diff --git a/compiler/res/prog8lib/string.p8 b/compiler/res/prog8lib/string.p8
index ff4054fd0..1d21bf9b6 100644
--- a/compiler/res/prog8lib/string.p8
+++ b/compiler/res/prog8lib/string.p8
@@ -129,7 +129,7 @@ _startloop	dey
 
     asmsub find(uword string @R0, ubyte character @A) -> ubyte @A, ubyte @Pc {
         ; Locates the first position of the given character in the string,
-        ; returns Carry set if found + index in A, or Carry clear if not found.
+        ; returns Carry set if found + index in A, or A=0 + Carry clear if not found.
         %asm {{
                 ; need to copy the the cx16 virtual registers to zeropage to make this run on C64...
                 sta  P8ZP_SCRATCH_B1
@@ -144,7 +144,8 @@ _startloop	dey
 		beq  _found
 		iny
 		bne  -
-_notfound	clc
+_notfound	lda  #0
+                clc
 		rts
 _found		tya
                 sec
diff --git a/compiler/src/prog8/CompilerMain.kt b/compiler/src/prog8/CompilerMain.kt
index e5ce4c711..4aa07c3cd 100644
--- a/compiler/src/prog8/CompilerMain.kt
+++ b/compiler/src/prog8/CompilerMain.kt
@@ -10,10 +10,7 @@ import prog8.compiler.CompilationResult
 import prog8.compiler.CompilerArguments
 import prog8.compiler.compileProgram
 import java.io.File
-import java.nio.file.FileSystems
-import java.nio.file.Path
-import java.nio.file.Paths
-import java.nio.file.StandardWatchEventKinds
+import java.nio.file.*
 import java.time.LocalDateTime
 import kotlin.system.exitProcess
 
@@ -148,16 +145,26 @@ private fun compileMain(args: Array<String>): Boolean {
             }
             println("[${LocalDateTime.now().withNano(0)}]  Waiting for file changes.")
 
+            fun determineRecompilationNeeded(event: WatchKey): Boolean {
+                if(event.isValid) {
+                    for (changed in event.pollEvents()) {
+                        if (changed.kind() == StandardWatchEventKinds.ENTRY_MODIFY) {
+                            val changedPath = changed.context() as Path
+                            if (allImportedFiles.any { it.fileName == changedPath.fileName }) {
+                                println("  change detected: $changedPath")
+                                return true
+                            }
+                        }
+                    }
+                }
+                return false
+            }
+
             var recompile=false
             while(!recompile) {
                 val event = watchservice.take()
-                for (changed in event.pollEvents()) {
-                    val changedPath = changed.context() as Path
-                    if(allImportedFiles.any { it.fileName == changedPath.fileName }) {
-                        println("  change detected: $changedPath")
-                        recompile = true
-                    }
-                }
+                Thread.sleep(50)    // avoid multiple events on same file
+                recompile = determineRecompilationNeeded(event)
                 event.reset()
             }
 
diff --git a/compiler/test/TestCompilerOnExamples.kt b/compiler/test/TestCompilerOnExamples.kt
index a484ad48f..39ba9c4d6 100644
--- a/compiler/test/TestCompilerOnExamples.kt
+++ b/compiler/test/TestCompilerOnExamples.kt
@@ -127,6 +127,7 @@ class TestCompilerOnExamplesBothC64andCx16: FunSpec({
         listOf(
             "animals",
             "balls",
+            "bsieve",
             "cube3d",
             "cube3d-float",
             "cube3d-gfx",
diff --git a/docs/source/libraries.rst b/docs/source/libraries.rst
index 2cacd156e..b30232eda 100644
--- a/docs/source/libraries.rst
+++ b/docs/source/libraries.rst
@@ -172,7 +172,7 @@ Provides string manipulation routines.
 
 ``find(string, char) -> ubyte index + carry bit``
     Locates the first position of the given character in the string, returns carry bit set if found
-    and the index in the string. Or carry bit clear if the character was not found.
+    and the index in the string. Or 0+carry bit clear if the character was not found.
 
 ``compare(string1, string2) -> ubyte result``
     Returns -1, 0 or 1 depeding on wether string1 sorts before, equal or after string2.
diff --git a/docs/source/todo.rst b/docs/source/todo.rst
index 3d2c81fe2..1304b194f 100644
--- a/docs/source/todo.rst
+++ b/docs/source/todo.rst
@@ -3,6 +3,8 @@ TODO
 
 For next release
 ^^^^^^^^^^^^^^^^
+- can we optimize logical expresions such as  if input_size and command_line[0]!=159 to not use stack eval anymore?
+
 ...
 
 
diff --git a/examples/bsieve.p8 b/examples/bsieve.p8
new file mode 100644
index 000000000..14665c5d3
--- /dev/null
+++ b/examples/bsieve.p8
@@ -0,0 +1,51 @@
+%import textio
+%import floats
+%zeropage basicsafe
+%option no_sysinit
+
+; The "Byte Sieve" test.  https://en.wikipedia.org/wiki/Byte_Sieve
+; Note: this program is compatible with C64 and CX16.
+
+main {
+    sub start() {
+
+        c64.SETTIM(0, 0, 0)
+
+        const ubyte ITERS = 10
+        uword count
+        uword i
+        uword prime
+        uword k
+        const uword SIZEPL = 8191
+        uword flags_ptr = memory("flags", SIZEPL, $100)
+
+        txt.print("calculating...\n")
+
+        repeat ITERS {
+            sys.memset(flags_ptr, SIZEPL, 1)
+            count = 0
+            for i in 0 to SIZEPL-1 {
+                if @(flags_ptr+i) {
+                    prime = i + i + 3
+                    k = i + prime
+                    while k <= SIZEPL-1 {
+                        @(flags_ptr + k) = false
+                        k += prime
+                    }
+;                    txt.print_uw(prime)
+;                    txt.spc()
+                    count++
+                }
+            }
+        }
+
+        txt.print_uw(count)
+        txt.print(" primes\n")
+
+        float time = c64.RDTIM16() / 60.0
+        floats.print_f(time)
+        txt.print(" sec total = ")
+        floats.print_f(time/ITERS)
+        txt.print(" sec per iteration\n")
+    }
+}