Reimplement List.reduce in Perl6.

[p6rt]

Migrated from rt.perl.org#63698 (status was 'resolved')

Searchable as RT63698$

[p6rt]

From @bacek

---

src/builtins/any-list.pir | 61 --------------------------------------------- src/setting/Any-list.pm | 24 +++++++++++++++++ 2 files changed, 24 insertions(+), 61 deletions(-)

[p6rt]

From @bacek

4603381c4d4c0b311ee3f6276a79bbb637013670.diff

```diff diff --git a/src/builtins/any-list.pir b/src/builtins/any-list.pir index 1967fbf..b87666b 100644 --- a/src/builtins/any-list.pir +++ b/src/builtins/any-list.pir @@ -429,67 +429,6 @@ Return a List with the keys of the invocant. .tailcall self.'pick'($I0) .end -=item reduce(...) - -=cut - -.namespace [] -.sub 'reduce' :multi('Sub') - .param pmc expression - .param pmc values :slurpy - .tailcall values.'reduce'(expression) -.end - -.namespace ['Any'] -.sub 'reduce' :method :multi(_, 'Sub') - .param pmc expression - .local pmc retv - .local pmc iter - .local pmc elem - .local pmc args - .local int i, arity - - arity = expression.'arity'() - if arity < 2 goto error - - iter = self.'iterator'() - unless iter goto empty - retv = shift iter - loop: - unless iter goto done - - # Create arguments for closure - args = new 'ResizablePMCArray' - # Start with 1. First argument is result of previous call - i = 1 - - args_loop: - if i == arity goto invoke - unless iter goto elem_undef - elem = shift iter - goto push_elem - elem_undef: - elem = 'undef'() - - push_elem: - push args, elem - inc i - goto args_loop - - invoke: - retv = expression(retv, args :flat) - goto loop - - empty: - .tailcall '!FAIL'('Cannot reduce an empty list') - - error: - 'die'('Cannot reduce() using a unary or nullary function.') - - done: - .return(retv) -.end - =item sort() diff --git a/src/setting/Any-list.pm b/src/setting/Any-list.pm index 3849a86..5758dce 100644 --- a/src/setting/Any-list.pm +++ b/src/setting/Any-list.pm @@ -3,6 +3,26 @@ class Any is also { gather { take $_ if $test($_) for $values.list; } + }; + + multi method reduce( $values: Code $expression ) { + my $arity = $expression.arity; + die('Cannot reduce() using a unary or nullary function.') if $arity < 2; + + my @list = $values.list; + fail ('Cannot reduce() empty list') if @list.elems == 0; + + my $res = shift @list; + $arity--; + while @list { + my @args = @list.splice(0, $arity); + if @args.elems < $arity { + # Extend args if list exausted early + @args.push(undef x ($arity - @args.elems)); + } + $res = &$expression($res, |@args); + } + $res; } } @@ -10,4 +30,8 @@ our List multi grep(Code $test, *@values) { @values.grep($test) } +multi reduce ( Code $expression ;; *@values ) { + @values.reduce($expression); +} + # vim: ft=perl6 ```

[p6rt]

From @bacek

After some discussions on #perl6 I've created new version of Any.reduce.

pmichaud++ as usual :)

-- Bacek

[p6rt]

From @bacek

---

src/builtins/any-list.pir | 61 --------------------------------------------- src/setting/Any-list.pm | 21 ++++++++++++++- 2 files changed, 20 insertions(+), 62 deletions(-)

Inline Patch

```diff diff --git a/src/builtins/any-list.pir b/src/builtins/any-list.pir index a61edd5..6540465 100644 --- a/src/builtins/any-list.pir +++ b/src/builtins/any-list.pir @@ -296,67 +296,6 @@ Return a List with the keys of the invocant. .tailcall self.'pick'($I0) .end -=item reduce(...) - -=cut - -.namespace [] -.sub 'reduce' :multi('Sub') - .param pmc expression - .param pmc values :slurpy - .tailcall values.'reduce'(expression) -.end - -.namespace ['Any'] -.sub 'reduce' :method :multi(_, 'Sub') - .param pmc expression - .local pmc retv - .local pmc iter - .local pmc elem - .local pmc args - .local int i, arity - - arity = expression.'arity'() - if arity < 2 goto error - - iter = self.'iterator'() - unless iter goto empty - retv = shift iter - loop: - unless iter goto done - - # Create arguments for closure - args = new 'ResizablePMCArray' - # Start with 1. First argument is result of previous call - i = 1 - - args_loop: - if i == arity goto invoke - unless iter goto elem_undef - elem = shift iter - goto push_elem - elem_undef: - elem = 'undef'() - - push_elem: - push args, elem - inc i - goto args_loop - - invoke: - retv = expression(retv, args :flat) - goto loop - - empty: - .tailcall '!FAIL'('Cannot reduce an empty list') - - error: - 'die'('Cannot reduce() using a unary or nullary function.') - - done: - .return(retv) -.end - =item sort() diff --git a/src/setting/Any-list.pm b/src/setting/Any-list.pm index 9af5a33..5cb7ed6 100644 --- a/src/setting/Any-list.pm +++ b/src/setting/Any-list.pm @@ -3,7 +3,22 @@ class Any is also { gather { take $_ if $test($_) for $values.list; } - } + }; + + multi method reduce(Code $expression) { + my Int $arity = $expression.count; + die('Cannot reduce() using a unary or nullary function.') if $arity < 2; + + my $list := @.list or fail('Cannot reduce() empty list'); + + my $res = $list.shift; + while $list { + my @args = gather { take $list.shift if $list for 2..$arity }; + $res = &$expression($res, |@args); + } + + $res; + }; our List multi method map(Code *&expr) { return gather { @@ -52,6 +67,10 @@ our List multi grep(Code $test, *@values) { @values.grep($test) } +multi reduce ( Code $expression ;; *@values ) { + @values.reduce($expression); +} + our List multi map(Code $expr, *@values) { @values.map($expr) } -- 1.6.2.rc0 ```

[p6rt]

From @bacek

Hello.

This one is latest vesion. Sorry for messing with git-send-email :-/

-- Bacek

[p6rt]

@bacek - Status changed from 'new' to 'open'

[p6rt]

From @pmichaud

On Tue, Mar 10, 2009 at 03​:40​:20AM -0700, Vasily Chekalkin wrote​:

+ multi method reduce(Code $expression) { + my Int $arity = $expression.count; + die('Cannot reduce() using a unary or nullary function.') if $arity \< 2; + + my $list := @​.list or fail('Cannot reduce() empty list');

Why is one condition 'die' and the other condition 'fail'?

+ my $res = $list.shift;

Note that $list might not be something that can be shifted -- 'shift' is only available for Arrays and Iterators.

So, patch rejected, at least this version of it.

Pm

[p6rt]

From @bacek

On Sat Mar 07 16​:14​:01 2009, bacek wrote​:

--- src/builtins/any-list.pir | 61 --------------------------------------------- src/setting/Any-list.pm | 24 +++++++++++++++++ 2 files changed, 24 insertions(+), 61 deletions(-)

After few iterations moritz++ implemented final version. Resolving ticket.

-- Bacek

[p6rt]

@bacek - Status changed from 'open' to 'resolved'