In Files

  • enum.c
  • enumerator.c

Enumerable

The Enumerable mixin provides collection classes with several traversal and searching methods, and with the ability to sort. The class must provide a method each, which yields successive members of the collection. If Enumerable#max, #min, or #sort is used, the objects in the collection must also implement a meaningful <=> operator, as these methods rely on an ordering between members of the collection.

Public Instance Methods

all? [{|obj| block } ] => true or false click to toggle source

Passes each element of the collection to the given block. The method returns true if the block never returns false or nil. If the block is not given, Ruby adds an implicit block of {|obj| obj} (that is all? will return true only if none of the collection members are false or nil.)

%w{ant bear cat}.all? {|word| word.length >= 3}   #=> true
%w{ant bear cat}.all? {|word| word.length >= 4}   #=> false
[ nil, true, 99 ].all?                            #=> false

 
               static VALUE
enum_all(VALUE obj)
{
    VALUE result = Qtrue;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? all_iter_i : all_i, (VALUE)&result);
    return result;
}
any? [{|obj| block } ] => true or false click to toggle source

Passes each element of the collection to the given block. The method returns true if the block ever returns a value other than false or nil. If the block is not given, Ruby adds an implicit block of {|obj| obj} (that is any? will return true if at least one of the collection members is not false or nil.

%w{ant bear cat}.any? {|word| word.length >= 3}   #=> true
%w{ant bear cat}.any? {|word| word.length >= 4}   #=> true
[ nil, true, 99 ].any?                            #=> true

 
               static VALUE
enum_any(VALUE obj)
{
    VALUE result = Qfalse;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? any_iter_i : any_i, (VALUE)&result);
    return result;
}
collect {| obj | block } => array click to toggle source

Returns a new array with the results of running block once for every element in enum.

(1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
(1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]

 
               static VALUE
enum_collect(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);

    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, collect_i, ary);

    return ary;
}
count => int click to toggle source
count(item) => int
count {| obj | block } => int

Returns the number of items in enum, where size is called if it responds to it, otherwise the items are counted through enumeration. If an argument is given, counts the number of items in enum, for which equals to item. If a block is given, counts the number of elements yielding a true value.

ary = [1, 2, 4, 2]
ary.count             # => 4
ary.count(2)          # => 2
ary.count{|x|x%2==0}  # => 3

 
               static VALUE
enum_count(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo[2];      /* [count, condition value] */
    rb_block_call_func *func;

    if (argc == 0) {
        if (rb_block_given_p()) {
            func = count_iter_i;
        }
        else {
            if (rb_respond_to(obj, id_size)) {
                return rb_funcall(obj, id_size, 0, 0);
            }
            func = count_all_i;
        }
    }
    else {
        rb_scan_args(argc, argv, "1", &memo[1]);
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        func = count_i;
    }

    memo[0] = 0;
    rb_block_call(obj, id_each, 0, 0, func, (VALUE)&memo);
    return INT2NUM(memo[0]);
}
cycle {|obj| block } click to toggle source
cycle(n) {|obj| block }

Calls block for each element of enum repeatedly n times or forever if none or nil is given. If a non-positive number is given or the collection is empty, does nothing. Returns nil if the loop has finished without getting interrupted.

#cycle saves elements in an internal array so changes to enum after the first pass have no effect.

a = ["a", "b", "c"]
a.cycle {|x| puts x }  # print, a, b, c, a, b, c,.. forever.
a.cycle(2) {|x| puts x }  # print, a, b, c, a, b, c.

 
               static VALUE
enum_cycle(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary;
    VALUE nv = Qnil;
    long n, i, len;

    rb_scan_args(argc, argv, "01", &nv);

    RETURN_ENUMERATOR(obj, argc, argv);
    if (NIL_P(nv)) {
        n = -1;
    }
    else {
        n = NUM2LONG(nv);
        if (n <= 0) return Qnil;
    }
    ary = rb_ary_new();
    RBASIC(ary)->klass = 0;
    rb_block_call(obj, id_each, 0, 0, cycle_i, ary);
    len = RARRAY_LEN(ary);
    if (len == 0) return Qnil;
    while (n < 0 || 0 < --n) {
        for (i=0; i<len; i++) {
            rb_yield(RARRAY_PTR(ary)[i]);
        }
    }
    return Qnil;                /* not reached */
}
detect(ifnone = nil) {| obj | block } => obj or nil click to toggle source

Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or returns nil

(1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

 
               static VALUE
enum_find(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo = Qundef;
    VALUE if_none;

    rb_scan_args(argc, argv, "01", &if_none);
    RETURN_ENUMERATOR(obj, argc, argv);
    rb_block_call(obj, id_each, 0, 0, find_i, (VALUE)&memo);
    if (memo != Qundef) {
        return memo;
    }
    if (!NIL_P(if_none)) {
        return rb_funcall(if_none, rb_intern("call"), 0, 0);
    }
    return Qnil;
}
drop(n) => array click to toggle source

Drops first n elements from enum, and returns rest elements in an array.

a = [1, 2, 3, 4, 5, 0]
a.drop(3)             # => [4, 5, 0]

 
               static VALUE
enum_drop(VALUE obj, VALUE n)
{
    VALUE args[2];
    long len = NUM2LONG(n);

    if (len < 0) {
        rb_raise(rb_eArgError, "attempt to drop negative size");
    }

    args[1] = len;
    args[0] = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, drop_i, (VALUE)args);
    return args[0];
}
drop_while {|arr| block } => array click to toggle source

Drops elements up to, but not including, the first element for which the block returns nil or false and returns an array containing the remaining elements.

a = [1, 2, 3, 4, 5, 0]
a.drop_while {|i| i < 3 }   # => [3, 4, 5, 0]

 
               static VALUE
enum_drop_while(VALUE obj)
{
    VALUE args[2];

    RETURN_ENUMERATOR(obj, 0, 0);
    args[0] = rb_ary_new();
    args[1] = Qfalse;
    rb_block_call(obj, id_each, 0, 0, drop_while_i, (VALUE)args);
    return args[0];
}
each_cons(n) {...} click to toggle source
each_cons(n)

Iterates the given block for each array of consecutive <n> elements. If no block is given, returns an enumerator.

e.g.:

(1..10).each_cons(3) {|a| p a}
# outputs below
[1, 2, 3]
[2, 3, 4]
[3, 4, 5]
[4, 5, 6]
[5, 6, 7]
[6, 7, 8]
[7, 8, 9]
[8, 9, 10]

 
               static VALUE
enum_each_cons(VALUE obj, VALUE n)
{
    long size = NUM2LONG(n);
    VALUE args[2];

    if (size <= 0) rb_raise(rb_eArgError, "invalid size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_cons_i, (VALUE)args);

    return Qnil;
}
each_slice(n) {...} click to toggle source
each_slice(n)

Iterates the given block for each slice of <n> elements. If no block is given, returns an enumerator.

e.g.:

(1..10).each_slice(3) {|a| p a}
# outputs below
[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
[10]

 
               static VALUE
enum_each_slice(VALUE obj, VALUE n)
{
    long size = NUM2LONG(n);
    VALUE args[2], ary;

    if (size <= 0) rb_raise(rb_eArgError, "invalid slice size");
    RETURN_ENUMERATOR(obj, 1, &n);
    args[0] = rb_ary_new2(size);
    args[1] = (VALUE)size;

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_slice_i, (VALUE)args);

    ary = args[0];
    if (RARRAY_LEN(ary) > 0) rb_yield(ary);

    return Qnil;
}
each_with_index {|obj, i| block } → enum click to toggle source

Calls block with two arguments, the item and its index, for each item in enum. Given arguments are passed through to each().

hash = Hash.new
%w(cat dog wombat).each_with_index {|item, index|
  hash[item] = index
}
hash   #=> {"cat"=>0, "dog"=>1, "wombat"=>2}

 
               static VALUE
enum_each_with_index(int argc, VALUE *argv, VALUE obj)
{
    long memo;

    RETURN_ENUMERATOR(obj, argc, argv);

    memo = 0;
    rb_block_call(obj, id_each, argc, argv, each_with_index_i, (VALUE)&memo);
    return obj;
}
each_with_object(obj) {|(*args), memo_obj| ... } click to toggle source
each_with_object(obj)

Iterates the given block for each element with an arbitrary object given, and returns the initially given object.

If no block is given, returns an enumerator.

e.g.:

evens = (1..10).each_with_object([]) {|i, a| a << i*2 }
# => [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]

 
               static VALUE
enum_each_with_object(VALUE obj, VALUE memo)
{
    RETURN_ENUMERATOR(obj, 1, &memo);

    rb_block_call(obj, SYM2ID(sym_each), 0, 0, each_with_object_i, memo);

    return memo;
}
entries => array click to toggle source

Returns an array containing the items in enum.

(1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
{ 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]

 
               static VALUE
enum_to_a(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary = rb_ary_new();

    rb_block_call(obj, id_each, argc, argv, collect_all, ary);
    OBJ_INFECT(ary, obj);

    return ary;
}
find(ifnone = nil) {| obj | block } => obj or nil click to toggle source

Passes each entry in enum to block. Returns the first for which block is not false. If no object matches, calls ifnone and returns its result when it is specified, or returns nil

(1..10).detect  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).detect {|i| i % 5 == 0 and i % 7 == 0 }   #=> 35

 
               static VALUE
enum_find(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo = Qundef;
    VALUE if_none;

    rb_scan_args(argc, argv, "01", &if_none);
    RETURN_ENUMERATOR(obj, argc, argv);
    rb_block_call(obj, id_each, 0, 0, find_i, (VALUE)&memo);
    if (memo != Qundef) {
        return memo;
    }
    if (!NIL_P(if_none)) {
        return rb_funcall(if_none, rb_intern("call"), 0, 0);
    }
    return Qnil;
}
find_all {| obj | block } => array click to toggle source

Returns an array containing all elements of enum for which block is not false (see also Enumerable#reject).

(1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]

 
               static VALUE
enum_find_all(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);

    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, find_all_i, ary);

    return ary;
}
find_index(value) => int or nil click to toggle source
find_index {| obj | block } => int or nil

Compares each entry in enum with value or passes to block. Returns the index for the first for which the evaluated value is non-false. If no object matches, returns nil

(1..10).find_index  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
(1..100).find_index {|i| i % 5 == 0 and i % 7 == 0 }   #=> 34
(1..100).find_index(50)                                #=> 49

 
               static VALUE
enum_find_index(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo[3];      /* [return value, current index, condition value] */
    rb_block_call_func *func;

    if (argc == 0) {
        RETURN_ENUMERATOR(obj, 0, 0);
        func = find_index_iter_i;
    }
    else {
        rb_scan_args(argc, argv, "1", &memo[2]);
        if (rb_block_given_p()) {
            rb_warn("given block not used");
        }
        func = find_index_i;
    }

    memo[0] = Qnil;
    memo[1] = 0;
    rb_block_call(obj, id_each, 0, 0, func, (VALUE)memo);
    return memo[0];
}
first → obj or nil click to toggle source
first(n) → an_array

Returns the first element, or the first n elements, of the enumerable. If the enumerable is empty, the first form returns nil, and the second form returns an empty array.

 
               static VALUE
enum_first(int argc, VALUE *argv, VALUE obj)
{
    VALUE n, params[2];

    if (argc == 0) {
        params[0] = params[1] = Qnil;
    }
    else {
        long len;

        rb_scan_args(argc, argv, "01", &n);
        len = NUM2LONG(n);
        if (len == 0) return rb_ary_new2(0);
        params[0] = len;
        params[1] = rb_ary_new2(len);
    }
    rb_block_call(obj, id_each, 0, 0, first_i, (VALUE)params);

    return params[1];
}
grep(pattern) => array click to toggle source
grep(pattern) {| obj | block } => array

Returns an array of every element in enum for which Pattern === element. If the optional block is supplied, each matching element is passed to it, and the block's result is stored in the output array.

(1..100).grep 38..44   #=> [38, 39, 40, 41, 42, 43, 44]
c = IO.constants
c.grep(/SEEK/)         #=> [:SEEK_SET, :SEEK_CUR, :SEEK_END]
res = c.grep(/SEEK/) {|v| IO.const_get(v) }
res                    #=> [0, 1, 2]

 
               static VALUE
enum_grep(VALUE obj, VALUE pat)
{
    VALUE ary = rb_ary_new();
    VALUE arg[2];

    arg[0] = pat;
    arg[1] = ary;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? grep_iter_i : grep_i, (VALUE)arg);

    return ary;
}
group_by {| obj | block } => a_hash click to toggle source

Returns a hash, which keys are evaluated result from the block, and values are arrays of elements in enum corresponding to the key.

(1..6).group_by {|i| i%3}   #=> {0=>[3, 6], 1=>[1, 4], 2=>[2, 5]}

 
               static VALUE
enum_group_by(VALUE obj)
{
    VALUE hash;

    RETURN_ENUMERATOR(obj, 0, 0);

    hash = rb_hash_new();
    rb_block_call(obj, id_each, 0, 0, group_by_i, hash);
    OBJ_INFECT(hash, obj);

    return hash;
}
include?(obj) => true or false click to toggle source

Returns true if any member of enum equals obj. Equality is tested using ==.

IO.constants.include? :SEEK_SET          #=> true
IO.constants.include? :SEEK_NO_FURTHER   #=> false

 
               static VALUE
enum_member(VALUE obj, VALUE val)
{
    VALUE memo[2];

    memo[0] = val;
    memo[1] = Qfalse;
    rb_block_call(obj, id_each, 0, 0, member_i, (VALUE)memo);
    return memo[1];
}
inject(initial, sym) => obj click to toggle source
inject(sym) => obj
inject(initial) {| memo, obj | block } => obj
inject {| memo, obj | block } => obj

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.

If you specify a block, then for each element in enum<i> the block is passed an accumulator value (<i>memo) and the element. If you specify a symbol instead, then each element in the collection will be passed to the named method of memo. In either case, the result becomes the new value for memo. At the end of the iteration, the final value of memo is the return value fo the method.

If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo.

Examples:

# Sum some numbers
(5..10).reduce(:+)                            #=> 45
# Same using a block and inject
(5..10).inject {|sum, n| sum + n }            #=> 45
# Multiply some numbers
(5..10).reduce(1, :*)                         #=> 151200
# Same using a block
(5..10).inject(1) {|product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
   memo.length > word.length ? memo : word
end
longest                                       #=> "sheep"

 
               static VALUE
enum_inject(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo[2];
    VALUE (*iter)(VALUE, VALUE, int, VALUE*) = inject_i;

    switch (rb_scan_args(argc, argv, "02", &memo[0], &memo[1])) {
      case 0:
        memo[0] = Qundef;
        break;
      case 1:
        if (rb_block_given_p()) {
            break;
        }
        memo[1] = (VALUE)rb_to_id(memo[0]);
        memo[0] = Qundef;
        iter = inject_op_i;
        break;
      case 2:
        if (rb_block_given_p()) {
            rb_warning("given block not used");
        }
        memo[1] = (VALUE)rb_to_id(memo[1]);
        iter = inject_op_i;
        break;
    }
    rb_block_call(obj, id_each, 0, 0, iter, (VALUE)memo);
    if (memo[0] == Qundef) return Qnil;
    return memo[0];
}
map {| obj | block } => array click to toggle source

Returns a new array with the results of running block once for every element in enum.

(1..4).collect {|i| i*i }   #=> [1, 4, 9, 16]
(1..4).collect { "cat"  }   #=> ["cat", "cat", "cat", "cat"]

 
               static VALUE
enum_collect(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);

    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, collect_i, ary);

    return ary;
}
max => obj click to toggle source
max {|a,b| block } => obj

Returns the object in enum with the maximum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.max                                  #=> "horse"
a.max {|a,b| a.length <=> b.length }   #=> "albatross"

 
               static VALUE
enum_max(VALUE obj)
{
    VALUE result[2];

    result[0] = Qundef;
    if (rb_block_given_p()) {
        result[1] = rb_ary_new3(2, Qnil, Qnil);
        rb_block_call(obj, id_each, 0, 0, max_ii, (VALUE)result);
    }
    else {
        rb_block_call(obj, id_each, 0, 0, max_i, (VALUE)result);
    }
    if (result[0] == Qundef) return Qnil;
    return result[0];
}
max_by {| obj| block } => obj click to toggle source

Returns the object in enum that gives the maximum value from the given block.

a = %w(albatross dog horse)
a.max_by {|x| x.length }   #=> "albatross"

 
               static VALUE
enum_max_by(VALUE obj)
{
    VALUE memo[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qnil;
    rb_block_call(obj, id_each, 0, 0, max_by_i, (VALUE)memo);
    return memo[1];
}
member?(obj) => true or false click to toggle source

Returns true if any member of enum equals obj. Equality is tested using ==.

IO.constants.include? :SEEK_SET          #=> true
IO.constants.include? :SEEK_NO_FURTHER   #=> false

 
               static VALUE
enum_member(VALUE obj, VALUE val)
{
    VALUE memo[2];

    memo[0] = val;
    memo[1] = Qfalse;
    rb_block_call(obj, id_each, 0, 0, member_i, (VALUE)memo);
    return memo[1];
}
min => obj click to toggle source
min {| a,b | block } => obj

Returns the object in enum with the minimum value. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.min                                  #=> "albatross"
a.min {|a,b| a.length <=> b.length }   #=> "dog"

 
               static VALUE
enum_min(VALUE obj)
{
    VALUE result[2];

    result[0] = Qundef;
    if (rb_block_given_p()) {
        result[1] = rb_ary_new3(2, Qnil, Qnil);
        rb_block_call(obj, id_each, 0, 0, min_ii, (VALUE)result);
    }
    else {
        rb_block_call(obj, id_each, 0, 0, min_i, (VALUE)result);
    }
    if (result[0] == Qundef) return Qnil;
    return result[0];
}
min_by {| obj| block } => obj click to toggle source

Returns the object in enum that gives the minimum value from the given block.

a = %w(albatross dog horse)
a.min_by {|x| x.length }   #=> "dog"

 
               static VALUE
enum_min_by(VALUE obj)
{
    VALUE memo[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qnil;
    rb_block_call(obj, id_each, 0, 0, min_by_i, (VALUE)memo);
    return memo[1];
}
minmax => [min,max] click to toggle source
minmax {|a,b| block } => [min,max]

Returns two elements array which contains the minimum and the maximum value in the enumerable. The first form assumes all objects implement Comparable; the second uses the block to return a <=> b.

a = %w(albatross dog horse)
a.minmax                                  #=> ["albatross", "horse"]
a.minmax {|a,b| a.length <=> b.length }   #=> ["dog", "albatross"]

 
               static VALUE
enum_minmax(VALUE obj)
{
    VALUE result[3];
    VALUE ary = rb_ary_new3(2, Qnil, Qnil);

    result[0] = Qundef;
    if (rb_block_given_p()) {
        result[2] = ary;
        rb_block_call(obj, id_each, 0, 0, minmax_ii, (VALUE)result);
    }
    else {
        rb_block_call(obj, id_each, 0, 0, minmax_i, (VALUE)result);
    }
    if (result[0] != Qundef) {
        RARRAY_PTR(ary)[0] = result[0];
        RARRAY_PTR(ary)[1] = result[1];
    }
    return ary;
}
minmax_by {| obj| block } => [min, max] click to toggle source

Returns two elements array array containing the objects in enum that gives the minimum and maximum values respectively from the given block.

a = %w(albatross dog horse)
a.minmax_by {|x| x.length }   #=> ["dog", "albatross"]

 
               static VALUE
enum_minmax_by(VALUE obj)
{
    VALUE memo[4];

    RETURN_ENUMERATOR(obj, 0, 0);

    memo[0] = Qundef;
    memo[1] = Qundef;
    memo[2] = Qnil;
    memo[3] = Qnil;
    rb_block_call(obj, id_each, 0, 0, minmax_by_i, (VALUE)memo);
    return rb_assoc_new(memo[2], memo[3]);
}
none? [{|obj| block }] => true or false click to toggle source

Passes each element of the collection to the given block. The method returns true if the block never returns true for all elements. If the block is not given, none? will return true only if none of the collection members is true.

%w{ant bear cat}.none? {|word| word.length == 5}  #=> true
%w{ant bear cat}.none? {|word| word.length >= 4}  #=> false
[].none?                                          #=> true
[nil].none?                                       #=> true
[nil,false].none?                                 #=> true

 
               static VALUE
enum_none(VALUE obj)
{
    VALUE result = Qtrue;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? none_iter_i : none_i, (VALUE)&result);
    return result;
}
one? [{|obj| block }] => true or false click to toggle source

Passes each element of the collection to the given block. The method returns true if the block returns true exactly once. If the block is not given, one? will return true only if exactly one of the collection members is true.

%w{ant bear cat}.one? {|word| word.length == 4}   #=> true
%w{ant bear cat}.one? {|word| word.length > 4}    #=> false
%w{ant bear cat}.one? {|word| word.length < 4}    #=> false
[ nil, true, 99 ].one?                            #=> false
[ nil, true, false ].one?                         #=> true

 
               static VALUE
enum_one(VALUE obj)
{
    VALUE result = Qundef;

    rb_block_call(obj, id_each, 0, 0, rb_block_given_p() ? one_iter_i : one_i, (VALUE)&result);
    if (result == Qundef) return Qfalse;
    return result;
}
partition {| obj | block } => [ true_array, false_array ] click to toggle source

Returns two arrays, the first containing the elements of enum for which the block evaluates to true, the second containing the rest.

(1..6).partition {|i| (i&1).zero?}   #=> [[2, 4, 6], [1, 3, 5]]

 
               static VALUE
enum_partition(VALUE obj)
{
    VALUE ary[2];

    RETURN_ENUMERATOR(obj, 0, 0);

    ary[0] = rb_ary_new();
    ary[1] = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, partition_i, (VALUE)ary);

    return rb_assoc_new(ary[0], ary[1]);
}
reduce(initial, sym) => obj click to toggle source
reduce(sym) => obj
reduce(initial) {| memo, obj | block } => obj
reduce {| memo, obj | block } => obj

Combines all elements of enum by applying a binary operation, specified by a block or a symbol that names a method or operator.

If you specify a block, then for each element in enum<i> the block is passed an accumulator value (<i>memo) and the element. If you specify a symbol instead, then each element in the collection will be passed to the named method of memo. In either case, the result becomes the new value for memo. At the end of the iteration, the final value of memo is the return value fo the method.

If you do not explicitly specify an initial value for memo, then uses the first element of collection is used as the initial value of memo.

Examples:

# Sum some numbers
(5..10).reduce(:+)                            #=> 45
# Same using a block and inject
(5..10).inject {|sum, n| sum + n }            #=> 45
# Multiply some numbers
(5..10).reduce(1, :*)                         #=> 151200
# Same using a block
(5..10).inject(1) {|product, n| product * n } #=> 151200
# find the longest word
longest = %w{ cat sheep bear }.inject do |memo,word|
   memo.length > word.length ? memo : word
end
longest                                       #=> "sheep"

 
               static VALUE
enum_inject(int argc, VALUE *argv, VALUE obj)
{
    VALUE memo[2];
    VALUE (*iter)(VALUE, VALUE, int, VALUE*) = inject_i;

    switch (rb_scan_args(argc, argv, "02", &memo[0], &memo[1])) {
      case 0:
        memo[0] = Qundef;
        break;
      case 1:
        if (rb_block_given_p()) {
            break;
        }
        memo[1] = (VALUE)rb_to_id(memo[0]);
        memo[0] = Qundef;
        iter = inject_op_i;
        break;
      case 2:
        if (rb_block_given_p()) {
            rb_warning("given block not used");
        }
        memo[1] = (VALUE)rb_to_id(memo[1]);
        iter = inject_op_i;
        break;
    }
    rb_block_call(obj, id_each, 0, 0, iter, (VALUE)memo);
    if (memo[0] == Qundef) return Qnil;
    return memo[0];
}
reject {| obj | block } => array click to toggle source

Returns an array for all elements of enum for which block is false (see also Enumerable#find_all).

(1..10).reject {|i|  i % 3 == 0 }   #=> [1, 2, 4, 5, 7, 8, 10]

 
               static VALUE
enum_reject(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);

    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, reject_i, ary);

    return ary;
}
reverse_each {|item| block } click to toggle source

Traverses enum in reverse order.

 
               static VALUE
enum_reverse_each(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary;
    long i;

    RETURN_ENUMERATOR(obj, argc, argv);

    ary = enum_to_a(argc, argv, obj);

    for (i = RARRAY_LEN(ary); --i >= 0; ) {
        rb_yield(RARRAY_PTR(ary)[i]);
    }

    return obj;
}
select {| obj | block } => array click to toggle source

Returns an array containing all elements of enum for which block is not false (see also Enumerable#reject).

(1..10).find_all {|i|  i % 3 == 0 }   #=> [3, 6, 9]

 
               static VALUE
enum_find_all(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);

    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, find_all_i, ary);

    return ary;
}
sort => array click to toggle source
sort {| a, b | block } => array

Returns an array containing the items in enum sorted, either according to their own <=> method, or by using the results of the supplied block. The block should return -1, 0, or +1 depending on the comparison between a and b. As of Ruby 1.8, the method Enumerable#sort_by implements a built-in Schwartzian Transform, useful when key computation or comparison is expensive..

%w(rhea kea flea).sort         #=> ["flea", "kea", "rhea"]
(1..10).sort {|a,b| b <=> a}   #=> [10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

 
               static VALUE
enum_sort(VALUE obj)
{
    return rb_ary_sort(enum_to_a(0, 0, obj));
}
sort_by {| obj | block } => array click to toggle source

Sorts enum using a set of keys generated by mapping the values in enum through the given block.

%w{ apple pear fig }.sort_by {|word| word.length}
              #=> ["fig", "pear", "apple"]

The current implementation of sort_by generates an array of tuples containing the original collection element and the mapped value. This makes sort_by fairly expensive when the keysets are simple

require 'benchmark'
include Benchmark

a = (1..100000).map {rand(100000)}

bm(10) do |b|
  b.report("Sort")    { a.sort }
  b.report("Sort by") { a.sort_by {|a| a} }
end

produces:

user     system      total        real
Sort        0.180000   0.000000   0.180000 (  0.175469)
Sort by     1.980000   0.040000   2.020000 (  2.013586)

However, consider the case where comparing the keys is a non-trivial operation. The following code sorts some files on modification time using the basic sort method.

files = Dir["*"]
sorted = files.sort {|a,b| File.new(a).mtime <=> File.new(b).mtime}
sorted   #=> ["mon", "tues", "wed", "thurs"]

This sort is inefficient: it generates two new File objects during every comparison. A slightly better technique is to use the Kernel#test method to generate the modification times directly.

files = Dir["*"]
sorted = files.sort { |a,b|
  test(?M, a) <=> test(?M, b)
}
sorted   #=> ["mon", "tues", "wed", "thurs"]

This still generates many unnecessary Time objects. A more efficient technique is to cache the sort keys (modification times in this case) before the sort. Perl users often call this approach a Schwartzian Transform, after Randal Schwartz. We construct a temporary array, where each element is an array containing our sort key along with the filename. We sort this array, and then extract the filename from the result.

sorted = Dir["*"].collect { |f|
   [test(?M, f), f]
}.sort.collect { |f| f[1] }
sorted   #=> ["mon", "tues", "wed", "thurs"]

This is exactly what sort_by does internally.

sorted = Dir["*"].sort_by {|f| test(?M, f)}
sorted   #=> ["mon", "tues", "wed", "thurs"]

 
               static VALUE
enum_sort_by(VALUE obj)
{
    VALUE ary;
    long i;

    RETURN_ENUMERATOR(obj, 0, 0);

    if (TYPE(obj) == T_ARRAY) {
        ary  = rb_ary_new2(RARRAY_LEN(obj));
    }
    else {
        ary = rb_ary_new();
    }
    RBASIC(ary)->klass = 0;
    rb_block_call(obj, id_each, 0, 0, sort_by_i, ary);
    if (RARRAY_LEN(ary) > 1) {
        ruby_qsort(RARRAY_PTR(ary), RARRAY_LEN(ary), sizeof(VALUE),
                   sort_by_cmp, (void *)ary);
    }
    if (RBASIC(ary)->klass) {
        rb_raise(rb_eRuntimeError, "sort_by reentered");
    }
    for (i=0; i<RARRAY_LEN(ary); i++) {
        RARRAY_PTR(ary)[i] = RNODE(RARRAY_PTR(ary)[i])->u2.value;
    }
    RBASIC(ary)->klass = rb_cArray;
    OBJ_INFECT(ary, obj);

    return ary;
}
take(n) => array click to toggle source

Returns first n elements from enum.

a = [1, 2, 3, 4, 5, 0]
a.take(3)             # => [1, 2, 3]

 
               static VALUE
enum_take(VALUE obj, VALUE n)
{
    VALUE args[2];
    long len = NUM2LONG(n);

    if (len < 0) {
        rb_raise(rb_eArgError, "attempt to take negative size");
    }

    if (len == 0) return rb_ary_new2(0);
    args[0] = rb_ary_new();
    args[1] = len;
    rb_block_call(obj, id_each, 0, 0, take_i, (VALUE)args);
    return args[0];
}
take_while {|arr| block } => array click to toggle source

Passes elements to the block until the block returns nil or false, then stops iterating and returns an array of all prior elements.

a = [1, 2, 3, 4, 5, 0]
a.take_while {|i| i < 3 }   # => [1, 2]

 
               static VALUE
enum_take_while(VALUE obj)
{
    VALUE ary;

    RETURN_ENUMERATOR(obj, 0, 0);
    ary = rb_ary_new();
    rb_block_call(obj, id_each, 0, 0, take_while_i, (VALUE)&ary);
    return ary;
}
to_a => array click to toggle source

Returns an array containing the items in enum.

(1..7).to_a                       #=> [1, 2, 3, 4, 5, 6, 7]
{ 'a'=>1, 'b'=>2, 'c'=>3 }.to_a   #=> [["a", 1], ["b", 2], ["c", 3]]

 
               static VALUE
enum_to_a(int argc, VALUE *argv, VALUE obj)
{
    VALUE ary = rb_ary_new();

    rb_block_call(obj, id_each, argc, argv, collect_all, ary);
    OBJ_INFECT(ary, obj);

    return ary;
}
zip(arg, ...) => enumerator click to toggle source
zip(arg, ...) {|arr| block } => nil

Takes one element from enum and merges corresponding elements from each args. This generates a sequence of n-element arrays, where n is one more than the count of arguments. The length of the resulting sequence will be enum#size</code. If the size of any argument is less than <code>enum#size, nil values are supplied. If a block is given, it is invoked for each output array, otherwise an array of arrays is returned.

a = [ 4, 5, 6 ]
b = [ 7, 8, 9 ]

[1,2,3].zip(a, b)      #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
[1,2].zip(a,b)         #=> [[1, 4, 7], [2, 5, 8]]
a.zip([1,2],[8])       #=> [[4, 1, 8], [5, 2, nil], [6, nil, nil]]

 
               static VALUE
enum_zip(int argc, VALUE *argv, VALUE obj)
{
    int i;
    ID conv;
    NODE *memo;
    VALUE result = Qnil;
    VALUE args = rb_ary_new4(argc, argv);
    int allary = Qtrue;

    argv = RARRAY_PTR(args);
    for (i=0; i<argc; i++) {
        VALUE ary = rb_check_array_type(argv[i]);
        if (NIL_P(ary)) {
            allary = Qfalse;
            break;
        }
        argv[i] = ary;
    }
    if (!allary) {
        CONST_ID(conv, "to_enum");
        for (i=0; i<argc; i++) {
            argv[i] = rb_funcall(argv[i], conv, 1, ID2SYM(id_each));
        }
    }
    if (!rb_block_given_p()) {
        result = rb_ary_new();
    }
    /* use NODE_DOT2 as memo(v, v, -) */
    memo = rb_node_newnode(NODE_DOT2, result, args, 0);
    rb_block_call(obj, id_each, 0, 0, allary ? zip_ary : zip_i, (VALUE)memo);

    return result;
}