Merge pull request manwar#2899 from andemark/branch-for-challenge-089

ch-2.p6 simplified

Author: manwar

challenge-089/mark-anderson/raku/ch-2.p6

@@ -2,31 +2,56 @@
 # With help from https://www.wikihow.com/Solve-a-Magic-Square
 #
 
-use Scalar::History;
+=begin usage
+
+raku ch-2.p6
+
+[8 1 6]
+[3 5 7]
+[4 9 2]
+
+raku ch-2.p6 17
+
+[155 174 193 212 231 250 269 288   1  20  39  58  77  96 115 134 153]
+[173 192 211 230 249 268 287  17  19  38  57  76  95 114 133 152 154]
+[191 210 229 248 267 286  16  18  37  56  75  94 113 132 151 170 172]
+[209 228 247 266 285  15  34  36  55  74  93 112 131 150 169 171 190]
+[227 246 265 284  14  33  35  54  73  92 111 130 149 168 187 189 208]
+[245 264 283  13  32  51  53  72  91 110 129 148 167 186 188 207 226]
+[263 282  12  31  50  52  71  90 109 128 147 166 185 204 206 225 244]
+[281  11  30  49  68  70  89 108 127 146 165 184 203 205 224 243 262]
+[ 10  29  48  67  69  88 107 126 145 164 183 202 221 223 242 261 280]
+[ 28  47  66  85  87 106 125 144 163 182 201 220 222 241 260 279   9]
+[ 46  65  84  86 105 124 143 162 181 200 219 238 240 259 278   8  27]
+[ 64  83 102 104 123 142 161 180 199 218 237 239 258 277   7  26  45]
+[ 82 101 103 122 141 160 179 198 217 236 255 257 276   6  25  44  63]
+[100 119 121 140 159 178 197 216 235 254 256 275   5  24  43  62  81]
+[118 120 139 158 177 196 215 234 253 272 274   4  23  42  61  80  99]
+[136 138 157 176 195 214 233 252 271 273   3  22  41  60  79  98 117]
+[137 156 175 194 213 232 251 270 289   2  21  40  59  78  97 116 135]
+
+=end usage
 
 unit sub MAIN(UInt $n where * mod 2 = 3); #= a positive odd integer
 
 .say for odd-magic-square($n);
 
 sub odd-magic-square($n) {
-    subset Valid of UInt where 0 <= * < $n;
-
-    my $r := Scalar::History.create(0, Valid);
-    my $c := Scalar::History.create(($n / 2).floor, Valid); 
     my @matrix = [0 xx $n] xx $n;
-    @matrix[$r][$c] = 1; 
+    my $r = 1;
+    my $c = ($n / 2).floor - 1; 
 
-    for 2..($n**2) -> $num {
-        try $r--; if $! { $r = $n - 1 }
-        try $c++; if $! { $c = 0      } 
+    for 1..($n**2) -> $num {
+        $r = ($r - 1) mod $n;
+        $c = ($c + 1) mod $n;
 
         if @matrix[$r][$c] {
-            $r = $r.VAR.get-history.tail + 1;
-            $c = $c.VAR.get-history.tail;
+            $r = ($r + 1) mod $n + 1;
+            $c = ($c - 1) mod $n;
         }
 
         @matrix[$r][$c] = $num;
     }
 
-    @matrix.map(*.fmt("%{($n**2).chars}d").Array);
+    @matrix.map(*.fmt( "%{ ($n**2).chars }d" ).Array);
 }