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diff --git a/src/grid-geometry.lisp b/src/grid-geometry.lisp
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+;;; grid-geometry.lisp
+
+(in-package :wheelwork )
+
+(defmacro with-grid-line
+    ((x y) (start-x start-y) (end-x end-y) &body body)
+  "Execute BODY for X and Y assigned to integer values in a line
+connecting the integer point START-X , START-Y and END-X, END-Y. "
+  (with-gensyms (sx sy ex ey distance step progress xdiff ydiff)
+    `(loop
+       with ,sx = ,start-x
+       with ,sy = ,start-y
+       with ,ex = ,end-x
+       with ,ey = ,end-y
+       with ,xdiff = (- ,ex ,sx)
+       with ,ydiff = (- ,ey, sy)
+       with ,distance = (max (abs ,xdiff) (abs ,ydiff))
+       for ,step from 0 to ,distance
+       for ,progress = (if (zerop ,distance) 0.0 (/ ,step ,distance))
+       for ,x = (round (+ ,start-x (* ,progress ,xdiff)))
+       for ,y = (round (+ ,start-y (* ,progress ,ydiff)))
+       do (progn ,@body))))
+
+(defmacro with-grid-path
+    ((x y) (path &key autoclosep interiorp) &body body)
+  (with-gensyms (points x1 y1 x2 y2 more)
+    (let ((autoclose-block
+            (when autoclosep
+              `(destructuring-bind (,x2 ,y2) (first ,points)
+                 (with-grid-line (,x2 ,y2) (,x1 ,y1) ,@body))))) 
+      `(let ((,points ,path))
+         (loop
+           for ((,x1 ,y) (,x2 ,y2) . ,more) on ,points
+           while ,x2 do
+             (with-grid-line (,x ,y) (,x1 ,y1) (,x2 ,y2) ,@body)
+           finally (progn ,autoclose-block))))))
+
+(defun grid-bbox-for (poly)
+  "POLY is a list of pairs of xy coordinates. Return a pair of
+pairs, ((min-x min-y) (max-x max-y)), representing the bottom left and
+top right corners of the bounding box for POLY "
+  (loop for (x y) in poly
+        minimizing x into x-min
+        maximizing x into x-max
+        minimizing y into y-min
+        maximizing y into y-max
+        finally (return (list (list x-min y-min)
+                              (list x-max y-max)))))
+
+(defmacro with-grid-poly-interior
+    ((x y) perimeter &body body)
+  "PERMIETER is expected to evaluate to a list of contiguous points,
+representing the permimeter a polygon in 2d space. Execute BODY for
+each point interior to this polygon."
+  (with-gensyms (points bottom left top right)
+    `(let ((,points ,permieter))
+       (destructuring-bind ((,left ,bottom) (,right ,top)) (grid-bbox-for ,points)
+         (loop )
+         )))
+  )
+
+(defmacro with-grid-circle
+    ((x y) (cx cy radius &key interiorp) &body body)
+  (with-gensyms (rad sx sy)
+    (let ((comparator
+            (if interiorp '>= '=))) 
+      `(let ((,sx ,cx) (,sy ,cy) (,rad ,radius)) 
+         (with-grid-rect (,x ,y) ((- ,sx ,rad) (- ,sy ,rad) (+ ,sx ,rad) (+ ,sy ,rad))
+           (when (,comparator ,rad (round (euclidean-dist ,x ,y ,sx ,sy)))
+             ,@body))))))