September Morn Update

Task/Priority-queue/Phix/priority-queue-2.phix

@@ -0,0 +1,51 @@
+sequence pq = {}
+
+constant PRIORITY = 2
+
+procedure pq_add(sequence item)
+-- item is {object data, object priority}
+    integer n = length(pq)+1,
+            m = floor(n/2)
+    pq &= 0
+    -- append at end, then up heap
+    while m>0 and item[PRIORITY]<pq[m][PRIORITY] do
+        pq[n] = pq[m]
+        n = m
+        m = floor(m/2)
+    end while
+    pq[n] = item
+end procedure
+
+function pq_pop()
+    sequence result = pq[1]
+
+    integer qn = length(pq),
+            n = 1,
+            m = 2
+    while m<qn do
+        if m+1<qn and pq[m][PRIORITY]>pq[m+1][PRIORITY] then
+            m += 1
+        end if
+        if pq[qn][PRIORITY]<=pq[m][PRIORITY] then exit end if
+        pq[n] = pq[m]
+        n = m
+        m = m * 2
+    end while
+    pq[n] = pq[qn]
+    pq = pq[1..$-1]
+    return result
+end function
+
+constant set = shuffle({{"Clear drains", 3},
+                        {"Feed cat", 4},
+                        {"Make tea", 5},
+                        {"Solve RC tasks", 1},
+                        {"Tax return", 2}})
+for i=1 to length(set) do
+    pq_add(set[i])
+    pq_add(set[rand(length(set))])
+end for
+
+while length(pq) do
+    ?pq_pop()
+end while