Data commit

Task/Zig-zag-matrix/M4/zig-zag-matrix.m4

@@ -0,0 +1,30 @@
+divert(-1)
+
+define(`set2d',`define(`$1[$2][$3]',`$4')')
+define(`get2d',`defn(`$1[$2][$3]')')
+define(`for',
+   `ifelse($#,0,``$0'',
+   `ifelse(eval($2<=$3),1,
+   `pushdef(`$1',$2)$4`'popdef(`$1')$0(`$1',incr($2),$3,`$4')')')')
+define(`show2d',
+   `for(`x',0,decr($2),
+      `for(`y',0,decr($3),`format(`%2d',get2d($1,x,y)) ')
+')')
+
+dnl  <name>,<size>
+define(`zigzag',
+   `define(`j',1)`'define(`k',1)`'for(`e',0,eval($2*$2-1),
+      `set2d($1,decr(j),decr(k),e)`'ifelse(eval((j+k)%2),0,
+         `ifelse(eval(k<$2),1,
+            `define(`k',incr(k))',
+            `define(`j',eval(j+2))')`'ifelse(eval(j>1),1,
+            `define(`j',decr(j))')',
+         `ifelse(eval(j<$2),1,
+            `define(`j',incr(j))',
+            `define(`k',eval(k+2))')`'ifelse(eval(k>1),1,
+            `define(`k',decr(k))')')')')
+
+divert
+
+zigzag(`a',5)
+show2d(`a',5,5)