adds priority queuing

.directory

@@ -0,0 +1,6 @@
+[Dolphin]
+Timestamp=2019,2,3,21,5,9
+Version=4
+
+[Settings]
+HiddenFilesShown=true

.vscode/multibow.code-workspace

@@ -1,7 +1,7 @@
 {
 	"folders": [
 		{
-			"path": "."
+			"path": ".."
 		}
 	],
 	"settings": {
@@ -13,4 +13,4 @@
 		"lua.luacheckPath": "luacheck",
 		"lua.preferLuaCheckErrors": true
 	}
-}
+}

sdcard/snippets/mb/prioqueue.lua

@@ -0,0 +1,86 @@
+--[[
+Copyright 2019 Harald Albrecht
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+]]--
+
+local pq = {}
+
+pq.__index = pq
+
+-- luacheck: ignore 212/self
+function pq:new()
+    local slf = {}
+    setmetatable(slf, pq)
+    slf.heap = {}
+    slf.size = 0
+    return slf
+end
+
+function pq:peek()
+    if self.size > 0 then
+        return self.heap[1].priority, self.heap[1].value
+    end
+    return nil, nil
+end
+
+function pq:add(priority, value)
+    self.size = self.size + 1
+    self.heap[self.size] = {priority=priority, value=value}
+    -- let the new element move up the heap as far as necessary.
+    local i = self.size
+    while math.floor(i/2) > 0 do
+        local half = math.floor(i/2)
+        if self.heap[i].priority < self.heap[half].priority then
+            self.heap[i], self.heap[half] = self.heap[half], self.heap[i]
+        end
+        i = half
+    end
+end
+
+function pq:remove()
+    if self.size == 0 then
+        return nil, nil
+    end
+    local pv = self.heap[1]
+    self.heap[1] = self.heap[self.size]
+    self.heap[self.size] = nil
+    self.size = self.size - 1
+    --
+    local i = 1
+    while i*2 <= self.size do
+        local minchild = self:minchild(i)
+        if self.heap[i].priority > self.heap[minchild].priority then
+            self.heap[i], self.heap[minchild] = self.heap[minchild], self.heap[i]
+        end
+        i = minchild
+    end
+    --
+    return pv.priority, pv.value
+end
+
+function pq:minchild(i)
+    local i2 = i*2
+    if i2+1 > self.size then
+        return i2
+    end
+    return self.heap[i2].priority < self.heap[i2+1].priority and i2 or i2+1
+end
+
+return pq

spec/snippets/prioqueue_spec.lua

@@ -0,0 +1,53 @@
+--[[
+Copyright 2019 Harald Albrecht
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+]]--
+
+local pq = require("snippets/mb/prioqueue")
+
+describe("prioqueue", function()
+
+    it("adds and peeks", function()
+        local q = pq.new()
+        q:add(200, "foo")
+        q:add(100, "bar1")
+        q:add(300, "zoo")
+        q:add(100, "bar2")
+
+        assert.is.equal(4, q.size)
+
+        local p, v = q:peek()
+        assert.is.same({100, "bar1"}, {p, v})
+
+        p, v = q:remove()
+        assert.is.same({100, "bar1"}, {p, v})
+        p, v = q:remove()
+        assert.is.same({100, "bar2"}, {p, v})
+        p, v = q:remove()
+        assert.is.same({200, "foo"}, {p, v})
+        p, v = q:remove()
+        assert.is.same({300, "zoo"}, {p, v})
+
+        p, v = q:peek()
+        assert.is.falsy(p)
+        assert.is.falsy(v)
+    end)
+
+end)