1 files changed, 135 insertions, 0 deletions
diff --git a/pgu/algo.py b/pgu/algo.py
new file mode 100644
index 0000000..dedb020
--- /dev/null
+++ b/pgu/algo.py
@@ -0,0 +1,135 @@
+"""Some handy algorithms for use in games, etc.
+
+<p>please note that this file is alpha, and is subject to modification in
+future versions of pgu!</p>
+"""
+print 'pgu.algo','This module is alpha, and is subject to change.'
+
+#def dist(a,b):
+#    return abs(a[0]-b[0]) + abs(a[1]-b[1])
+    
+class node:
+    def __init__(self,prev,pos,dest):
+        self.prev,self.pos,self.dest = prev,pos,dest
+        if self.prev == None: self.g = 0
+        else: self.g = self.prev.g + 1
+        self.h = dist(pos,dest)
+        self.f = self.g+self.h
+
+
+def astar(start,end,layer,_dist):
+    """uses the a* algorithm to find a path
+    
+    <pre>astar(start,end,layer,dist): return [list of positions]</pre>
+    
+    <dl>
+    <dt>start<dd>start position
+    <dt>end<dd>end position
+    <dt>layer<dd>a grid where zero cells are open and non-zero cells are walls
+    <dt>dist<dd>a distance function dist(a,b)
+    </dl>
+    
+    <p>returns a list of positions from start to end</p>
+    """
+    global dist
+    dist = _dist
+    if layer[start[1]][start[0]]: return [] #start is blocked
+    if layer[end[1]][end[0]]: return [] #end is blocked
+    w,h = len(layer[0]),len(layer)
+    if start[0] < 0 or start[1] < 0 or start[0] >= w or start[1] >= h: return [] #start outside of layer
+    if end[0] < 0 or end[1] < 0 or end[0] >= w or end[1] >= h: return [] #end outside of layer
+
+    opens = []
+    open = {}
+    closed = {}
+    cur = node(None,start,end)
+    open[cur.pos] = cur
+    opens.append(cur)
+    while len(open):
+        cur = opens.pop(0)
+        if cur.pos not in open: continue
+        del open[cur.pos]
+        closed[cur.pos] = cur
+        if cur.pos == end: break
+        for dx,dy in [(0,-1),(1,0),(0,1),(-1,0)]:#(-1,-1),(1,-1),(-1,1),(1,1)]:
+            x,y = pos = cur.pos[0]+dx,cur.pos[1]+dy
+            if layer[y][x]: continue
+            #check for blocks of diagonals
+            if layer[cur.pos[1]+dy][cur.pos[0]]: continue
+            if layer[cur.pos[1]][cur.pos[0]+dx]: continue
+            new = node(cur,pos,end)
+            if pos in open and new.f >= open[pos].f: continue
+            if pos in closed and new.f >= closed[pos].f: continue
+            if pos in open: del open[pos]
+            if pos in closed: del closed[pos]
+            open[pos] = new
+            lo = 0
+            hi = len(opens)
+            while lo < hi:
+                mid = (lo+hi)/2
+                if new.f < opens[mid].f: hi = mid
+                else: lo = mid + 1
+            opens.insert(lo,new)
+    
+    if cur.pos != end: 
+        return []
+                    
+    path = []
+    while cur.prev != None:
+        path.append(cur.pos)
+        cur = cur.prev
+    path.reverse()
+    return path
+    
+
+def getline(a,b):
+    """returns a path of points from a to b
+    
+    <pre>getline(a,b): return [list of points]</pre>
+    
+    <dl>
+    <dt>a<dd>starting point
+    <dt>b<dd>ending point
+    </dl>
+    
+    <p>returns a list of points from a to b</p>
+    """
+           
+    path = []
+    
+    x1,y1 = a
+    x2,y2 = b
+    dx,dy = abs(x2-x1),abs(y2-y1)
+
+    if x2 >= x1: xi1,xi2 = 1,1
+    else: xi1,xi2 = -1,-1
+    
+    if y2 >= y1: yi1,yi2 = 1,1
+    else: yi1,yi2 = -1,-1
+    
+    if dx >= dy:
+        xi1,yi2 = 0,0
+        d = dx
+        n = dx/2
+        a = dy
+        p = dx
+    else:
+        xi2,yi1 = 0,0
+        d = dy
+        n = dy/2
+        a = dx
+        p = dy
+        
+    x,y = x1,y1
+    c = 0
+    while c <= p:
+        path.append((x,y))
+        n += a
+        if n > d: 
+            n -= d
+            x += xi1
+            y += yi1
+        x += xi2
+        y += yi2
+        c += 1
+    return path