From c8e5f1e67788976ff65611fbf77b3be13bffd79a Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Thu, 4 Apr 2024 00:33:07 +0100
Subject: launch cactus

---
 cactus.dat  |  1 +
 cactus.lua  | 50 +++++++++++++++++++++++++++++++++++++++-----------
 numutil.lua | 11 +++++++++++
 3 files changed, 51 insertions(+), 11 deletions(-)
 create mode 100644 cactus.dat
 create mode 100644 numutil.lua

diff --git a/cactus.dat b/cactus.dat
new file mode 100644
index 0000000..c00c3d5
--- /dev/null
+++ b/cactus.dat
@@ -0,0 +1 @@
+dep numutil
diff --git a/cactus.lua b/cactus.lua
index 6613df5..982d987 100644
--- a/cactus.lua
+++ b/cactus.lua
@@ -1,3 +1,5 @@
+local numutil = require 'numutil'
+
 local function ensure_equipped(ptype, item)
 	local cur = peripheral.getType"left"
 	print(cur)
@@ -15,17 +17,21 @@ end
 local function ensure_modem() return ensure_equipped("modem","computercraft:wireless_modem_normal") end
 local function ensure_scanner() return error("aaa") end
 
-assert(ensure_modem())
+local function turte_pos_init()
+	assert(ensure_modem())
+
+	local POS = vector.new(gps.locate())
 
-local POS = vector.new(gps.locate())
-local function get_facing()
 	while turtle.detect() do turtle.turnRight() end
 	turtle.forward()
 	local newpos = vector.new(gps.locate())
 	turtle.back()
-	return newpos - POS
+	local FACING = newpos - POS
+
+	return POS, FACING
 end
-local FACING = get_facing()
+
+local POS, FACING = turte_pos_init()
 
 local function moveby_y(delta)
 	local fn = turtle.up
@@ -34,7 +40,7 @@ local function moveby_y(delta)
 end
 
 local function rotatev(v,nq)
-	-- rotates v by n quarters
+	-- rotates v by n quarters, clockwise (rightwards)
 	nq = nq%4
 	if nq == 0     then return vector.new( v.x,  v.y,  v.z)
 	elseif nq == 1 then return vector.new(-v.z,  v.y,  v.x)
@@ -43,15 +49,37 @@ local function rotatev(v,nq)
 	end
 end
 
-local v = vector.new(1,0,2)
-for i=0,4 do print(i,rotatev(v,i)) end
-
-local function moveby_xz(dv)
-	-- y component of dv is ignored
+local function turn_right()
+	FACING = rotatev(FACING,1)
+	turtle.turnRight()
+end
+local function turn_left()
+	FACING = rotatev(FACING,-1)
+	turtle.turnLeft()
+end
 
+local function turn_to_face(newfacing)
+	if newfacing == FACING then return
+	elseif newfacing == -FACING then turtle.turnRight() turtle.turnRight()
+	elseif newfacing == rotatev(FACING,1) then turtle.turnRight()
+	elseif newfacing == rotatev(FACING,-1) then turtle.turnLeft()
+	else error("invalid facing "..tostring(newfacing))
+	end
 end
 
+local function moveby_xz(dv)
+	turn_to_face(vector.new(numutil.sign(dv.x), 0, 0))
+	for i=1,math.abs(dv.x) do turtle.forward() end
+	turn_to_face(vector.new(0, 0, numutil.sign(dv.z)))
+	for i=1,math.abs(dv.z) do turtle.forward() end
+end
 
+local function moveby(delta)
+	moveby_y(delta.y)
+	moveby_xz(delta)
+end
 
 
 local datum = vector.new(-18, 128, -1837)
+local delta = datum - POS
+moveby(delta)
diff --git a/numutil.lua b/numutil.lua
new file mode 100644
index 0000000..ce212c4
--- /dev/null
+++ b/numutil.lua
@@ -0,0 +1,11 @@
+local function sign(x)
+	if x > 0 then return 1
+	elseif x < 0 then return -1
+	else return 0
+	end
+end
+
+
+return {
+	sign = sign,
+}
-- 
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