diff --git a/codeCore/src/prog8/code/SymbolTableMaker.kt b/codeCore/src/prog8/code/SymbolTableMaker.kt
index 9cd7c168e..6462276ff 100644
--- a/codeCore/src/prog8/code/SymbolTableMaker.kt
+++ b/codeCore/src/prog8/code/SymbolTableMaker.kt
@@ -3,7 +3,8 @@ package prog8.code
 import prog8.code.ast.*
 import prog8.code.core.*
 import prog8.code.target.VMTarget
-import java.util.*
+import kotlin.collections.ArrayDeque
+
 
 class SymbolTableMaker(private val program: PtProgram, private val options: CompilationOptions) {
     fun make(): SymbolTable {
@@ -13,8 +14,8 @@ class SymbolTableMaker(private val program: PtProgram, private val options: Comp
             st.add(StNode(it.key, StNodeType.BUILTINFUNC, PtIdentifier(it.key, it.value.returnType ?: DataType.UNDEFINED, Position.DUMMY)))
         }
 
-        val scopestack = Stack<StNode>()
-        scopestack.push(st)
+        val scopestack = ArrayDeque<StNode>()
+        scopestack.add(st)
         program.children.forEach {
             addToSt(it, scopestack)
         }
@@ -35,7 +36,7 @@ class SymbolTableMaker(private val program: PtProgram, private val options: Comp
         return st
     }
 
-    private fun addToSt(node: PtNode, scope: Stack<StNode>) {
+    private fun addToSt(node: PtNode, scope: ArrayDeque<StNode>) {
         val stNode = when(node) {
             is PtAsmSub -> {
                 val parameters = node.parameters.map { StRomSubParameter(it.first, it.second.type) }
@@ -104,7 +105,7 @@ class SymbolTableMaker(private val program: PtProgram, private val options: Comp
                     val size = (node.args[1] as PtNumber).number.toUInt()
                     val align = (node.args[2] as PtNumber).number.toUInt()
                     // don't add memory slabs in nested scope, just put them in the top level of the ST
-                    scope.firstElement().add(StMemorySlab("prog8_memoryslab_$slabname", size, align, node))
+                    scope.first().add(StMemorySlab("prog8_memoryslab_$slabname", size, align, node))
                 }
                 null
             }
@@ -112,14 +113,14 @@ class SymbolTableMaker(private val program: PtProgram, private val options: Comp
         }
 
         if(stNode!=null) {
-            scope.peek().add(stNode)
-            scope.push(stNode)
+            scope.last().add(stNode)
+            scope.add(stNode)
         }
         node.children.forEach {
             addToSt(it, scope)
         }
         if(stNode!=null)
-            scope.pop()
+            scope.removeLast()
     }
 
     private fun makeInitialArray(value: PtArray): List<StArrayElement> {
diff --git a/codeCore/src/prog8/code/ast/AstExpressions.kt b/codeCore/src/prog8/code/ast/AstExpressions.kt
index 1c11dc2a3..c4e470154 100644
--- a/codeCore/src/prog8/code/ast/AstExpressions.kt
+++ b/codeCore/src/prog8/code/ast/AstExpressions.kt
@@ -1,7 +1,7 @@
 package prog8.code.ast
 
 import prog8.code.core.*
-import java.util.*
+import java.util.Objects
 import kotlin.math.abs
 import kotlin.math.truncate
 
@@ -227,12 +227,6 @@ class PtMemoryByte(position: Position) : PtExpression(DataType.UBYTE, position)
 
 
 class PtBool(val value: Boolean, position: Position) : PtExpression(DataType.BOOL, position) {
-
-    companion object {
-        fun fromNumber(number: Number, position: Position): PtBool =
-            PtBool(number != 0.0, position)
-    }
-
     override fun hashCode(): Int = Objects.hash(type, value)
 
     override fun equals(other: Any?): Boolean {
diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
index 3f93c293d..e79afa364 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/AsmGen.kt
@@ -9,7 +9,7 @@ import prog8.code.ast.*
 import prog8.code.core.*
 import prog8.code.target.Cx16Target
 import prog8.codegen.cpu6502.assignment.*
-import java.util.*
+import kotlin.collections.ArrayDeque
 import kotlin.io.path.Path
 import kotlin.io.path.writeLines
 
@@ -772,7 +772,7 @@ class AsmGen6502Internal (
 
     private fun translate(stmt: PtRepeatLoop) {
         val endLabel = makeLabel("repeatend")
-        loopEndLabels.push(endLabel)
+        loopEndLabels.add(endLabel)
 
         when (stmt.count) {
             is PtNumber -> {
@@ -816,7 +816,7 @@ class AsmGen6502Internal (
             }
         }
 
-        loopEndLabels.pop()
+        loopEndLabels.removeLast()
     }
 
     private fun repeatWordCount(iterations: Int, stmt: PtRepeatLoop) {
diff --git a/codeGenCpu6502/src/prog8/codegen/cpu6502/ForLoopsAsmGen.kt b/codeGenCpu6502/src/prog8/codegen/cpu6502/ForLoopsAsmGen.kt
index 06798d944..d358d0031 100644
--- a/codeGenCpu6502/src/prog8/codegen/cpu6502/ForLoopsAsmGen.kt
+++ b/codeGenCpu6502/src/prog8/codegen/cpu6502/ForLoopsAsmGen.kt
@@ -37,7 +37,7 @@ internal class ForLoopsAsmGen(
         val endLabel = asmgen.makeLabel("for_end")
         val modifiedLabel = asmgen.makeLabel("for_modified")
         val modifiedLabel2 = asmgen.makeLabel("for_modifiedb")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val stepsize=range.step.asConstInteger()!!
 
         if(stepsize < -1) {
@@ -277,7 +277,7 @@ $endLabel""")
             else -> throw AssemblyError("range expression can only be byte or word")
         }
 
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun precheckFromToWord(iterableDt: DataType, stepsize: Int, fromVar: String, endLabel: String) {
@@ -333,7 +333,7 @@ $endLabel""")
     private fun translateForOverIterableVar(stmt: PtForLoop, iterableDt: DataType, ident: PtIdentifier) {
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val iterableName = asmgen.asmVariableName(ident)
         val numElements = when(val symbol = asmgen.symbolTable.lookup(ident.name)) {
             is StStaticVariable -> symbol.length!!
@@ -477,7 +477,7 @@ $loopLabel          sty  $indexVar
             }
             else -> throw AssemblyError("can't iterate over $iterableDt")
         }
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun translateForOverConstRange(stmt: PtForLoop, iterableDt: DataType, range: IntProgression) {
@@ -495,7 +495,7 @@ $loopLabel          sty  $indexVar
         // not one of the easy cases, generate more complex code...
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         when(iterableDt) {
             DataType.ARRAY_B, DataType.ARRAY_UB -> {
                 // loop over byte range via loopvar, step >= 2 or <= -2
@@ -601,13 +601,13 @@ $loopLabel""")
             }
             else -> throw AssemblyError("range expression can only be byte or word")
         }
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun translateForSimpleByteRangeAsc(stmt: PtForLoop, range: IntProgression) {
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val varname = asmgen.asmVariableName(stmt.variable)
         asmgen.out("""
                 lda  #${range.first}
@@ -627,13 +627,13 @@ $endLabel""")
                 bne  $loopLabel
 $endLabel""")
         }
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun translateForSimpleByteRangeDesc(stmt: PtForLoop, range: IntProgression) {
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val varname = asmgen.asmVariableName(stmt.variable)
         asmgen.out("""
                     lda  #${range.first}
@@ -664,13 +664,13 @@ $endLabel""")
 $endLabel""")
             }
         }
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun translateForSimpleWordRangeAsc(stmt: PtForLoop, range: IntProgression) {
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val varname = asmgen.asmVariableName(stmt.variable)
         asmgen.out("""
             lda  #<${range.first}
@@ -691,13 +691,13 @@ $loopLabel""")
             inc  $varname+1""")
         asmgen.jmp(loopLabel)
         asmgen.out(endLabel)
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun translateForSimpleWordRangeDesc(stmt: PtForLoop, range: IntProgression) {
         val loopLabel = asmgen.makeLabel("for_loop")
         val endLabel = asmgen.makeLabel("for_end")
-        asmgen.loopEndLabels.push(endLabel)
+        asmgen.loopEndLabels.add(endLabel)
         val varname = asmgen.asmVariableName(stmt.variable)
         asmgen.out("""
             lda  #<${range.first}
@@ -719,7 +719,7 @@ $loopLabel""")
 +           dec  $varname""")
         asmgen.jmp(loopLabel)
         asmgen.out(endLabel)
-        asmgen.loopEndLabels.pop()
+        asmgen.loopEndLabels.removeLast()
     }
 
     private fun assignLoopvarWord(stmt: PtForLoop, range: PtRange) =
diff --git a/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt b/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
index 4cfbb0689..cb1959d6a 100644
--- a/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
@@ -11,9 +11,9 @@ import prog8.ast.statements.*
 import prog8.code.ast.*
 import prog8.code.core.*
 import prog8.compiler.builtinFunctionReturnType
-import java.io.File
 import kotlin.io.path.Path
 import kotlin.io.path.isRegularFile
+import java.io.File
 
 
 /**
diff --git a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
index 65611f7e8..a5cdc6428 100644
--- a/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
+++ b/compilerAst/src/prog8/ast/expressions/AstExpressions.kt
@@ -12,7 +12,7 @@ import prog8.ast.walk.IAstVisitor
 import prog8.code.core.*
 import prog8.code.target.encodings.JapaneseCharacterConverter
 import java.io.CharConversionException
-import java.util.*
+import java.util.Objects
 import kotlin.math.abs
 import kotlin.math.floor
 import kotlin.math.truncate
diff --git a/compilerAst/src/prog8/ast/expressions/InferredTypes.kt b/compilerAst/src/prog8/ast/expressions/InferredTypes.kt
index 8d0ddbd81..5ae2251b5 100644
--- a/compilerAst/src/prog8/ast/expressions/InferredTypes.kt
+++ b/compilerAst/src/prog8/ast/expressions/InferredTypes.kt
@@ -1,7 +1,7 @@
 package prog8.ast.expressions
 
 import prog8.code.core.*
-import java.util.*
+import java.util.Objects
 
 
 object InferredTypes {
diff --git a/virtualmachine/src/prog8/vm/VirtualMachine.kt b/virtualmachine/src/prog8/vm/VirtualMachine.kt
index 13870251c..ae866f8ca 100644
--- a/virtualmachine/src/prog8/vm/VirtualMachine.kt
+++ b/virtualmachine/src/prog8/vm/VirtualMachine.kt
@@ -6,7 +6,7 @@ import prog8.code.target.virtual.VirtualMachineDefinition
 import prog8.intermediate.*
 import java.awt.Color
 import java.awt.Toolkit
-import java.util.*
+import kotlin.collections.ArrayDeque
 import kotlin.math.*
 import kotlin.random.Random
 
@@ -39,8 +39,8 @@ class VirtualMachine(irProgram: IRProgram) {
     val program: List<IRCodeChunk>
     val artificialLabelAddresses: Map<Int, IRCodeChunk>
     val registers = Registers()
-    val callStack = Stack<CallSiteContext>()
-    val valueStack = Stack<UByte>()       // max 128 entries
+    val callStack = ArrayDeque<CallSiteContext>()
+    val valueStack = ArrayDeque<UByte>()       // max 128 entries
     var breakpointHandler: ((pcChunk: IRCodeChunk, pcIndex: Int) -> Unit)? = null       // can set custom breakpoint handler
     var pcChunk = IRCodeChunk(null, null)
     var pcIndex = 0
@@ -360,7 +360,7 @@ class VirtualMachine(irProgram: IRProgram) {
         when(i.type!!) {
             IRDataType.BYTE -> {
                 val value = registers.getUB(i.reg1!!)
-                valueStack.push(value)
+                valueStack.add(value)
             }
             IRDataType.WORD -> {
                 val value = registers.getUW(i.reg1!!)
@@ -376,7 +376,7 @@ class VirtualMachine(irProgram: IRProgram) {
 
     private fun InsPOP(i: IRInstruction) {
         when(i.type!!) {
-            IRDataType.BYTE -> setResultReg(i.reg1!!, valueStack.pop().toInt(), i.type!!)
+            IRDataType.BYTE -> setResultReg(i.reg1!!, valueStack.removeLast().toInt(), i.type!!)
             IRDataType.WORD -> setResultReg(i.reg1!!, valueStack.popw().toInt(), i.type!!)
             IRDataType.FLOAT -> registers.setFloat(i.fpReg1!!, valueStack.popf())
         }
@@ -392,12 +392,12 @@ class VirtualMachine(irProgram: IRProgram) {
         if(statusCarry)
             status = status or 0b00000001u
         // TODO overflow not yet supported
-        valueStack.push(status)
+        valueStack.add(status)
         nextPc()
     }
 
     private fun InsPOPST() {
-        val status = valueStack.pop().toInt()
+        val status = valueStack.removeLast().toInt()
         statusNegative = status and 0b10000000 != 0
         statusZero = status and 0b00000010 != 0
         statusCarry = status and 0b00000001 != 0
@@ -411,7 +411,7 @@ class VirtualMachine(irProgram: IRProgram) {
             if(value.dt==null)
                 break
             when(value.dt!!) {
-                IRDataType.BYTE -> valueStack.push(value.value as UByte)
+                IRDataType.BYTE -> valueStack.add(value.value as UByte)
                 IRDataType.WORD -> valueStack.pushw(value.value as UShort)
                 IRDataType.FLOAT -> valueStack.pushf(value.value as Double)
             }
@@ -633,7 +633,7 @@ class VirtualMachine(irProgram: IRProgram) {
             }
         }
         // store the call site and jump
-        callStack.push(CallSiteContext(pcChunk, pcIndex+1, i.fcallArgs!!))
+        callStack.add(CallSiteContext(pcChunk, pcIndex+1, i.fcallArgs!!))
         branchTo(i)
     }
 
@@ -641,7 +641,7 @@ class VirtualMachine(irProgram: IRProgram) {
         if(callStack.isEmpty())
             exit(0)
         else {
-            val context = callStack.pop()
+            val context = callStack.removeLast()
             pcChunk = context.returnChunk
             pcIndex = context.returnIndex
             // ignore any return values.
@@ -652,7 +652,7 @@ class VirtualMachine(irProgram: IRProgram) {
         if(callStack.isEmpty())
             exit(0)
         else {
-            val context = callStack.pop()
+            val context = callStack.removeLast()
             val returns = context.fcallSpec.returns
             when (i.type!!) {
                 IRDataType.BYTE -> {
@@ -1487,16 +1487,16 @@ class VirtualMachine(irProgram: IRProgram) {
         val right = registers.getUB(reg2)
         val division = if(right==0.toUByte()) 0xffu else left / right
         val remainder = if(right==0.toUByte()) 0u else left % right
-        valueStack.push(division.toUByte())
-        valueStack.push(remainder.toUByte())
+        valueStack.add(division.toUByte())
+        valueStack.add(remainder.toUByte())
     }
 
     private fun divAndModConstUByte(reg1: Int, value: UByte) {
         val left = registers.getUB(reg1)
         val division = if(value==0.toUByte()) 0xffu else left / value
         val remainder = if(value==0.toUByte()) 0u else left % value
-        valueStack.push(division.toUByte())
-        valueStack.push(remainder.toUByte())
+        valueStack.add(division.toUByte())
+        valueStack.add(remainder.toUByte())
     }
 
     private fun divAndModUWord(reg1: Int, reg2: Int) {
@@ -2491,47 +2491,47 @@ class VirtualMachine(irProgram: IRProgram) {
     }
 }
 
-internal fun Stack<UByte>.pushw(value: UShort) {
-    push((value and 255u).toUByte())
-    push((value.toInt() ushr 8).toUByte())
+internal fun ArrayDeque<UByte>.pushw(value: UShort) {
+    add((value and 255u).toUByte())
+    add((value.toInt() ushr 8).toUByte())
 }
 
-internal fun Stack<UByte>.pushf(value: Double) {
+internal fun ArrayDeque<UByte>.pushf(value: Double) {
     // push float; lsb first, msb last
     var bits = value.toBits()
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
     bits = bits ushr 8
-    push(bits.toUByte())
+    add(bits.toUByte())
 }
 
-internal fun Stack<UByte>.popw(): UShort {
-    val msb = pop()
-    val lsb = pop()
+internal fun ArrayDeque<UByte>.popw(): UShort {
+    val msb = removeLast()
+    val lsb = removeLast()
     return ((msb.toInt() shl 8) + lsb.toInt()).toUShort()
 }
 
-internal fun Stack<UByte>.popf(): Double {
+internal fun ArrayDeque<UByte>.popf(): Double {
     // pop float; lsb is on bottom, msb on top
-    val b0 = pop().toLong()
-    val b1 = pop().toLong()
-    val b2 = pop().toLong()
-    val b3 = pop().toLong()
-    val b4 = pop().toLong()
-    val b5 = pop().toLong()
-    val b6 = pop().toLong()
-    val b7 = pop().toLong()
+    val b0 = removeLast().toLong()
+    val b1 = removeLast().toLong()
+    val b2 = removeLast().toLong()
+    val b3 = removeLast().toLong()
+    val b4 = removeLast().toLong()
+    val b5 = removeLast().toLong()
+    val b6 = removeLast().toLong()
+    val b7 = removeLast().toLong()
     val bits = b7 +
             (1L shl 8)*b6 +
             (1L shl 16)*b5 +