diff --git a/asm/z80.fnl b/asm/z80.fnl
index 028522c..e531f1b 100644
--- a/asm/z80.fnl
+++ b/asm/z80.fnl
@@ -39,13 +39,6 @@
 (fn opform [opcode matchers prefixgen]
   (chain-op opcode #(try-parse-op $1 matchers prefixgen)))
 
-(fn is-addr? [param] (= (type param) :string))
-(fn addr [param] (when (is-addr? param) {:addr param}))
-(fn rel-addr [param] (when (is-addr? param) {:rel8 param}))
-(fn num [param] (when (= (type param) :number) {:num param}))
-(fn imm16 [param] (when (= (type param) :number) {:imm16 param}))
-(fn imm8 [param] (when (= (type param) :number) {:imm8 param}))
-
 (fn table-matcher [tbl key]
   (let [lookup (collect [i val (ipairs tbl)] val (- i 1))]
     (fn [param] (case (. lookup param) octet {key octet}))))
@@ -55,6 +48,18 @@
                         #(when (argmatch [:hl] $1) {:reg 6})))
 (local rp (table-matcher [:bc :de :hl :sp] :rp))
 (local rp2 (table-matcher [:bc :de :hl :af] :rp))
+
+(fn is-addr? [param] (and (= (type param) :string)
+                          (not= param :ix) (not= param :iy)
+                          (= (reg param) nil) (= (rp param) nil) (= (rp2 param) nil)))
+(fn is-computed? [param] (= (type param) :function))
+(fn is-number? [param] (= (type param) :number))
+(fn rel-addr [param] (when (is-addr? param) {:rel8 param}))
+(fn num [param] (when (or (is-number? param) (is-computed? param)) {:num param}))
+(fn imm16 [param] (when (or (is-number? param) (is-computed? param) (is-addr? param)) {:imm16 param}))
+(fn imm8 [param] (when (or (is-number? param) (is-computed? param)) {:imm8 param}))
+(local addr imm16)
+
 (fn im [arg] (match arg
                 0 {:im 0}
                 1 {:im 2}
@@ -167,7 +172,7 @@
 ; ED prefix
 (opform :in [reg [:c]] #(when (not= $1.reg 6) (.. "\xed" (xyz 1 $1.reg 0))))
 (opform :in [[:c]] #(.. "\xed" (xyz 1 6 0)))
-(opform :out [reg [:c]] #(when (not= $1.reg 6) (.. "\xed" (xyz 1 $1.reg 1))))
+(opform :out [[:c] reg] #(when (not= $1.reg 6) (.. "\xed" (xyz 1 $1.reg 1))))
 (opform :out [[:c]] #(.. "\xed" (xyz 1 6 1)))
 (opform :sbc [:hl rp] #(.. "\xed" (xpqz 1 $1.rp 0 2)))
 (opform :adc [:hl rp] #(.. "\xed" (xpqz 1 $1.rp 1 2)))
@@ -222,19 +227,23 @@
 (fn op-pdat.size [op env]
   (+ (length op.prefix)
      (case op
-       {: addr}  2
        {: rel8}  1
        {: imm16} 2
        {: imm8}  1
        _         0)))
 
+(fn decode-number [param env]
+  (case (type param)
+    :number param
+    :string (env:lookup-addr param)
+    :function (param (setmetatable {} {:__index #(env:lookup-addr $2)}) env)))
+
 (fn op-pdat.bytes [op env]
   (.. op.prefix
       (case op
-        {: addr}  (int16-to-bytes (env:lookup-addr addr))
-        {: rel8}  (int8-to-bytes (- (env:lookup-addr rel8) op.addr))
-        {: imm16} (int16-to-bytes imm16)
-        {: imm8}  (int8-to-bytes imm8)
+        {: rel8}  (int8-to-bytes (- (env:lookup-addr rel8) (+ op.addr 2)))
+        {: imm16} (int16-to-bytes (decode-number imm16 env))
+        {: imm8}  (int8-to-bytes (decode-number imm8 env))
         _         "")))
 
 {: opcodes : parse-op : op-pdat : try-parse-op}