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Iterator.pm6
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Iterator.pm6
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# This class contains generally usable methods creating Iterators.
# There are two reasons for having this in a separate class:
#
# 1. Nice to have a separate file for similar stuff. Rakudo::Internals
# has become a hodgepodge of stuff of late.
# 2. Improve readability/searchability of code using these iterators, as
# many already have a long name, and having them prefixed with the more
# general Rakudo::Internals in the code, as opposed for the definite
# Rakudo::Iterator, feels better.
class Rakudo::Iterator {
my $empty := nqp::list; # an empty list for nqp::splice
#-------------------------------------------------------------------------------
# Roles that are used by iterators in the rest of the core settings, in
# alphabetical order for easier perusal.
# Generic role for iterating over a Blob / Buf. You need to
# supply at least a .pull-one. Takes a Blob / Buf as the only
# parameter to .new.
our role Blobby does PredictiveIterator {
has $!blob;
has Int $!i; # sadly, this can not be a native int yet :-(
method !SET-SELF(\blob) {
nqp::stmts( # something to iterator over
($!blob := blob),
($!i = -1),
self
)
}
method new(\blob) {
nqp::if(
nqp::isgt_i(nqp::elems(blob),0),
nqp::create(self)!SET-SELF(blob),
Rakudo::Iterator.Empty # nothing to iterate
)
}
# We can provide a generic push-all to the iterator as the
# result of a push-all is always immutable, so we can use
# the atpos_i here in both cases.
method push-all(\target --> IterationEnd) {
nqp::stmts(
(my $blob := $!blob), # attribute access is slower
(my int $elems = nqp::elems($blob)),
(my int $i = $!i),
nqp::while(
nqp::islt_i(($i = nqp::add_i($i,1)),$elems),
target.push(nqp::atpos_i($blob,$i))
),
($!i = $i)
)
}
method count-only(--> Int:D) {
nqp::p6box_i(
nqp::elems($!blob)
- $!i
- nqp::islt_i($!i,nqp::elems($!blob))
)
}
method sink-all(--> IterationEnd) { $!i = nqp::elems($!blob) }
}
# Generic role for iterating over a Map / Hash. You must
# at least provide your own .pull-one. Takes a Map / Hash
# as the only parameter to .new.
our role Mappy does Iterator {
has $!hash;
has $!iter;
method !SET-SELF(\hash) {
nqp::if(
($!hash := nqp::if(
nqp::istype(hash,Rakudo::Internals::IterationSet),
hash,
nqp::getattr(hash,Map,'$!storage')
)) && ($!iter := nqp::iterator($!hash)),
self,
Rakudo::Iterator.Empty # nothing to iterate
)
}
method new(\hash) { nqp::create(self)!SET-SELF(hash) }
method skip-one() { nqp::if($!iter,nqp::stmts(nqp::shift($!iter),1)) }
method sink-all(--> IterationEnd) { $!iter := nqp::null }
}
# Generic role for iterating over a Map / Hash that has pairs
# for values providing the "real" key and value. A default
# .pull-one and .push-all is provided. Takes a Map / Hash as
# the only parameter to .new.
our role Mappy-kv-from-pairs does Iterator {
has $!hash;
has $!iter;
has $!on;
method !SET-SELF(\hash) {
nqp::if(
($!hash := nqp::if(
nqp::istype(hash,Rakudo::Internals::IterationSet),
hash,
nqp::getattr(hash,Map,'$!storage')
)) && ($!iter := nqp::iterator($!hash)),
self,
Rakudo::Iterator.Empty # nothing to iterate
)
}
method new(\hash) { nqp::create(self)!SET-SELF(hash) }
method pull-one() is raw {
nqp::if(
$!on,
nqp::stmts(
($!on = 0),
nqp::getattr(nqp::iterval($!iter),Pair,'$!value')
),
nqp::if(
$!iter,
nqp::stmts(
($!on = 1),
nqp::getattr(nqp::iterval(nqp::shift($!iter)),Pair,'$!key')
),
IterationEnd
)
)
}
method push-all(\target --> IterationEnd) {
nqp::while(
$!iter,
nqp::stmts( # doesn't sink
(my $pair := nqp::decont(nqp::iterval(nqp::shift($!iter)))),
target.push(nqp::getattr($pair,Pair,'$!key')),
target.push(nqp::getattr($pair,Pair,'$!value'))
)
)
}
method skip-one() { # must define our own skip-one
nqp::if(
$!on,
nqp::not_i($!on = 0),
nqp::if(
$!iter,
nqp::stmts(
nqp::shift($!iter),
($!on = 1)
)
)
)
}
method sink-all(--> IterationEnd) { $!iter := nqp::null }
}
# Generic role for iterating over a >1 dimensional shaped list
# for its lowest branches. The default .new method takes a List
# to iterate over. A consuming class needs to provide a .process
# method, which will be called with each iteration with the
# $!indices attribute set to the coordinates of the branch being
# iterated for this time (with the highest element index set to 0).
# Consuming class can optionally provide a .done method that will
# be called just before the iterator returns IterationEnd.
our role ShapeBranch does Iterator {
has $!dims;
has $!indices;
has Mu $!list;
has int $!maxdim;
has int $!maxind;
has int $!level;
# Every time process() gets called, the following attributes are set:
# $!indices a list_i with current position, with the highest elem 0
# $!level level at which exhaustion happened
# $!dims a list_i with dimensions
# $!maxdim maximum element number in $!dims
# $!maxind maximum element number in lowest level list
method process { ... } # consumer needs to supply a .process
method done(--> Nil) { } # by default no action at end
method dims() { # HLL version of $!dims
nqp::stmts(
(my $buffer :=
nqp::setelems(nqp::create(IterationBuffer),nqp::elems($!dims))),
(my int $i = -1),
nqp::while( # convert list_i to list
nqp::isle_i(($i = nqp::add_i($i,1)),$!maxdim),
nqp::bindpos($buffer,$i,nqp::atpos_i($!dims,$i))
),
$buffer.List
)
}
method !SET-SELF(Mu \list) {
nqp::stmts(
nqp::if(
nqp::istype(list,List),
nqp::stmts( # List like
($!list := nqp::getattr(list,List,'$!reified')),
(my $shape := list.shape),
(my int $dims = $shape.elems), # reifies
($!dims := nqp::setelems(nqp::list_i,$dims)),
(my int $i = -1),
nqp::while(
nqp::islt_i(($i = nqp::add_i($i,1)),$dims),
nqp::bindpos_i($!dims,$i,
nqp::atpos(nqp::getattr($shape,List,'$!reified'),$i))
)
),
($dims = nqp::elems($!dims := nqp::dimensions($!list := list)))
),
($!indices := nqp::setelems(nqp::list_i,$dims)),
($!maxdim = nqp::sub_i($dims,1)),
($!maxind = nqp::sub_i(nqp::atpos_i($!dims,$!maxdim),1)),
self
)
}
method new(Mu \list) { nqp::create(self)!SET-SELF(list) }
method pull-one() is raw {
nqp::if(
nqp::isge_i($!level,0),
nqp::stmts( # still iterating
(my $result := self.process), # do the processing
(my int $level = $!maxdim),
nqp::until( # update indices
nqp::islt_i( # exhausted ??
($level = nqp::sub_i($level,1)),0) # next level
|| nqp::stmts(
nqp::bindpos_i($!indices,nqp::add_i($level,1),0), # reset
nqp::islt_i(
nqp::bindpos_i($!indices,$level, # increment this level
nqp::add_i(nqp::atpos_i($!indices,$level),1)),
nqp::atpos_i($!dims,$level) # out of range?
),
),
nqp::null
),
($!level = $level), # set level for next call
$result # what we found
),
nqp::stmts(
nqp::if(
nqp::iseq_i($!level,-1),
nqp::stmts( # first time telling we're done
self.done, # notify we're done
($!level = -2) # do this only once
)
),
IterationEnd # done iterating
)
)
}
}
# Generic role for iterating over a >1 dimensional shaped list
# for its values (leaves). The default .new method takes a List
# to iterate over. A consuming class needs to provide a .result
# method, which will be called with each iteration with the
# $!indices attribute set to the coordinates of the element being
# iterated for this time. In some cases, the iterator is iterated
# over for the side-effects in .result only. Which is why this
# role supplies an optimized .sink-all.
our role ShapeLeaf does Iterator {
has $!dims;
has $!indices;
has Mu $!list;
has int $!maxdim;
has int $!max;
# Every time .result gets called, the following attributes are set:
# $!indices a list_i with current coordinate
# $!dims a list_i with dimensions
# $!maxdim maximum element number in $!dims
method result { ... } # consumer needs to supply a .result
method indices() { # HLL version of $!indices
nqp::stmts(
(my $result := nqp::setelems(nqp::list,nqp::elems($!indices))),
(my int $i = -1),
nqp::while( # convert list_i to list
nqp::isle_i(($i = nqp::add_i($i,1)),$!maxdim),
nqp::bindpos($result,$i,nqp::atpos_i($!indices,$i))
),
$result
)
}
method !SET-SELF(Mu \list) {
nqp::stmts(
nqp::if(
nqp::istype(list,List),
nqp::stmts( # List like
($!list := nqp::getattr(list,List,'$!reified')),
(my $shape := list.shape),
(my int $dims = $shape.elems), # reifies
($!dims := nqp::setelems(nqp::list_i,$dims)),
(my int $i = -1),
nqp::while(
nqp::islt_i(($i = nqp::add_i($i,1)),$dims),
nqp::bindpos_i($!dims,$i,
nqp::atpos(nqp::getattr($shape,List,'$!reified'),$i))
)
),
($dims = nqp::elems($!dims := nqp::dimensions($!list := list)))
),
($!indices := nqp::setelems(nqp::list_i,$dims)),
($!maxdim = nqp::sub_i($dims,1)),
($!max = nqp::atpos_i($!dims,$!maxdim)),
self
)
}
method new(Mu \list) { nqp::create(self)!SET-SELF(list) }
method pull-one() is raw {
nqp::if(
$!indices,
nqp::stmts( # still iterating
(my $result := self.result), # process
nqp::if(
nqp::islt_i(
(my int $i =
nqp::add_i(nqp::atpos_i($!indices,$!maxdim),1)),
$!max
),
nqp::bindpos_i($!indices,$!maxdim,$i), # ready for next
nqp::stmts( # done for now
(my int $level = $!maxdim),
nqp::until( # update indices
nqp::islt_i( # exhausted ??
($level = nqp::sub_i($level,1)),0)
|| nqp::stmts(
nqp::bindpos_i($!indices,nqp::add_i($level,1),0),
nqp::islt_i(
nqp::bindpos_i($!indices,$level,
nqp::add_i(nqp::atpos_i($!indices,$level),1)),
nqp::atpos_i($!dims,$level)
),
),
nqp::null
),
nqp::if(
nqp::islt_i($level,0),
$!indices := nqp::null # done next time
)
)
),
$result # what we found
),
IterationEnd # done now
)
}
method push-all(\target --> IterationEnd) {
nqp::while(
$!indices,
nqp::stmts( # still iterating
(my int $i = nqp::atpos_i($!indices,$!maxdim)),
nqp::while(
nqp::isle_i(($i = nqp::add_i($i,1)),$!max),
nqp::stmts(
target.push(self.result), # process
nqp::bindpos_i($!indices,$!maxdim,$i), # ready for next
)
),
(my int $level = $!maxdim), # done for now
nqp::until( # update indices
nqp::islt_i( # exhausted ??
($level = nqp::sub_i($level,1)),0)
|| nqp::stmts(
nqp::bindpos_i($!indices,nqp::add_i($level,1),0),
nqp::islt_i(
nqp::bindpos_i($!indices,$level,
nqp::add_i(nqp::atpos_i($!indices,$level),1)),
nqp::atpos_i($!dims,$level)
),
),
nqp::null
),
nqp::if(
nqp::islt_i($level,0),
$!indices := nqp::null # done
)
)
)
}
method sink-all(--> IterationEnd) {
nqp::while(
$!indices,
nqp::stmts( # still iterating
(my int $i = nqp::atpos_i($!indices,$!maxdim)),
nqp::while(
nqp::isle_i(($i = nqp::add_i($i,1)),$!max),
nqp::stmts(
self.result, # process
nqp::bindpos_i($!indices,$!maxdim,$i), # ready for next
)
),
(my int $level = $!maxdim), # done for now
nqp::until( # update indices
nqp::islt_i( # exhausted ??
($level = nqp::sub_i($level,1)),0)
|| nqp::stmts(
nqp::bindpos_i($!indices,nqp::add_i($level,1),0),
nqp::islt_i(
nqp::bindpos_i($!indices,$level,
nqp::add_i(nqp::atpos_i($!indices,$level),1)),
nqp::atpos_i($!dims,$level)
),
),
nqp::null
),
nqp::if(
nqp::islt_i($level,0),
$!indices := nqp::null # done
)
)
)
}
}
#-------------------------------------------------------------------------------
# Methods that generate an Iterator (in alphabetical order)
# Create iterator that produces all values *except* the last N values
# of a given iterator. Returns an empty iterator if the given iterator
# produced fewer than N values.
my class AllButLastNValues does Iterator {
has $!iterator;
has $!buffered;
has int $!size;
has int $!index;
method !SET-SELF(\iterator, int $size) {
nqp::stmts(
(my int $i = -1),
(my \buffered := nqp::setelems(nqp::list,$size)),
nqp::while( # fill buffer to produce from
nqp::islt_i(($i = nqp::add_i($i,1)),$size)
&& nqp::not_i(nqp::eqaddr(
(my \pulled := iterator.pull-one),
IterationEnd
)),
nqp::bindpos(buffered,$i,pulled)
),
nqp::if(
nqp::islt_i($i,$size),
Rakudo::Iterator.Empty, # didn't produce enough
nqp::stmts( # we're in business
($!iterator := iterator),
($!buffered := buffered),
($!size = $size),
self
)
)
)
}
method new(\iterator,\n) {
nqp::if(
nqp::isle_i(n,0),
iterator, # we wants it all
nqp::create(self)!SET-SELF(iterator,n)
)
}
method pull-one() is raw {
nqp::if(
nqp::eqaddr((my \pulled := $!iterator.pull-one),IterationEnd),
pulled, # we're done
nqp::stmts( # produce/update buffer
(my \value := nqp::atpos($!buffered,$!index)),
nqp::bindpos($!buffered,$!index,pulled),
($!index = nqp::mod_i(nqp::add_i($!index,1),$!size)),
value
)
)
}
}
method AllButLastNValues(\iterator, \n) {
AllButLastNValues.new(iterator,n)
}
# Return an iterator that will generate a pair with the value as the
# key and as value the key of the given iterator, basically the
# .antipairs functionality on 1 dimensional lists.
my class AntiPair does Iterator {
has Mu $!iter;
has int $!key;
method !SET-SELF(\iter) { $!iter := iter; $!key = -1; self }
method new(\iter) { nqp::create(self)!SET-SELF(iter) }
method pull-one() is raw {
nqp::if(
nqp::eqaddr((my \pulled := $!iter.pull-one),IterationEnd),
IterationEnd,
Pair.new(pulled,+($!key = nqp::add_i($!key,1)))
)
}
method push-all(\target --> IterationEnd) {
my int $key = -1;
nqp::until(
nqp::eqaddr((my \pulled := $!iter.pull-one),IterationEnd),
target.push(Pair.new(pulled,+($key = nqp::add_i($key,1))))
)
}
method is-lazy() { $!iter.is-lazy }
}
method AntiPair(\iterator) { AntiPair.new(iterator) }
# Return an iterator that takes an Associative and an Iterable that
# generates keys, to call the AT-KEY method on the Associative.
my class AssociativeIterableKeys does Iterator {
has $!associative;
has $!iterator;
method !SET-SELF($!associative,$!iterator) { self }
method new(\asso,\iter) { nqp::create(self)!SET-SELF(asso,iter) }
method pull-one() is raw {
nqp::if(
nqp::eqaddr((my \key := $!iterator.pull-one),IterationEnd),
IterationEnd,
$!associative.AT-KEY(key)
)
}
method push-all(\target --> IterationEnd) {
my \iterator := $!iterator;
my \associative := $!associative;
nqp::until(
nqp::eqaddr((my \key := iterator.pull-one),IterationEnd),
target.push(associative.AT-KEY(key))
)
}
}
method AssociativeIterableKeys(\asso, \iterable) {
AssociativeIterableKeys.new(asso,iterable.iterator)
}
# Return an iterator that batches the given source iterator in
# batches of the given size. The third parameter indicates whether
# a partial batch should be returned when the source iterator has
# exhausted. The returned iterator is as lazy as the source iterator.
my class Batch does Iterator {
has $!iterator;
has int $!size;
has int $!complete;
has int $!is-exhausted;
method !SET-SELF(\iterator,\size,\partial) {
nqp::stmts(
($!iterator := iterator),
nqp::if(
nqp::istype(size,Whatever),
($!size = -1), # set to never stop and ok partial
nqp::if(
size < 1,
X::OutOfRange.new(
what => "Batching sublist length is",
got => size,
range => "1..^Inf",
).throw,
nqp::if(
(nqp::istype(size,Int)
&& nqp::isbig_I(nqp::decont(size)))
|| size == Inf,
($!size = -1), # set to never stop and ok partial
nqp::stmts(
($!size = size),
($!complete = !partial),
)
)
)
),
self
)
}
method new(\it,\si,\pa) { nqp::create(self)!SET-SELF(it,si,pa) }
method pull-one() is raw {
nqp::if(
$!is-exhausted,
IterationEnd,
nqp::stmts(
(my \reified := nqp::create(IterationBuffer)),
nqp::until(
nqp::iseq_i(nqp::elems(reified),$!size)
|| nqp::eqaddr(
(my \pulled := $!iterator.pull-one),
IterationEnd
),
nqp::push(reified,pulled)
),
nqp::if(
nqp::eqaddr(pulled,IterationEnd)
&& ($!is-exhausted = 1) # set the flag
&& ($!complete || nqp::not_i(nqp::elems(reified))),
IterationEnd,
reified.List
)
)
)
}
method is-lazy() { $!iterator.is-lazy }
}
method Batch(\iterator,\size,\partial) { Batch.new(iterator,size,partial) }
# Return an iterator for a given Callable. The Callable is supposed
# to return a value for the iterator, or IterationEnd to indicate the
# data from the Callable is exhausted. No checks for Slips are done,
# so they will be passed on as is. Also optionally takes a flag to
# mark the iterator as lazy or not: default is False (not lazy)
proto method Callable(|) {*}
my class CallableEager does Iterator {
has &!callable;
method new(&callable) {
nqp::p6bindattrinvres(
nqp::create(self),self,'&!callable',&callable)
}
method pull-one() is raw { &!callable() }
}
multi method Callable(&callable) { CallableEager.new(&callable) }
my class CallableLazy does Iterator {
has &!callable;
method new(&callable) {
nqp::p6bindattrinvres(
nqp::create(self),self,'&!callable',&callable)
}
method pull-one() is raw { &!callable() }
method is-lazy(--> True) { }
}
multi method Callable(&callable, Bool() $lazy) {
$lazy
?? CallableLazy.new(&callable)
!! CallableEager.new(&callable)
}
# Return an iterator for the "thunk xx 42" functionality.
my class Callable-xx-Times does Iterator {
has @!slipped;
has $!code;
has $!times;
method !SET-SELF(\code,\times) {
nqp::stmts(
($!code := code),
($!times = times),
self
)
}
method new(\code,\times) {
nqp::if(
times > 0,
nqp::create(self)!SET-SELF(code,times),
Rakudo::Iterator.Empty
)
}
method pull-one() {
nqp::if(
@!slipped,
@!slipped.shift,
nqp::if(
$!times > 0,
nqp::stmts(
--$!times, # consumed a value
nqp::if(
nqp::istype((my \pulled := $!code()),Slip),
nqp::if(
(@!slipped = pulled),
@!slipped.shift,
IterationEnd
),
nqp::if(
nqp::istype(pulled,Seq),
pulled.cache,
pulled
)
)
),
IterationEnd
)
)
}
}
method Callable-xx-Times(&code, Int:D \times) {
Callable-xx-Times.new(&code,times)
}
# Return an iterator for the "thunk xx *" functionality.
my class Callable-xx-Whatever does Iterator {
has @!slipped;
has $!code;
method new(\code) {
nqp::p6bindattrinvres(nqp::create(self),self,'$!code',code)
}
method pull-one() {
nqp::if(
@!slipped,
@!slipped.shift,
nqp::if(
nqp::istype((my \pulled := $!code()),Slip),
nqp::if(
(@!slipped = pulled),
@!slipped.shift,
IterationEnd
),
nqp::if(
nqp::istype(pulled,Seq),
pulled.cache,
pulled
)
)
)
}
method is-lazy(--> True) { }
}
method Callable-xx-Whatever(&code) { Callable-xx-Whatever.new(&code) }
# Returns an iterator for a one character range of values. Takes the
# first, last character, and whether the first / last should be
# excluded.
my class CharFromTo does PredictiveIterator {
has int $!i;
has int $!n;
method !SET-SELF(\min,\max,\excludes-min,\excludes-max) {
$!i = nqp::ord(nqp::unbox_s(min))
- (excludes-min ?? 0 !! 1);
$!n = nqp::ord(nqp::unbox_s(max))
- (excludes-max ?? 1 !! 0);
self
}
method new(\min,\max,\excludes-min,\excludes-max) {
nqp::create(self)!SET-SELF(
min,max,excludes-min,excludes-max)
}
method pull-one() {
( $!i = $!i + 1 ) <= $!n
?? nqp::chr($!i)
!! IterationEnd
}
method skip-one() { ( $!i = $!i + 1 ) <= $!n }
method push-all(\target --> IterationEnd) {
my int $i = $!i;
my int $n = $!n;
target.push(nqp::chr($i)) while ($i = $i + 1) <= $n;
$!i = $i;
}
method count-only(--> Int:D) { nqp::p6box_i($!n - $!i) }
method sink-all(--> IterationEnd) { $!i = $!n }
}
method CharFromTo(\min,\max,\excludes-min,\excludes-max) {
CharFromTo.new(min,max,excludes-min,excludes-max)
}
# Return an iterator for a range of 0..^N with a number of elements.
# The third parameter indicates whether an IterationBuffer should be
# returned (1) for each combinatin, or a fully reified List (0).
# Has a highly optimized count-only, for those cases when one is only
# interested in the number of combinations, rather than the actual
# combinations. The workhorse of combinations().
my class Combinations does PredictiveIterator {
has int $!pulled-count = 0;
has int $!n;
has int $!k;
has int $!b;
has Mu $!stack;
has Mu $!combination;
method !SET-SELF(\n,\k,\b) {
nqp::stmts(
($!n = n),
($!k = k),
($!b = b),
($!stack := nqp::list_i(0)),
($!combination := nqp::create(IterationBuffer)),
self
)
}
method new(\n,\k,\b) { nqp::create(self)!SET-SELF(n,k,b) }
method pull-one() {
nqp::stmts(
(my int $n = $!n), # lexicals faster
(my int $k = $!k),
(my int $running = 1),
nqp::while(
($running && (my int $elems = nqp::elems($!stack))),
nqp::stmts(
(my int $index = nqp::sub_i($elems,1)),
(my int $value = nqp::pop_i($!stack)),
nqp::while(
(nqp::islt_i($value,$n)
&& nqp::islt_i($index,$k)),
nqp::stmts(
nqp::bindpos($!combination,
$index,nqp::clone($value)),
($index = nqp::add_i($index,1)),
($value = nqp::add_i($value,1)),
nqp::push_i($!stack,$value)
)
),
($running = nqp::isne_i($index,$k)),
)
),
nqp::if(
nqp::iseq_i($index,$k),
nqp::stmts(
($!pulled-count = nqp::add_i($!pulled-count,1)),
nqp::if(
$!b,
nqp::clone($!combination),
nqp::clone($!combination).List
)
),
IterationEnd
)
)
}
method count-only(--> Int:D) {
(([*] ($!n ... 0) Z/ 1 .. min($!n - $!k, $!k)).Int)
- $!pulled-count
}
}
method Combinations($n, $k, int $b) {
nqp::if(
$n > 0 && nqp::isbig_I(nqp::decont($n)), # must be HLL comparison
X::OutOfRange.new(
:what("First parameter"),
:got($n),
:range("-Inf^..{$?BITS == 32 ?? 2**28-1 !! 2**31-1}")
).throw,
nqp::if(
# k = 0 β can pick just 1 combination (empty list); return ((),)
$k == 0, # Must be HLL comparison
Rakudo::Iterator.OneValue(
nqp::create(nqp::if($b,IterationBuffer,List))
),
nqp::if(
# n < 1 β we have an empty list to pick from
# n < k β not enough items to pick combination of k items
$n < 1 || $n < $k || $k < 0, # must be HLL comparisons
Rakudo::Iterator.Empty, # nothing to return
Combinations.new($n,$k,$b)
)
)
)
}
# Return an iterator that will cross the given iterables (with &[,])
# Basically the functionality of @a X @b
my class CrossIterables does Iterator {
has $!iterators; # iterator per iterable, if any
has $!reifieds; # cached values (either complete, or so far)
has $!indices; # indices of virtual matrix of crossed values
has $!next; # IterationBuffer with next values to return
has int $!lazy; # whether the outer iterator is lazy
has int $!top; # index of top reified/iterator
method !SET-SELF(\iterables) {
nqp::stmts(
(my $iterables := nqp::getattr(iterables,List,'$!reified')),
(my int $elems = nqp::elems($iterables)),
($!iterators := nqp::setelems(nqp::list,$elems)),
($!reifieds := nqp::setelems(nqp::list,$elems)),
($!next :=
nqp::setelems(nqp::create(IterationBuffer),$elems)),
# loop over all iterables
(my int $i = -1),
nqp::while(
nqp::islt_i(($i = nqp::add_i($i,1)),$elems),
# set up initial value of index $i with...
nqp::bindpos($!next,$i,nqp::if(
nqp::iscont(my $elem := nqp::atpos($iterables,$i))
|| nqp::not_i(nqp::istype($elem,Iterable)),
# single value same as reified list of 1
nqp::bindpos(
nqp::bindpos($!reifieds,$i,nqp::list),
0,
$elem
),
# something more elaborate
nqp::if(
nqp::istype($elem,List)
&& nqp::not_i(nqp::isconcrete(
nqp::getattr($elem,List,'$!todo')
)),
# it's a List, may have a reified we can use directly
nqp::if(
nqp::isconcrete(
$elem := nqp::getattr($elem,List,'$!reified')
) && nqp::isgt_i(nqp::elems($elem),0),
# use the available reified directly
nqp::stmts(
nqp::bindpos($!reifieds,$i,$elem),
nqp::atpos($elem,0)
),
# cross with an empty list is always an empty list
return Rakudo::Iterator.Empty
),
# need to set up an iterator
nqp::stmts(
nqp::if($elem.is-lazy,($!lazy = 1)),
nqp::if(
nqp::eqaddr(
(my $pulled :=
($elem := $elem.iterator).pull-one),
IterationEnd
),
# cross with an empty list is an empty list
(return Rakudo::Iterator.Empty),
# set up the iterator stuff
nqp::stmts(
nqp::bindpos($!iterators,$i,$elem),
nqp::bindpos($!reifieds,$i,nqp::list($pulled)),
$pulled
)
)
)
)
))
),
# indices start with 0 xx $elems
($!indices := nqp::setelems(nqp::list_i,$elems)),
($!top = nqp::sub_i($elems,1)),
self
)
}
method new(\iterables) { nqp::create(self)!SET-SELF(iterables) }
method pull-one() {
nqp::if(
nqp::eqaddr($!next,IterationEnd),
IterationEnd,
nqp::stmts(
# set up result of this pull
(my $result := nqp::clone($!next).List),
# start working on next result
nqp::unless(
nqp::isnull(nqp::atpos($!iterators,$!top)),
# top level is still iterator, fetch
nqp::if(
nqp::eqaddr(
(my $pulled :=
nqp::atpos($!iterators,$!top).pull-one),
IterationEnd
),
# iterator no more
nqp::bindpos($!iterators,$!top,nqp::null),
# push value, let normal reifier handler handle
nqp::push(
nqp::atpos($!reifieds,$!top),
$pulled
)
)
),
# no iterator, must use reified list
nqp::if(
nqp::islt_i(
(my int $index =
nqp::add_i(nqp::atpos_i($!indices,$!top),1)),
nqp::elems(nqp::atpos($!reifieds,$!top))
),
# within range, update next result and index
nqp::bindpos($!next,$!top,
nqp::atpos(
nqp::atpos($!reifieds,$!top),
nqp::bindpos_i($!indices,$!top,$index)
)
),
# need to update lower levels
nqp::stmts(
# update topmost value (go back to first)
nqp::bindpos($!next,$!top,
nqp::atpos(
nqp::atpos($!reifieds,$!top),
nqp::bindpos_i($!indices,$!top,0)
)
),
# until we're at the bottom
(my int $level = $!top),
nqp::while(
nqp::isge_i(($level = nqp::sub_i($level,1)),0),
nqp::if(
nqp::isnull(nqp::atpos($!iterators,$level)),
# can use reified list at this level
nqp::if(