diff --git a/compiler/src/prog8/ast/processing/AstChecker.kt b/compiler/src/prog8/ast/processing/AstChecker.kt
index 31992c0ca..10e3efba8 100644
--- a/compiler/src/prog8/ast/processing/AstChecker.kt
+++ b/compiler/src/prog8/ast/processing/AstChecker.kt
@@ -814,6 +814,14 @@ internal class AstChecker(private val program: Program,
         val targetStatement = checkFunctionOrLabelExists(functionCall.target, stmtOfExpression)
         if(targetStatement!=null)
             checkFunctionCall(targetStatement, functionCall.args, functionCall.position)
+
+        // warn about sgn(unsigned) this is likely a mistake
+        if(functionCall.target.nameInSource.last()=="sgn") {
+            val sgnArgType = functionCall.args.first().inferType(program)
+            if(sgnArgType.istype(DataType.UBYTE) || sgnArgType.istype(DataType.UWORD))
+                printWarning("sgn() of unsigned type is always 0 or 1, this is perhaps not what was intended", functionCall.args.first().position)
+        }
+
         super.visit(functionCall)
     }
 
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 3fab45f78..c146d23a5 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -2,6 +2,9 @@
 TODO
 ====
 
+- remove statements after an exit() or return
+- fix warnings about that unreachable code?
+
 - option to load library files from a directory instead of the embedded ones
 
 
diff --git a/examples/arithmetic/sgn.p8 b/examples/arithmetic/sgn.p8
new file mode 100644
index 000000000..3361dc7a0
--- /dev/null
+++ b/examples/arithmetic/sgn.p8
@@ -0,0 +1,130 @@
+%import c64flt
+%zeropage basicsafe
+
+main {
+
+    sub start() {
+        byte b1
+        byte b2
+        ubyte ub1
+        ubyte ub2
+        word w1
+        word w2
+        uword uw1
+        uword uw2
+        float f1
+        float f2
+
+        b1 = 10
+        b2 = 10
+        if sgn(b2-b1) != 0
+            c64scr.print("sgn1 error1\n")
+
+        b1 = -100
+        b2 = -100
+        if sgn(b2-b1) != 0
+            c64scr.print("sgn1 error2\n")
+
+        ub1 = 200
+        ub2 = 200
+        if sgn(ub2-ub1) != 0
+            c64scr.print("sgn1 error3\n")
+
+        w1 = 100
+        w2 = 100
+        if sgn(w2-w1) != 0
+            c64scr.print("sgn1 error4\n")
+
+        w1 = -2000
+        w2 = -2000
+        if sgn(w2-w1) != 0
+            c64scr.print("sgn1 error5\n")
+
+        uw1 = 999
+        uw2 = 999
+        if sgn(uw2-uw1) != 0
+            c64scr.print("sgn1 error6\n")
+
+        f1 = 3.45
+        f2 = 3.45
+        if sgn(f2-f1) != 0
+            c64scr.print("sgn1 error7\n")
+
+
+        ; -1
+        b1 = 11
+        b2 = 10
+        if sgn(b2-b1) != -1
+            c64scr.print("sgn2 error1\n")
+
+        b1 = -10
+        b2 = -100
+        if sgn(b2-b1) != -1
+            c64scr.print("sgn2 error2\n")
+
+        ub1 = 202
+        ub2 = 200
+        if sgn(ub2 as byte - ub1 as byte) != -1
+            c64scr.print("sgn2 error3\n")
+
+        w1 = 101
+        w2 = 100
+        if sgn(w2-w1) != -1
+            c64scr.print("sgn2 error4\n")
+
+        w1 = -200
+        w2 = -2000
+        if sgn(w2-w1) != -1
+            c64scr.print("sgn2 error5\n")
+
+        uw1 = 2222
+        uw2 = 999
+        if sgn(uw2 as word - uw1 as word) != -1
+            c64scr.print("sgn2 error6\n")
+        if sgn(uw2 - uw1) != -1
+            c64scr.print("sgn2 error6\n")
+
+        f1 = 3.45
+        f2 = 1.11
+        if sgn(f2-f1) != -1
+            c64scr.print("sgn2 error7\n")
+
+        ; +1
+        b1 = 11
+        b2 = 20
+        if sgn(b2-b1) != 1
+            c64scr.print("sgn3 error1\n")
+
+        b1 = -10
+        b2 = -1
+        if sgn(b2-b1) != 1
+            c64scr.print("sgn3 error2\n")
+
+        ub1 = 202
+        ub2 = 205
+        if sgn(ub2-ub1) != 1
+            c64scr.print("sgn3 error3\n")
+
+        w1 = 101
+        w2 = 200
+        if sgn(w2-w1) != 1
+            c64scr.print("sgn3 error4\n")
+
+        w1 = -200
+        w2 = -20
+        if sgn(w2-w1) != 1
+            c64scr.print("sgn3 error5\n")
+
+        uw1 = 2222
+        uw2 = 9999
+        if sgn(uw2-uw1) != 1
+            c64scr.print("sgn3 error6\n")
+
+        f1 = 3.45
+        f2 = 5.11
+        if sgn(f2-f1) != 1
+            c64scr.print("sgn3 error7\n")
+
+        c64scr.print("should see no sgn errors\n")
+    }
+ }
diff --git a/examples/lines_circles.p8 b/examples/lines-circles.p8
similarity index 90%
rename from examples/lines_circles.p8
rename to examples/lines-circles.p8
index 4b50144bb..28e05c718 100644
--- a/examples/lines_circles.p8
+++ b/examples/lines-circles.p8
@@ -14,6 +14,11 @@ main {
         for r in 3 to 12 step 3 {
             circle(r)
         }
+        line(5,3, 30,3)
+        line(5,3, 5, 24)
+        line(30,3,30,24)
+        line(5,24,30,24)
+
         line(1, 10, 38, 24)
         line(1, 20, 38, 2)
         line(20, 4, 10, 24)
@@ -27,23 +32,11 @@ main {
             ubyte dy = abs(y2 - y1)
             ubyte dx2 = 2 * dx
             ubyte dy2 = 2 * dy
-            byte ix = sgn(x2-x1)
-            byte iy = sgn(y2-y1)
+            byte ix = sgn(x2 as byte - x1 as byte)
+            byte iy = sgn(y2 as byte - y1 as byte)
             ubyte x = x1
             ubyte y = y1
 
-            ; TODO fix sgn
-            if x1<x2
-                ix=1
-            else
-                ix=-1
-
-            ; TODO fix sgn
-            if y1<y2
-                iy=1
-            else
-                iy=-1
-
             if dx >= dy {
                 ; TODO fix assembler problem when defining label here
                 forever {
diff --git a/examples/test.p8 b/examples/test.p8
index a8a43e714..a677335ae 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -1,4 +1,3 @@
-%import c64flt
 %zeropage basicsafe
 
 main {