diff --git a/compiler/src/prog8/functions/BuiltinFunctions.kt b/compiler/src/prog8/functions/BuiltinFunctions.kt
index 0f00ac894..97e097c3a 100644
--- a/compiler/src/prog8/functions/BuiltinFunctions.kt
+++ b/compiler/src/prog8/functions/BuiltinFunctions.kt
@@ -34,7 +34,6 @@ val BuiltinFunctions = mapOf(
     "atan"        to FunctionSignature(true, listOf(BuiltinFunctionParam("rads", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::atan) },
     "ln"          to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::log) },
     "log2"        to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, ::log2) },
-    "log10"       to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::log10) },
     "sqrt"        to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::sqrt) },
     "rad"         to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::toRadians) },
     "deg"         to FunctionSignature(true, listOf(BuiltinFunctionParam("value", setOf(DataType.FLOAT))), DataType.FLOAT) { a, p, n, h -> oneDoubleArg(a, p, n, h, Math::toDegrees) },
diff --git a/compiler/src/prog8/stackvm/StackVm.kt b/compiler/src/prog8/stackvm/StackVm.kt
index 9109cb585..521a42a9b 100644
--- a/compiler/src/prog8/stackvm/StackVm.kt
+++ b/compiler/src/prog8/stackvm/StackVm.kt
@@ -33,7 +33,6 @@ enum class Syscall(val callNr: Short) {
     FUNC_ATAN(72),
     FUNC_LN(73),
     FUNC_LOG2(74),
-    FUNC_LOG10(75),
     FUNC_SQRT(76),
     FUNC_RAD(77),
     FUNC_DEG(78),
@@ -1513,7 +1512,6 @@ class StackVm(private var traceOutputFile: String?) {
             Syscall.FUNC_ATAN -> evalstack.push(Value(DataType.FLOAT, atan(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_LN -> evalstack.push(Value(DataType.FLOAT, ln(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_LOG2 -> evalstack.push(Value(DataType.FLOAT, log2(evalstack.pop().numericValue().toDouble())))
-            Syscall.FUNC_LOG10 -> evalstack.push(Value(DataType.FLOAT, log10(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_SQRT -> evalstack.push(Value(DataType.FLOAT, sqrt(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_RAD -> evalstack.push(Value(DataType.FLOAT, Math.toRadians(evalstack.pop().numericValue().toDouble())))
             Syscall.FUNC_DEG -> evalstack.push(Value(DataType.FLOAT, Math.toDegrees(evalstack.pop().numericValue().toDouble())))
diff --git a/docs/source/programming.rst b/docs/source/programming.rst
index 4984830b7..11c1f8487 100644
--- a/docs/source/programming.rst
+++ b/docs/source/programming.rst
@@ -502,14 +502,11 @@ atan(x)
 	Arctangent.
 
 ln(x)
-	Natural logarithm (base E).
+	Natural logarithm (base e).
 
 log2(x)
     Base 2 logarithm.
 
-log10(x)
-	Base 10 logarithm.
-
 sqrt(x)
 	Square root.
 
diff --git a/prog8lib/prog8lib.p8 b/prog8lib/prog8lib.p8
index 86c7f772a..5d57b666e 100644
--- a/prog8lib/prog8lib.p8
+++ b/prog8lib/prog8lib.p8
@@ -861,23 +861,32 @@ func_tan	.proc
 		.pend
 		
 func_atan	.proc
-		rts
-		.warn "atan not implemented"
+		; -- push atan(f) back onto stack
+		jsr  pop_float_fac1
+		stx  SCRATCH_ZPREGX
+		jsr  c64.ATN
+		jmp  push_fac1_as_result
 		.pend
 		
 func_ln		.proc
-		rts
-		.warn "ln not implemented"
+		; -- push ln(f) back onto stack
+		jsr  pop_float_fac1
+		stx  SCRATCH_ZPREGX
+		jsr  c64.LOG
+		jmp  push_fac1_as_result
 		.pend
 		
 func_log2	.proc
-		rts
-		.warn "log2 not implemented"
-		.pend
-		
-func_log10	.proc
-		rts
-		.warn "log10 not implemented"
+		; -- push log base 2, ln(f)/ln(2), back onto stack
+		jsr  pop_float_fac1
+		stx  SCRATCH_ZPREGX
+		jsr  c64.LOG
+		jsr  c64.MOVEF
+		lda  #<c64.FL_LOG2
+		ldy  #>c64.FL_LOG2
+		jsr  c64.MOVFM
+		jsr  c64.FDIVT
+		jmp  push_fac1_as_result
 		.pend
 		
 func_sqrt	.proc
@@ -909,7 +918,7 @@ func_deg	.proc
 _one_over_pi_div_180	.byte 134, 101, 46, 224, 211		; 1 / (pi * 180)
 		.pend
 		
-func_round	.proc        ; @todo check outcome vs floor/ceil
+func_round	.proc
 		jsr  pop_float_fac1
 		stx  SCRATCH_ZPREGX
 		jsr  c64.FADDH
@@ -920,6 +929,7 @@ func_round	.proc        ; @todo check outcome vs floor/ceil
 		sta  ESTACK_LO,x
 		dex
 		rts
+		.warn  "round check outcome"
 		.pend
 		
 func_floor	.proc        ; @todo check outcome vs round/ceil