Add 2>R and 2R>

This allows us to make DO..LOOP more compact.

blk/048

@@ -1,7 +1,9 @@
 Return Stack
 
 >R          n -- R:n        Pops PS and push to RS
+2>R         x y -- R:x y    Equivalent to SWAP >R >R
 R>          R:n -- n        Pops RS and push to PS
+2R>         R:x y -- x y    Equivalent to R> R> SWAP
 I           -- n            Copy RS TOS to PS
 I'          -- n            Copy RS second item to PS
 J           -- n            Copy RS third item to PS

blk/326

@@ -1,13 +1,17 @@
 CODE >R
-    HL POPqq,
+    HL POPqq, chkPS,
-    chkPS,
+    17 BCALL, ( 17 == pushRS )
-    ( 17 == pushRS )
+;CODE
-    17 BCALL,
+CODE 2>R
+    DE POPqq, HL POPqq, chkPS,
+    17 BCALL, ( 17 == pushRS ) EXDEHL, 17 BCALL,
 ;CODE
-
 CODE R>
-    ( 20 == popRS )
+    20 BCALL, ( 20 == popRS )
-    20 BCALL,
     HL PUSHqq,
 ;CODE
+CODE 2R>
+    20 BCALL, ( 20 == popRS ) EXDEHL, 20 BCALL,
+    HL PUSHqq, DE PUSHqq,
+;CODE
 

blk/431

@@ -3,11 +3,8 @@
 : / /MOD SWAP DROP ;
 : MOD /MOD DROP ;
 
-( In addition to pushing H@ this compiles 2 >R so that loop
+( In addition to pushing H@ this compiles 2>R so that loop
   variables are sent to PS at runtime )
-: DO
+: DO COMPILE 2>R H@ ; IMMEDIATE
-    COMPILE SWAP COMPILE >R COMPILE >R
-    H@
-; IMMEDIATE
 
 

blk/432

@@ -12,5 +12,5 @@
 : LOOP
     COMPILE _ COMPILE (?br)
     H@ - ,
-    COMPILE R> COMPILE DROP COMPILE R> COMPILE DROP
+    COMPILE 2R> COMPILE 2DROP
 ; IMMEDIATE