Ruby

struct slicebetween_arg {

VALUE pat1;

VALUE pat2;

VALUE pred;

VALUE prev_elt;

VALUE prev_elts;

VALUE yielder;

};

static VALUE

slicebetween_ii(RB_BLOCK_CALL_FUNC_ARGLIST(i, _memo))

{

#define UPDATE_MEMO ((memo = MEMO_FOR(struct slicebetween_arg, _memo)), 1)

struct slicebetween_arg *memo;

int split_p;

UPDATE_MEMO;

ENUM_WANT_SVALUE();

if (NIL_P(memo->prev_elts)) {

/* The first element */

memo->prev_elt = i;

memo->prev_elts = rb_ary_new3(1, i);

}

else {

if (NIL_P(memo->pred)) {

split_p = RTEST(rb_funcall(memo->pat1, id_eqq, 1, memo->prev_elt));

UPDATE_MEMO;

if (split_p) {

split_p = RTEST(rb_funcall(memo->pat2, id_eqq, 1, i));

UPDATE_MEMO;

}

}

else {

split_p = RTEST(rb_funcall(memo->pred, id_call, 2, memo->prev_elt, i));

UPDATE_MEMO;

}

if (split_p) {

rb_funcall(memo->yielder, id_lshift, 1, memo->prev_elts);

UPDATE_MEMO;

memo->prev_elts = rb_ary_new3(1, i);

}

else {

rb_ary_push(memo->prev_elts, i);

}

memo->prev_elt = i;

}

return Qnil;

#undef UPDATE_MEMO

}

static VALUE

slicebetween_i(RB_BLOCK_CALL_FUNC_ARGLIST(yielder, enumerator))

{

VALUE enumerable;

VALUE arg;

struct slicebetween_arg *memo = NEW_MEMO_FOR(struct slicebetween_arg, arg);

enumerable = rb_ivar_get(enumerator, rb_intern("slicebetween_enum"));

memo->pat1 = rb_ivar_get(enumerator, rb_intern("slicebetween_pat1"));

memo->pat2 = rb_ivar_get(enumerator, rb_intern("slicebetween_pat2"));

memo->pred = rb_attr_get(enumerator, rb_intern("slicebetween_pred"));

memo->prev_elt = Qnil;

memo->prev_elts = Qnil;

memo->yielder = yielder;

rb_block_call(enumerable, id_each, 0, 0, slicebetween_ii, arg);

memo = MEMO_FOR(struct slicebetween_arg, arg);

if (!NIL_P(memo->prev_elts))

rb_funcall(memo->yielder, id_lshift, 1, memo->prev_elts);

return Qnil;

}

/*

* call-seq:

* enum.slice_between(pattern_before, pattern_after) -> an_enumerator

* enum.slice_between {|elt_before, elt_after| bool } -> an_enumerator

*

* Creates an enumerator for each chunked elements.

* The beginnings of chunks are defined by _pattern_before_ and _pattern_after_, or the block.

*

* This method split each chunk using adjacent elements, _elt_before_ and _elt_after_,

* in the receiver enumerator.

* If the patterns are given,

* this method split chunks between _elt_before_ and _elt_after_ where

* <code>_pattern_before_ === _elt_before_</code> and

* <code>_pattern_after_ === _elt_after_</code>.

* If the block is given,

* this method split chunks between _elt_before_ and _elt_after_ where

* the block returns true.

*

* For each split opportunity, _pattern_before_ test follows _pattern_after_ test.

* If _pattern_before_ is failed, _pattern_after_ is not tested.

*

* _pattern_before_ is not tested for the last element.

* _pattern_after_ is not tested for the first element.

* The block is called the length of the receiver enumerator minus one.

*

* The result enumerator yields the chunked elements as an array.

* So +each+ method can be called as follows:

*

* enum.slice_between(pattern_before, pattern_after).each { |ary| ... }

* enum.slice_between { |elt_before, elt_after| bool }.each { |ary| ... }

*

* Other methods of the Enumerator class and Enumerable module,

* such as +map+, etc., are also usable.

*

* For example, one-by-one increasing subsequence can be chunked as follows:

*

* a = [1,2,4,9,10,11,12,15,16,19,20,21]

* b = a.slice_between {|i, j| i+1 != j }

* p b.to_a #=> [[1, 2], [4], [9, 10, 11, 12], [15, 16], [19, 20, 21]]

* c = b.map {|a| a.length < 3 ? a : "#{a.first}-#{a.last}" }

* p c #=> [[1, 2], [4], "9-12", [15, 16], "19-21"]

* d = c.join(",")

* p d #=> "1,2,4,9-12,15,16,19-21"

*

* Increasing subsequence can be chunked as follows:

*

* a = [0, 9, 2, 2, 3, 2, 7, 5, 9, 5]

* p a.slice_between {|i, j| i > j }.to_a

* #=> [[0, 9], [2, 2, 3], [2, 7], [5, 9], [5]]

*

* Adjacent evens and odds can be chunked as follows:

* (Enumerable#chunk is another way to do it.)

*

* a = [7, 5, 9, 2, 0, 7, 9, 4, 2, 0]

* p a.slice_between {|i, j| i.even? != j.even? }.to_a

* #=> [[7, 5, 9], [2, 0], [7, 9], [4, 2, 0]]

*

* Paragraphs (non-empty lines with trailing empty lines) can be chunked as follows:

* (See Enumerable#chunk to ignore empty lines.)

*

* lines = ["foo\n", "bar\n", "\n", "baz\n", "qux\n"]

* p lines.slice_between(/\A\s*\z/, /\S/).to_a

* #=> [["foo\n", "bar\n", "\n"], ["baz\n", "qux\n"]]

*

* Mbox contains series of mails which start with Unix From line and end

* with an empty line.

* So each mail can be extracted by slice after an empty line before Unix From line.

*

* # split mails in mbox (slice before Unix From line after an empty line)

* open("mbox") { |f|

* f.slice_between("\n", /\AFrom /).each { |mail|

* mail.pop if mail.last == "\n"

* pp mail

* }

* }

*

*/

static VALUE

enum_slice_between(int argc, VALUE *argv, VALUE enumerable)

{

VALUE enumerator;

VALUE pat1 = Qnil, pat2 = Qnil, pred = Qnil;

if (rb_block_given_p()) {

pred = rb_block_proc();

if (0 < argc)

rb_raise(rb_eArgError, "both pattan and block are given");

}

else {

rb_scan_args(argc, argv, "2", &pat1, &pat2);

}

enumerator = rb_obj_alloc(rb_cEnumerator);

rb_ivar_set(enumerator, rb_intern("slicebetween_enum"), enumerable);

rb_ivar_set(enumerator, rb_intern("slicebetween_pat1"), pat1);

rb_ivar_set(enumerator, rb_intern("slicebetween_pat2"), pat2);

rb_ivar_set(enumerator, rb_intern("slicebetween_pred"), pred);

rb_block_call(enumerator, idInitialize, 0, 0, slicebetween_i, enumerator);

return enumerator;

}

rb_define_method(rb_mEnumerable, "slice_between", enum_slice_between, -1);

rb_define_method(rb_cLazy, "slice_between", lazy_super, -1);

def test_slice_between1

e = [].slice_between {|a, b| flunk "should not be called" }

assert_equal([], e.to_a)

e = [1,2].slice_between {|a,b| true }

assert_equal([[1], [2]], e.to_a)

e = [1,2].slice_between {|a,b| false }

assert_equal([[1, 2]], e.to_a)

end

def test_slice_between2

e = [1,2].slice_between(1, 2)

assert_equal([[1], [2]], e.to_a)

e = [1,2].slice_between(3, 2)

assert_equal([[1, 2]], e.to_a)

e = [1,2].slice_between(1, 3)

assert_equal([[1, 2]], e.to_a)

end

def test_slice_between_argerror

assert_raise(ArgumentError) { [].slice_between }

assert_raise(ArgumentError) { [].slice_between(1) }

assert_raise(ArgumentError) { [].slice_between(1) {|a, b| true } }

assert_raise(ArgumentError) { [].slice_between(1, 2) {|a, b| true } }

assert_raise(ArgumentError) { [].slice_between(nil, 2) {|a, b| true } }

end

def test_slice_between_contiguously_increasing_integers

e = [1,4,9,10,11,12,15,16,19,20,21].slice_between {|i, j| i+1 != j }

assert_equal([[1], [4], [9,10,11,12], [15,16], [19,20,21]], e.to_a)

end

def test_slice_between_mails

mail1 = ["From foo\n",

"\n",

"Body start\n",

"From x to b, baz\n",

"Body end\n",

"\n"]

mail2 = ["From foo\n",

"\n",

"Body start\n",

"Another text\n",

"Body end\n",

"\n"]

e = (mail1 + mail2).slice_between("\n", /\AFrom /)

assert_equal([mail1, mail2], e.to_a)

end

slice_between: [//, //],