth element to the block. If begin and end are numeric, n is added for each iteration. Otherwise step invokes succ to iterate through range elements.

If no block is given, an enumerator is returned instead.

range = Xs.new(1)..Xs.new(10)
range.step(2) {|x| puts x}
puts
range.step(3) {|x| puts x}

produces:

 1 x
 3 xxx
 5 xxxxx
 7 xxxxxxx
 9 xxxxxxxxx

 1 x
 4 xxxx
 7 xxxxxxx
10 xxxxxxxxxx

See Range for the definition of class Xs.

 
               static VALUE
range_step(int argc, VALUE *argv, VALUE range)
{
    VALUE b, e, step, tmp;

    RETURN_SIZED_ENUMERATOR(range, argc, argv, range_step_size);

    b = RANGE_BEG(range);
    e = RANGE_END(range);
    if (argc == 0) {
        step = INT2FIX(1);
    }
    else {
        rb_scan_args(argc, argv, "01", &step);
        step = check_step_domain(step);
    }

    if (FIXNUM_P(b) && FIXNUM_P(e) && FIXNUM_P(step)) { /* fixnums are special */
        long end = FIX2LONG(e);
        long i, unit = FIX2LONG(step);

        if (!EXCL(range))
            end += 1;
        i = FIX2LONG(b);
        while (i < end) {
            rb_yield(LONG2NUM(i));
            if (i + unit < i) break;
            i += unit;
        }

    }
    else if (SYMBOL_P(b) && SYMBOL_P(e)) { /* symbols are special */
        VALUE args[2], iter[2];

        args[0] = rb_sym2str(e);
        args[1] = EXCL(range) ? Qtrue : Qfalse;
        iter[0] = INT2FIX(1);
        iter[1] = step;
        rb_block_call(rb_sym2str(b), rb_intern("upto"), 2, args, sym_step_i, (VALUE)iter);
    }
    else if (ruby_float_step(b, e, step, EXCL(range))) {
        /* done */
    }
    else if (rb_obj_is_kind_of(b, rb_cNumeric) ||
             !NIL_P(rb_check_to_integer(b, "to_int")) ||
             !NIL_P(rb_check_to_integer(e, "to_int"))) {
        ID op = EXCL(range) ? '<' : idLE;
        VALUE v = b;
        int i = 0;

        while (RTEST(rb_funcall(v, op, 1, e))) {
            rb_yield(v);
            i++;
            v = rb_funcall(b, '+', 1, rb_funcall(INT2NUM(i), '*', 1, step));
        }
    }
    else {
        tmp = rb_check_string_type(b);

        if (!NIL_P(tmp)) {
            VALUE args[2], iter[2];

            b = tmp;
            args[0] = e;
            args[1] = EXCL(range) ? Qtrue : Qfalse;
            iter[0] = INT2FIX(1);
            iter[1] = step;
            rb_block_call(b, rb_intern("upto"), 2, args, step_i, (VALUE)iter);
        }
        else {
            VALUE args[2];

            if (!discrete_object_p(b)) {
                rb_raise(rb_eTypeError, "can't iterate from %s",
                         rb_obj_classname(b));
            }
            args[0] = INT2FIX(1);
            args[1] = step;
            range_each_func(range, step_i, (VALUE)args);
        }
    }
    return range;
}

to_s → string click to toggle source

Convert this range object to a printable form (using to_s to convert the begin and end objects).

 
               static VALUE
range_to_s(VALUE range)
{
    VALUE str, str2;

    str = rb_obj_as_string(RANGE_BEG(range));
    str2 = rb_obj_as_string(RANGE_END(range));
    str = rb_str_dup(str);
    rb_str_cat(str, "...", EXCL(range) ? 3 : 2);
    rb_str_append(str, str2);
    OBJ_INFECT(str, range);

    return str;
}