Ruby

struct sliceafter_arg {

VALUE pat;

VALUE pred;

VALUE prev_elts;

VALUE yielder;

};

static VALUE

sliceafter_ii(RB_BLOCK_CALL_FUNC_ARGLIST(i, _memo))

{

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

struct sliceafter_arg *memo;

int split_p;

UPDATE_MEMO;

ENUM_WANT_SVALUE();

if (NIL_P(memo->prev_elts)) {

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

}

else {

rb_ary_push(memo->prev_elts, i);

}

if (NIL_P(memo->pred)) {

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

UPDATE_MEMO;

}

else {

split_p = RTEST(rb_funcall(memo->pred, id_call, 1, i));

UPDATE_MEMO;

}

if (split_p) {

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

UPDATE_MEMO;

memo->prev_elts = Qnil;

}

return Qnil;

#undef UPDATE_MEMO

}

static VALUE

sliceafter_i(RB_BLOCK_CALL_FUNC_ARGLIST(yielder, enumerator))

{

VALUE enumerable;

VALUE arg;

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

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

memo->pat = rb_ivar_get(enumerator, rb_intern("sliceafter_pat"));

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

memo->prev_elts = Qnil;

memo->yielder = yielder;

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

memo = MEMO_FOR(struct sliceafter_arg, arg);

if (!NIL_P(memo->prev_elts))

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

return Qnil;

}

/*

* call-seq:

* enum.slice_after(pattern) -> an_enumerator

* enum.slice_after { |elt| bool } -> an_enumerator

*

* Creates an enumerator for each chunked elements.

* The ends of chunks are defined by _pattern_ and the block.

*

* If <code>_pattern_ === _elt_</code> returns <code>true</code> or the block

* returns <code>true</code> for the element, the element is end of a

* chunk.

*

* The <code>===</code> and _block_ is called from the first element to the last

* element of _enum_.

*

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

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

*

* enum.slice_after(pattern).each { |ary| ... }

* enum.slice_after { |elt| bool }.each { |ary| ... }

*

* Other methods of the Enumerator class and Enumerable module,

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

*

* For example, continuation lines (lines end with backslash) can be

* concatenated as follows:

*

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

* e = lines.slice_after(/(?<!\\)\n\z/)

* p e.to_a

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

* p e.map {|ll| ll[0...-1].map {|l| l.sub(/\\\n\z/, "") }.join + ll.last }

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

*

*/

static VALUE

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

{

VALUE enumerator;

VALUE pat = Qnil, pred = Qnil;

if (rb_block_given_p()) {

if (0 < argc)

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

pred = rb_block_proc();

}

else {

rb_scan_args(argc, argv, "1", &pat);

}

enumerator = rb_obj_alloc(rb_cEnumerator);

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

rb_ivar_set(enumerator, rb_intern("sliceafter_pat"), pat);

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

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

return enumerator;

}

rb_define_method(rb_mEnumerable, "slice_after", enum_slice_after, -1);

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

def test_slice_after0

assert_raise(ArgumentError) { [].slice_after }

end

def test_slice_after1

e = [].slice_after {|a| flunk "should not be called" }

assert_equal([], e.to_a)

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

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

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

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

[true, false].each {|b|

block_results = [true, b]

e = [1,2].slice_after {|a| block_results.shift }

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

assert_equal([], block_results)

block_results = [false, b]

e = [1,2].slice_after {|a| block_results.shift }

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

assert_equal([], block_results)

}

end

def test_slice_after_both_pattern_and_block

assert_raise(ArgumentError) { [].slice_after(1) {|a| true } }

end

def test_slice_after_continuation_lines

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

e = lines.slice_after(/[^\\]\n\z/)

assert_equal([["foo\n"], ["bar\\\n", "baz\n"], ["\n", "qux\n"]], e.to_a)

end

def test_slice_before_empty_line

lines = ["foo", "", "bar"]

e = lines.slice_after(/\A\s*\z/)

assert_equal([["foo", ""], ["bar"]], e.to_a)

end

slice_after: //,