z80a: add stuctured flow words

Allow us to rely a little less on labels. We now only need 4.

forth/boot.fs

@@ -159,7 +159,7 @@ PC ORG @ 4 + ! ( find )
   adjust. Because the compare loop pre-decrements, instead
   of DECing HL twice, we DEC it once. )
     HL DECss,
-L3 BSET ( inner )
+BEGIN, ( inner )
     ( DE is a wordref, first step, do our len correspond? )
     HL PUSHqq,          ( --> lvl 1 )
     DE PUSHqq,          ( --> lvl 2 )
@@ -172,15 +172,15 @@ L3 BSET ( inner )
     DE DECss, ( Skip prev field. One less because we )
     DE DECss, ( pre-decrement )
     B C LDrr, ( loop C times )
-L5 BSET ( loop )
+BEGIN, ( loop )
     ( pre-decrement for easier Z matching )
     DE DECss,
     HL DECss,
     LDA(DE),
     (HL) CPr,
-    JRNZ, L6 FWR ( loopend )
+    JRNZ, L3 FWR ( loopend )
-    DJNZ, L5 BWR ( loop )
+    DJNZ, AGAIN, ( loop )
-L4 FSET L6 FSET ( loopend )
+L4 FSET L3 FSET ( loopend )
 ( At this point, Z is set if we have a match. In all cases,
   we want to pop HL and DE )
     DE POPqq,           ( <-- lvl 2 )
@@ -201,14 +201,14 @@ L4 FSET L6 FSET ( loopend )
     ( HL is prev field's addr. Is offset zero? )
     A D LDrr,
     E ORr,
-    JRZ, L6 FWR ( noprev )
+    IFZ, ( noprev )
         ( get absolute addr from offset )
         ( carry cleared from "or e" )
         DE SBCHLss,
         EXDEHL,             ( result in DE )
-L6 FSET ( noprev )
+    THEN, ( noprev )
     HL POPqq,           ( <-- lvl 1 )
-    JRNZ, L3 BWR ( inner, try to match again )
+    JRNZ, AGAIN, ( inner, try to match again )
     ( Z set? end of dict, unset Z )
 L1 FSET ( fail )
     A XORr,

forth/z80a.fs

@@ -16,18 +16,16 @@
 
   To avoid using dict memory in compilation targets, we
   pre-declare label variables here, which means we have a
-  limited number of it. For now, 6 ought to be enough. )
+  limited number of it. For now, 4 ought to be enough. )
 : L1 2 Z80AMEM+ ;
 : L2 4 Z80AMEM+ ;
 : L3 6 Z80AMEM+ ;
 : L4 8 Z80AMEM+ ;
-: L5 10 Z80AMEM+ ;
-: L6 12 Z80AMEM+ ;
 
 : Z80A$
     ( 59 == z80a's memory )
     H@ 0x59 RAM+ !
-    14 ALLOT
+    10 ALLOT
 ;
 
 ( Splits word into msb/lsb, lsb being on TOS )
@@ -43,42 +41,6 @@
 : A, C, ;
 : A,, SPLITB A, A, ;
 
-( There are 2 label types: backward and forward. For each
-  type, there are two actions: set and write. Setting a label
-  is declaring where it is. It has to be performed at the
-  label's destination. Writing a label is writing its offset
-  difference to the binary result. It has to be done right
-  after a relative jump operation. Yes, labels are only for
-  relative jumps.
-
-  For backward labels, set happens before write. For forward
-  labels, write happen before set. The write operation writes
-  a dummy placeholder, and then the set operation writes the
-  offset at that placeholder's address.
-
-  Variable actions are expected to be called with labels in
-  front of them. Example, "L2 FSET"
-
-  About that "1 -": z80 relative jumps record "e-2", that is,
-  the offset that *counts the 2 bytes of the jump itself*.
-  Because we set the label *after* the jump OP1 itself, that's
-  1 byte that is taken care of. We still need to adjust by
-  another byte before writing the offset.
-)
-
-: BSET PC SWAP ! ;
-: BWR @ PC - 1 - A, ;
-( same as BSET, but we need to write a placeholder )
-: FWR BSET 0 A, ;
-: FSET
-    @ DUP PC        ( l l pc )
-    -^ 1 -          ( l off )
-    ( warning: l is a PC offset, not a mem addr! )
-    SWAP ORG @ +    ( off addr )
-    C!
-;
-
-
 ( "r" register constants )
 7 CONSTANT A
 0 CONSTANT B
@@ -375,3 +337,52 @@
 ( Routines )
 ( 29 == chkPS )
 : chkPS, 29 CALLnn, ;
+
+( Flow
+
+  There are 2 label types: backward and forward. For each
+  type, there are two actions: set and write. Setting a label
+  is declaring where it is. It has to be performed at the
+  label's destination. Writing a label is writing its offset
+  difference to the binary result. It has to be done right
+  after a relative jump operation. Yes, labels are only for
+  relative jumps.
+
+  For backward labels, set happens before write. For forward
+  labels, write happen before set. The write operation writes
+  a dummy placeholder, and then the set operation writes the
+  offset at that placeholder's address.
+
+  Variable actions are expected to be called with labels in
+  front of them. Example, "L2 FSET"
+
+  About that "1 -": z80 relative jumps record "e-2", that is,
+  the offset that *counts the 2 bytes of the jump itself*.
+  Because we set the label *after* the jump OP1 itself, that's
+  1 byte that is taken care of. We still need to adjust by
+  another byte before writing the offset.
+)
+
+( Place BEGIN, where you want to jump back and AGAIN after
+  a relative jump operator. Just like BSET and BWR. )
+: BEGIN, PC ;
+: AGAIN, PC - 1 - A, ;
+
+: BSET PC SWAP ! ;
+: BWR @ AGAIN, ;
+( same as BSET, but we need to write a placeholder )
+: FJR, PC 0 A, ;
+: IFZ, JRZ, FJR, ;
+: IFNZ, JRNZ, FJR, ;
+: IFC, JRC, FJR, ;
+: IFNC, JRNC, FJR, ;
+: THEN,
+    DUP PC          ( l l pc )
+    -^ 1 -          ( l off )
+    ( warning: l is a PC offset, not a mem addr! )
+    SWAP ORG @ +    ( off addr )
+    C!
+;
+: FWR BSET 0 A, ;
+: FSET @ THEN, ;
+

forth/z80c.fs

@@ -149,10 +149,10 @@ CODE NOT
     A L LDrr,
     H ORr,
     HL 0 LDddnn,
-    JRNZ, L1 FWR ( skip )
+    IFNZ, ( skip )
         ( false, make 1 )
         HL INCss,
-L1 FSET ( skip )
+    THEN, ( skip )
     HL PUSHqq,
 ;CODE
 
@@ -203,17 +203,17 @@ CODE /MOD
     A B LDrr,
     B 16 LDrn,
     HL 0 LDddnn,
-L1 BSET ( loop )
+    BEGIN, ( loop )
         SCF,
         C RLr,
         RLA,
         HL ADCHLss,
         DE SBCHLss,
-    JRNC, L2 FWR ( skip )
+        IFNC, ( skip )
             DE ADDHLss,
             C DECr,
-L2 FSET ( skip )
+        THEN, ( skip )
-    DJNZ, L1 BWR ( loop )
+    DJNZ, AGAIN, ( loop )
     B A LDrr,
     HL PUSHqq,
     BC PUSHqq,
@@ -315,16 +315,16 @@ CODE SCMP
     DE  POPqq,
     HL  POPqq,
     chkPS,
-L1 BSET ( loop )
+    BEGIN, ( loop )
         LDA(DE),
         (HL) CPr,
-    JRNZ, L2 FWR ( not equal? break early to "end".
+        JRNZ, L1 FWR ( not equal? break early to "end".
                        NZ is set. )
         A ORr,   ( if our char is null, stop )
         HL INCss,
         DE INCss,
-    JRNZ, L1 BWR ( loop )
+    JRNZ, AGAIN, ( loop )
-L2 FSET ( end )
+L1 FSET ( end )
     ( 40 == flagsToBC )
     40 CALLnn,
     BC PUSHqq,
@@ -347,13 +347,13 @@ CODE _find
     chkPS,
     ( 3 == find )
     3 CALLnn,
-    JRZ, L1 FWR ( found )
+    IFZ, ( found )
         ( not found )
         HL PUSHqq,
         DE 0 LDddnn,
         DE PUSHqq,
         JPNEXT,
-L1 FSET ( found )
+    THEN, ( found )
     DE PUSHqq,
     DE 1 LDddnn,
     DE PUSHqq,