From 287beaf53f83c0718b90ac7b307bc335d69cfdcd Mon Sep 17 00:00:00 2001
From: Mark <53903062+andemark@users.noreply.github.com>
Date: Sat, 24 Feb 2024 00:51:03 +0000
Subject: ch-2.raku simplified

---
 challenge-257/mark-anderson/raku/ch-2.raku | 185 +++++++++++++++++------------
 1 file changed, 111 insertions(+), 74 deletions(-)

diff --git a/challenge-257/mark-anderson/raku/ch-2.raku b/challenge-257/mark-anderson/raku/ch-2.raku
index f61ebc906a..23ba966e1c 100644
--- a/challenge-257/mark-anderson/raku/ch-2.raku
+++ b/challenge-257/mark-anderson/raku/ch-2.raku
@@ -1,88 +1,125 @@
 #!/usr/bin/env raku
+use v6.e.PREVIEW; # for snip
 use Test;
 
-ok  reduced-row-echelon([1, 0, 0, 1],
-                        [0, 1, 0, 2],
-                        [0, 0, 1, 3]);
-
-nok reduced-row-echelon([1, 1, 0],
-                        [0, 1, 0],
-                        [0, 0, 0]);
-
-ok  reduced-row-echelon([0, 1,-2, 0, 1],
-                        [0, 0, 0, 1, 3],
-                        [0, 0, 0, 0, 0],
-                        [0, 0, 0, 0, 0]);
-
-ok  reduced-row-echelon([1, 0, 0, 4],
-                        [0, 1, 0, 7],
-                        [0, 0, 1,-1]);
-
-nok reduced-row-echelon([0, 1,-2, 0, 1],
-                        [0, 0, 0, 0, 0],
-                        [0, 0, 0, 1, 3],
-                        [0, 0, 0, 0, 0]);
-
-nok reduced-row-echelon([0, 1, 0],
-                        [1, 0, 0],
-                        [0, 0, 0]);
-
-nok reduced-row-echelon([4, 0, 0, 0],
-                        [0, 1, 0, 7],
-                        [0, 0, 1,-1]);
-
-nok reduced-row-echelon([1, 0, 0, 0],
-                        [0, 1, 0, 3],
-                        [0, 0, 1,-3],
-                        [0, 0, 0, 1],
-                        [0, 0, 0, 0]);
-
-nok reduced-row-echelon([1, 0, 0, 0],
-                        [0, 1, 0, 1],
-                        [0, 0, 1, 0],
-                        [0, 0, 0, 1],
-                        [0, 0, 0, 0]);
-
-ok  reduced-row-echelon([1, 0, 0, 0, 0],
-                        [0, 1, 0, 0, 0],
-                        [0, 0, 0, 0, 1],
-                        [0, 0, 0, 0, 0],
-                        [0, 0, 0, 0, 0]);
-
-ok  reduced-row-echelon([0, 0, 0],
-                        [0, 0, 0],
-                        [0, 0, 0],
-                        [0, 0, 0]);
-
-sub reduced-row-echelon(+@m)
+ok  RREF([
+             [1, 0, 0, 1],
+             [0, 1, 0, 2],
+             [0, 0, 1, 3]
+         ]);
+
+nok RREF([
+             [1, 1, 0],
+             [0, 1, 0],
+             [0, 0, 0]
+         ]);
+
+ok  RREF([
+             [0, 1,-2, 0, 1],
+             [0, 0, 0, 1, 3],
+             [0, 0, 0, 0, 0],
+             [0, 0, 0, 0, 0]
+         ]);
+
+ok  RREF([
+             [1, 0, 0, 4],
+             [0, 1, 0, 7],
+             [0, 0, 1,-1]
+         ]);
+
+nok RREF([
+             [0, 1,-2, 0, 1],
+             [0, 0, 0, 0, 0],
+             [0, 0, 0, 1, 3],
+             [0, 0, 0, 0, 0]
+         ]);
+
+nok RREF([
+             [0, 1, 0],
+             [1, 0, 0],
+             [0, 0, 0]
+         ]);
+
+nok RREF([
+             [4, 0, 0, 0],
+             [0, 1, 0, 7],
+             [0, 0, 1,-1]
+         ]);
+
+nok RREF([
+             [1, 0, 0, 0],
+             [0, 1, 0, 3],
+             [0, 0, 1,-3],
+             [0, 0, 0, 1],
+             [0, 0, 0, 0]
+         ]);
+
+nok RREF([
+             [1, 0, 0, 0],
+             [0, 1, 0, 1],
+             [0, 0, 1, 0],
+             [0, 0, 0, 1],
+             [0, 0, 0, 0]
+         ]);
+
+ok  RREF([
+             [1, 0, 0, 0, 0],
+             [0, 1, 0, 0, 0],
+             [0, 0, 0, 0, 1],
+             [0, 0, 0, 0, 0],
+             [0, 0, 0, 0, 0]
+         ]);
+
+ok  RREF([
+             [0, 0, 0],
+             [0, 0, 0],
+             [0, 0, 0],
+             [0, 0, 0]
+         ]);
+
+ok  RREF([
+             [0, 0, 0],
+         ]);
+
+ok  RREF([
+             [0, 1, 0],
+         ]);
+
+nok RREF([
+             [5],
+         ]);
+
+multi RREF(@m where all(.head) == 0)
 {
-    # the first non-zero number in a row is the pivot
-    my @pivots = @m>>.first(*.so, :kv);
+    all @m[1..*].map(*.all == 0)
+}
+
+multi RREF(@m)
+{
+    # group rows according to whether they are all-zero or not 
+    @m .= snip(|(*.any, *.any.not) xx *); 
 
-    # the first row that is all zeroes
-    my $k = @pivots.first(*.not, :k);
+    # at least one all-zero row occurs in the middle
+    return False if @m.elems > 2;
 
-    # rows with all zeroes are grouped at the bottom
-    with $k 
-    { 
-        return False unless all(@pivots[$k..*]) eqv Any; 
-        @pivots = @pivots[^$k];
-        return True unless @pivots
-    }
+    # remove any all-zero rows grouped at the bottom
+    @m = @m[0;*];
 
-    my @cols   = @pivots>>[0];
-       @pivots = @pivots>>[1];
+    # the first non-zero number in a row is the pivot. store the indices in @cols
+    my @cols = @m>>.first(*.any, :k);
 
-    # pivots go from top-left to bottom-right
+    # the pivots go from top-left to bottom-right
     return False unless [<] @cols;
 
-    # remove zero rows and non-pivot columns
-    @m = @m[^@pivots;@cols].batch(@cols.elems)>>.Array;
-    # @m should be an identity matrix at this point if it is RREF
+    # remove any non-pivot columns
+    @m = @m[*;@cols].batch(@cols.elems)>>.Array;
+
+    # @m will be an identity matrix now if it was in reduced row echelon form
+    # 🤓
 
     # all pivots are ones
-    return False unless all(@m.keys.map({ |@m[$_].splice($_,1) })) == 1; 
+    return False unless all(@m.keys.map({ |@m[$_].splice($_,1) })) == 1;
 
-    # everything else is zeroes
-    return all(@m[*;*]) == 0 
+    # everything else is a zero
+    return all(@m[*;*]) == 0
 }
-- 
cgit