# class 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"]

## Endless Ranges¶ ↑

An “endless range” represents a semi-infinite range. Literal notation for an endless range is:

    (1..)
    # or similarly
    (1...)

Which is equivalent to

    (1..nil)  # or similarly (1...nil)
    Range.new(1, nil) # or Range.new(1, nil, true)

Endless ranges are useful, for example, for idiomatic slicing of arrays:

    [1, 2, 3, 4, 5][2...]   # => [3, 4, 5]

Some implementation details:

- `end` of endless range is `nil`;

- `each` of endless range enumerates infinite sequence (may be useful in combination with `Enumerable#take_while` or similar methods);

- `(1..)` and `(1...)` are not equal, although technically representing the same sequence.

## 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

json_create(object) click to toggle source

Deserializes `JSON` string by constructing new `Range` object with arguments `a` serialized by `to_json`.

    # File ext/json/lib/json/add/range.rb, line 10
    def self.json_create(object)
      new(*object['a'])
    end

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 range 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

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

Iterates over the range, passing each `n`th 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. Especially, the enumerator is an `Enumerator::ArithmeticSequence` if begin and end of the range are numeric.

    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_percent_step(VALUE range, VALUE step)
    {
        return range_step(1, &step, range);
    }

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)
    {
        VALUE ret = range_include_internal(range, val);
        if (ret != Qundef) return ret;
        return r_cover_p(range, RANGE_BEG(range), RANGE_END(range), val);
    }

as_json(*) click to toggle source

Returns a hash, that will be turned into a `JSON` object and represent this object.

    # File ext/json/lib/json/add/range.rb, line 16
    def as_json(*)
      {
        JSON.create_id  => self.class.name,
        'a'             => [ first, last, exclude_end? ]
      }
    end

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(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(NIL_P(end) ? HUGE_VAL : 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)) {
            RETURN_ENUMERATOR(range, 0, 0);
            return bsearch_integer_range(beg, end, EXCL(range));
        }
        else if (is_integer_p(beg) && NIL_P(end)) {
            VALUE diff = LONG2FIX(1);
            RETURN_ENUMERATOR(range, 0, 0);
            while (1) {
                VALUE mid = rb_funcall(beg, '+', 1, diff);
                BSEARCH_CHECK(mid);
                if (smaller) {
                    return bsearch_integer_range(beg, mid, 0);
                }
                diff = rb_funcall(diff, '*', 1, LONG2FIX(2));
            }
        }
        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
cover?(range) → true or false

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`.

If called with a `Range` argument, returns `true` when the given range is covered by the receiver, by comparing the begin and end values. If the argument can be treated as a sequence, this method treats it that way. In the specific case of `(a..b).cover?(c...d)` with `a <= c && b < d`, the end of the sequence must be calculated, which may exhibit poor performance if `c` is non-numeric. Returns `false` if the begin value of the range is larger than the end value.

    ("a".."z").cover?("c")  #=> true
    ("a".."z").cover?("5")  #=> false
    ("a".."z").cover?("cc") #=> true
    (1..5).cover?(2..3)     #=> true
    (1..5).cover?(0..6)     #=> false
    (1..5).cover?(1...6)    #=> true

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

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

        if (rb_obj_is_kind_of(val, rb_cRange)) {
            return RBOOL(r_cover_range_p(range, beg, end, val));
        }
        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;
        long i, lim;

        RETURN_SIZED_ENUMERATOR(range, 0, 0, range_enum_size);

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

        if (FIXNUM_P(beg) && NIL_P(end)) {
          fixnum_endless:
            i = FIX2LONG(beg);
            while (FIXABLE(i)) {
                rb_yield(LONG2FIX(i++));
            }
            beg = LONG2NUM(i);
          bignum_endless:
            for (;; beg = rb_big_plus(beg, INT2FIX(1)))
                rb_yield(beg);
        }
        else if (FIXNUM_P(beg) && FIXNUM_P(end)) { /* fixnums are special */
          fixnum_loop:
            lim = FIX2LONG(end);
            if (!EXCL(range))
                lim += 1;
            for (i = FIX2LONG(beg); i < lim; i++) {
                rb_yield(LONG2FIX(i));
            }
        }
        else if (RB_INTEGER_TYPE_P(beg) && (NIL_P(end) || RB_INTEGER_TYPE_P(end))) {
            if (SPECIAL_CONST_P(end) || RBIGNUM_POSITIVE_P(end)) { /* end >= FIXNUM_MIN */
                if (!FIXNUM_P(beg)) {
                    if (RBIGNUM_NEGATIVE_P(beg)) {
                        do {
                            rb_yield(beg);
                        } while (!FIXNUM_P(beg = rb_big_plus(beg, INT2FIX(1))));
                        if (NIL_P(end)) goto fixnum_endless;
                        if (FIXNUM_P(end)) goto fixnum_loop;
                    }
                    else {
                        if (NIL_P(end)) goto bignum_endless;
                        if (FIXNUM_P(end)) return range;
                    }
                }
                if (FIXNUM_P(beg)) {
                    i = FIX2LONG(beg);
                    do {
                        rb_yield(LONG2FIX(i));
                    } while (POSFIXABLE(++i));
                    beg = LONG2NUM(i);
                }
                ASSUME(!FIXNUM_P(beg));
                ASSUME(!SPECIAL_CONST_P(end));
            }
            if (!FIXNUM_P(beg) && RBIGNUM_SIGN(beg) == RBIGNUM_SIGN(end)) {
                if (EXCL(range)) {
                    while (rb_big_cmp(beg, end) == INT2FIX(-1)) {
                        rb_yield(beg);
                        beg = rb_big_plus(beg, INT2FIX(1));
                    }
                }
                else {
                    VALUE c;
                    while ((c = rb_big_cmp(beg, end)) != INT2FIX(1)) {
                        rb_yield(beg);
                        if (c == INT2FIX(0)) break;
                        beg = rb_big_plus(beg, INT2FIX(1));
                    }
                }
            }
        }
        else if (SYMBOL_P(beg) && (NIL_P(end) || SYMBOL_P(end))) { /* symbols are special */
            beg = rb_sym2str(beg);
            if (NIL_P(end)) {
                rb_str_upto_endless_each(beg, sym_each_i, 0);
            }
            else {
                rb_str_upto_each(beg, rb_sym2str(end), EXCL(range), sym_each_i, 0);
            }
        }
        else {
            VALUE tmp = rb_check_string_type(beg);

            if (!NIL_P(tmp)) {
                if (!NIL_P(end)) {
                    rb_str_upto_each(tmp, end, EXCL(range), each_i, 0);
                }
                else {
                    rb_str_upto_endless_each(tmp, each_i, 0);
                }
            }
            else {
                if (!discrete_object_p(beg)) {
                    rb_raise(rb_eTypeError, "can't iterate from %s",
                             rb_obj_classname(beg));
                }
                if (!NIL_P(end))
                    range_each_func(range, each_i, 0);
                else
                    for (;; beg = rb_funcallv(beg, id_succ, 0, 0))
                        rb_yield(beg);
            }
        }
        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);
    }

entries → array click to toggle source

Returns an array containing the items in the range.

    (1..7).to_a  #=> [1, 2, 3, 4, 5, 6, 7]
    (1..).to_a   #=> RangeError: cannot convert endless range to an array

    static VALUE
    range_to_a(VALUE range)
    {
        if (NIL_P(RANGE_END(range))) {
            rb_raise(rb_eRangeError, "cannot convert endless range to an array");
        }
        return rb_call_super(0, 0);
    }

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 ST2FIX(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 ret = range_include_internal(range, val);
        if (ret != Qundef) return ret;
        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 (NIL_P(RANGE_END(range))) {
            rb_raise(rb_eRangeError, "cannot get the last element of endless 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 (NIL_P(RANGE_END(range))) {
            rb_raise(rb_eRangeError, "cannot get the maximum of endless range");
        }

        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 (!RB_INTEGER_TYPE_P(e)) {
                    rb_raise(rb_eTypeError, "cannot exclude non Integer end value");
                }
                if (c == 0) return Qnil;
                if (!RB_INTEGER_TYPE_P(b)) {
                    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 ret = range_include_internal(range, val);
        if (ret != Qundef) return ret;
        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()) {
            if (NIL_P(RANGE_END(range))) {
                rb_raise(rb_eRangeError, "cannot get the minimum of endless range with custom comparison method");
            }
            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 = NIL_P(e) ? -1 : 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)) {
            if (rb_obj_is_kind_of(e, rb_cNumeric)) {
                return ruby_num_interval_step_size(b, e, INT2FIX(1), EXCL(range));
            }
            if (NIL_P(e)) {
                return DBL2NUM(HUGE_VAL);
            }
        }

        return Qnil;
    }

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

Iterates over the range, passing each `n`th 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. Especially, the enumerator is an `Enumerator::ArithmeticSequence` if begin and end of the range are numeric.

    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;

        b = RANGE_BEG(range);
        e = RANGE_END(range);
        step = (!rb_check_arity(argc, 0, 1) ? INT2FIX(1) : argv[0]);

        if (!rb_block_given_p()) {
            if (rb_obj_is_kind_of(b, rb_cNumeric) && (NIL_P(e) || rb_obj_is_kind_of(e, rb_cNumeric))) {
                return rb_arith_seq_new(range, ID2SYM(rb_frame_this_func()), argc, argv,
                        range_step_size, b, e, step, EXCL(range));
            }

            RETURN_SIZED_ENUMERATOR(range, argc, argv, range_step_size);
        }

        step = check_step_domain(step);

        if (FIXNUM_P(b) && NIL_P(e) && FIXNUM_P(step)) {
            long i = FIX2LONG(b), unit = FIX2LONG(step);
            do {
                rb_yield(LONG2FIX(i));
                i += unit;          /* FIXABLE+FIXABLE never overflow */
            } while (FIXABLE(i));
            b = LONG2NUM(i);

            for (;; b = rb_big_plus(b, step))
                rb_yield(b);
        }
        else 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) && (NIL_P(e) || SYMBOL_P(e))) { /* symbols are special */
            VALUE iter[2];
            iter[0] = INT2FIX(1);
            iter[1] = step;

            b = rb_sym2str(b);
            if (NIL_P(e)) {
                rb_str_upto_endless_each(b, sym_step_i, (VALUE)iter);
            }
            else {
                rb_str_upto_each(b, rb_sym2str(e), EXCL(range), sym_step_i, (VALUE)iter);
            }
        }
        else if (ruby_float_step(b, e, step, EXCL(range), TRUE)) {
            /* 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 (NIL_P(e) || 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 iter[2];

                b = tmp;
                iter[0] = INT2FIX(1);
                iter[1] = step;

                if (NIL_P(e)) {
                    rb_str_upto_endless_each(b, step_i, (VALUE)iter);
                }
                else {
                    rb_str_upto_each(b, e, EXCL(range), 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_a → array click to toggle source

Returns an array containing the items in the range.

    (1..7).to_a  #=> [1, 2, 3, 4, 5, 6, 7]
    (1..).to_a   #=> RangeError: cannot convert endless range to an array

    static VALUE
    range_to_a(VALUE range)
    {
        if (NIL_P(RANGE_END(range))) {
            rb_raise(rb_eRangeError, "cannot convert endless range to an array");
        }
        return rb_call_super(0, 0);
    }

to_json(*args) click to toggle source

Stores class name (Range) with `JSON` array of arguments `a` which include `first` (integer), `last` (integer), and `exclude_end?` (boolean) as `JSON` string.

    # File ext/json/lib/json/add/range.rb, line 26
    def to_json(*args)
      as_json.to_json(*args)
    end

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;
    }