# New Ticket Created by David Whipp
# Please include the string: [perl #84362]
# in the subject line of all future correspondence about this issue.
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=84362 >
Attached patches add tests and implementation for sequence operator with
limit-function arity > 1 (the function is assumed to be false until we have
enough values to call it). The tests show how this can be used to terminate
a sequence when it converges, or when a specific curvature is seen:
1, */2 ... abs(*-*) < 0.01; ## convergence: 8 values
0,1,2,1,0,1,2 ...^ { $^a-$^b > $^b-$^c }; ## curvature: 5 values
1,2 ... { @_ == 4 }; ## length: 4 values
>From 608d6c1dc96b81e0537d670d9949451c227f5708 Mon Sep 17 00:00:00 2001
From: Dave Whipp <dwh...@google.com>
Date: Thu, 17 Feb 2011 12:08:45 -0800
Subject: [PATCH] tests of sequence operator with limit function having arity > 1
---
S03-sequence/limit-arity-2-or-more.t | 37 ++++++++++++++++++++++++++++++++++
1 files changed, 37 insertions(+), 0 deletions(-)
create mode 100644 S03-sequence/limit-arity-2-or-more.t
diff --git a/S03-sequence/limit-arity-2-or-more.t b/S03-sequence/limit-arity-2-or-more.t
new file mode 100644
index 0000000..5524ea8
--- /dev/null
+++ b/S03-sequence/limit-arity-2-or-more.t
@@ -0,0 +1,37 @@
+use v6;
+use Test;
+
+# L<S03/List infix precedence/"the sequence operator">
+
+plan 8;
+
+# sequence with a limit function of arity 2
+
+is (8,*/2 ... abs(*-*) < 2).join(', '), '8, 4, 2, 1', 'arity-2 convergence limit';
+is (8,*/2 ...^ abs(*-*) < 2).join(', '), '8, 4, 2', 'arity-2 excluded convergence limit';
+
+# sequence with a limit function of arity 3
+
+{
+ my $i = -5;
+ my @seq = { ++$i; $i**3-9*$i } ... { ($^a-$^b) > ($^b-$^c) };
+ is @seq.join(', '), '-28, 0, 10, 8, 0, -8, -10', 'arity-3 curvature limit';
+}
+
+{
+ my $i = -5;
+ my @seq = { ++$i; $i**3-9*$i } ...^ { ($^a-$^b) > ($^b-$^c) };
+ is @seq.join(', '), '-28, 0, 10, 8, 0, -8', 'arity-3 excluded curvature limit';
+}
+
+# limit functions that limit sequence exactly at arity limit
+
+is (2, 1, 0.5 ... abs(*-*) < 2).join(', '), '2, 1', 'ASAP arity-2 convergence limit';
+is (2, 1, 0.5 ...^ abs(*-*) < 2).join(', '), '2', 'ASAP arity-2 excluded convergence limit';
+
+# limit function that accepts any number of args
+
+is (1 ... { @_ eq "1 2 3" }).join(', '), '1, 2, 3', 'arity-Inf limit';
+is (1 ...^ { @_ eq "1 2 3" }).join(', '), '1, 2', 'arity-Inf excluded limit';
+
+done;
--
1.7.3.1
>From de547c7c44810e1cd8d03c023cc380498bff6301 Mon Sep 17 00:00:00 2001
From: Dave Whipp <dwh...@google.com>
Date: Thu, 17 Feb 2011 12:07:27 -0800
Subject: [PATCH] Sequence operator supports limit functions with arity > 1
---
src/core/operators.pm | 30 ++++++++++++++++++++++--------
1 files changed, 22 insertions(+), 8 deletions(-)
diff --git a/src/core/operators.pm b/src/core/operators.pm
index c92e9f2..074db9f 100644
--- a/src/core/operators.pm
+++ b/src/core/operators.pm
@@ -401,16 +401,30 @@ our sub _HELPER_generate-series(@lhs, $rhs , :$exclude-limit) {
my $limit = ($rhs ~~ Whatever ?? Any !! $rhs);
return infinite-series(@lhs , $limit) if $rhs ~~ Whatever; #shortcut infinite series so we avoid the comparisions
- fail ('Limit arity cannot be larger than 1') if $limit ~~ Code && $limit.count > 1;
+ #fail ('Limit arity cannot be larger than 1') if $limit ~~ Code && $limit.count > 1;
my $series = infinite-series(@lhs , $limit);
+
gather {
- while $series {
- my $val = $series.shift();
- if $val ~~ $limit {
- take $val unless $exclude-limit ;
- last ;
- };
- take $val;
+ if $limit ~~ Code && $limit.count > 1 {
+ my @limit-args;
+ while $series {
+ @limit-args.shift if @limit-args == $limit.count;
+ my $val = $series.shift;
+ @limit-args.push($val);
+ my $done = @limit-args >= $limit.arity && $limit(|@limit-args);
+ take $val unless $done && $exclude-limit;
+ last if $done;
+ }
+ }
+ else {
+ while $series {
+ my $val = $series.shift();
+ if $val ~~ $limit {
+ take $val unless $exclude-limit ;
+ last ;
+ };
+ take $val;
+ }
}
}
}
--
1.7.3.1
