basic: aggressively reduce diff between steps

Copy structural changes from high steps to low steps (mostly, split RE
out of REP) in order to reduce the diffs (mostly, 3 to 4 which is
already too large).

On the contrary, remove similar backports that only increase the
complexity of first steps without reducing the diffs:
 * push the environment in the stack in step2 (it does not change yet)
 * release env if not on top of the stack in step3 (not TCO yet)
 * ignoring metadata in steps4-9 (no metadata yet)

Remove obsolete debug assignments from the start of DO_FUNCTION in
step2.

Reorder the load-file logic in steps6-A in order to reduce the diff
between steps 9 and A.

Aggressively remove differences in spaces and comments.

impls/basic/step0_repl.in.bas

@@ -1,38 +1,34 @@
 GOTO MAIN
 
+REM $INCLUDE: 'mem.in.bas'
 REM $INCLUDE: 'readline.in.bas'
 
 REM $INCLUDE: 'debug.in.bas'
 
-REM READ(A$) -> R$
-MAL_READ:
-  R$=A$
-  RETURN
+REM READ is inlined in RE
 
-REM EVAL(A$, E) -> R$
-EVAL:
+REM EVAL(A$) -> R$
+SUB EVAL
   R$=A$
-  RETURN
+END SUB
 
-REM PRINT(A$) -> R$
-MAL_PRINT:
-  R$=A$
-  RETURN
+REM PRINT is inlined in REP
 
 REM REP(A$) -> R$
-REP:
-  GOSUB MAL_READ
-  A=R:GOSUB EVAL
-  A=R:GOSUB MAL_PRINT
-  RETURN
+SUB REP
+  REM inlined READ (not affecting A$)
+  CALL EVAL
+  REM inlined PRINT (not affecting A$)
+END SUB
 
 REM MAIN program
 MAIN:
   REPL_LOOP:
     A$="user> ":GOSUB READLINE: REM call input parser
     IF EZ=1 THEN GOTO QUIT
+    IF R$="" THEN GOTO REPL_LOOP
 
-    A$=R$:GOSUB REP: REM call REP
+    A$=R$:CALL REP
 
     PRINT R$
     GOTO REPL_LOOP
@@ -41,4 +37,3 @@ MAIN:
     REM GOSUB PR_MEMORY_SUMMARY_SMALL
     #cbm END
     #qbasic SYSTEM
-

impls/basic/step1_read_print.in.bas

@@ -8,34 +8,41 @@ REM $INCLUDE: 'printer.in.bas'
 
 REM $INCLUDE: 'debug.in.bas'
 
-REM READ(A$) -> R
-MAL_READ:
-  GOSUB READ_STR
-  RETURN
+REM READ is inlined in RE
 
-REM EVAL(A, E) -> R
+REM EVAL(A) -> R
 SUB EVAL
   R=A
 END SUB
 
-REM PRINT(A) -> R$
-MAL_PRINT:
-  AZ=A:B=1:GOSUB PR_STR
-  RETURN
+REM PRINT is inlined in REP
+
+REM RE(A$) -> R
+REM caller must release result
+RE:
+  R1=-1
+  GOSUB READ_STR: REM inlined READ
+  R1=R
+  IF ER<>-2 THEN GOTO RE_DONE
+
+  A=R:CALL EVAL
+
+  RE_DONE:
+    RETURN: REM caller must release result of EVAL
 
 REM REP(A$) -> R$
 SUB REP
-  GOSUB MAL_READ
-  IF ER<>-2 THEN GOTO REP_DONE
+  R2=-1
 
-  A=R:CALL EVAL
+  GOSUB RE
+  R2=R
   IF ER<>-2 THEN GOTO REP_DONE
 
-  A=R:GOSUB MAL_PRINT
+  AZ=R:B=1:GOSUB PR_STR: REM inlined PRINT
 
   REP_DONE:
     REM Release memory from EVAL
-    AY=R:GOSUB RELEASE
+    AY=R2:GOSUB RELEASE
 END SUB
 
 REM MAIN program
@@ -49,19 +56,22 @@ MAIN:
     IF EZ=1 THEN GOTO QUIT
     IF R$="" THEN GOTO REPL_LOOP
 
-    A$=R$:CALL REP: REM call REP
+    A$=R$:CALL REP
 
     IF ER<>-2 THEN GOSUB PRINT_ERROR:GOTO REPL_LOOP
     PRINT R$
     GOTO REPL_LOOP
 
   QUIT:
     REM GOSUB PR_MEMORY_SUMMARY_SMALL
+    REM GOSUB PR_MEMORY_MAP
+    REM P1=0:P2=ZI:GOSUB PR_MEMORY
+    REM P1=D:GOSUB PR_OBJECT
+    REM P1=ZK:GOSUB PR_OBJECT
     #cbm END
     #qbasic SYSTEM
 
   PRINT_ERROR:
     PRINT "Error: "+E$
     ER=-2:E$=""
     RETURN
-

impls/basic/step2_eval.in.bas

@@ -12,8 +12,7 @@ REM READ is inlined in RE
 
 REM EVAL_AST(A, E) -> R
 SUB EVAL_AST
-  REM push A and E on the stack
-  Q=E:GOSUB PUSH_Q
+  REM push A on the stack
   GOSUB PUSH_A
 
   IF ER<>-2 THEN GOTO EVAL_AST_RETURN
@@ -46,7 +45,6 @@ SUB EVAL_AST
       REM release it below)
       IF T=8 THEN N=M:M=Z%(A+2):Z%(M)=Z%(M)+32
 
-
       REM update the return sequence structure
       REM release N (and M if T=8) since seq takes full ownership
       C=1:GOSUB MAP_LOOP_UPDATE
@@ -61,17 +59,15 @@ SUB EVAL_AST
       GOTO EVAL_AST_RETURN
 
   EVAL_AST_RETURN:
-    REM pop A and E off the stack
+    REM pop A off the stack
     GOSUB POP_A
-    GOSUB POP_Q:E=Q
 END SUB
 
 REM EVAL(A, E) -> R
 SUB EVAL
   LV=LV+1: REM track basic return stack level
 
-  REM push A and E on the stack
-  Q=E:GOSUB PUSH_Q
+  REM push A on the stack
   GOSUB PUSH_A
 
   REM PRINT "EVAL A:"+STR$(A)+",X:"+STR$(X)+",LV:"+STR$(LV)+",FRE:"+STR$(FRE(0))
@@ -117,8 +113,6 @@ SUB EVAL
       F=Z%(R+2)
 
       GOSUB TYPE_F
-
-      REM ON .. GOTO here reduces the diff with later steps.
       T=T-8
       IF 0<T THEN ON T GOTO EVAL_DO_FUNCTION
 
@@ -147,19 +141,13 @@ SUB EVAL
     #cbm T=FRE(0)
     #qbasic T=0
 
-    REM pop A and E off the stack
+    REM pop A off the stack
     GOSUB POP_A
-    GOSUB POP_Q:E=Q
 
 END SUB
 
 REM DO_FUNCTION(F, AR)
 DO_FUNCTION:
-  AZ=F:GOSUB PR_STR
-  F$=R$
-  AZ=AR:GOSUB PR_STR
-  AR$=R$
-
   REM Get the function number
   G=Z%(F+1)
 
@@ -192,24 +180,36 @@ DO_FUNCTION:
 
 REM PRINT is inlined in REP
 
-REM REP(A$) -> R$
+REM RE(A$) -> R
 REM Assume D has repl_env
-SUB REP
+REM caller must release result
+RE:
   R1=-1
-  GOSUB READ_STR: REM inlined MAL_READ
+  GOSUB READ_STR: REM inlined READ
   R1=R
-  IF ER<>-2 THEN GOTO REP_DONE
+  IF ER<>-2 THEN GOTO RE_DONE
 
   A=R:E=D:CALL EVAL
+
+  RE_DONE:
+    REM Release memory from READ
+    AY=R1:GOSUB RELEASE
+    RETURN: REM caller must release result of EVAL
+
+REM REP(A$) -> R$
+REM Assume D has repl_env
+SUB REP
+  R2=-1
+
+  GOSUB RE
   R2=R
   IF ER<>-2 THEN GOTO REP_DONE
 
-  AZ=R:B=1:GOSUB PR_STR: REM MAL_PRINT
+  AZ=R:B=1:GOSUB PR_STR: REM inlined PRINT
 
   REP_DONE:
-    REM Release memory from MAL_READ and EVAL
+    REM Release memory from EVAL
     AY=R2:GOSUB RELEASE
-    AY=R1:GOSUB RELEASE
 END SUB
 
 REM MAIN program
@@ -244,7 +244,7 @@ MAIN:
     IF EZ=1 THEN GOTO QUIT
     IF R$="" THEN GOTO REPL_LOOP
 
-    A$=R$:CALL REP: REM call REP
+    A$=R$:CALL REP
 
     IF ER<>-2 THEN GOSUB PRINT_ERROR:GOTO REPL_LOOP
     PRINT R$
@@ -263,4 +263,3 @@ MAIN:
     PRINT "Error: "+E$
     ER=-2:E$=""
     RETURN
-

impls/basic/step3_env.in.bas

@@ -47,7 +47,6 @@ SUB EVAL_AST
       REM release it below)
       IF T=8 THEN N=M:M=Z%(A+2):Z%(M)=Z%(M)+32
 
-
       REM update the return sequence structure
       REM release N (and M if T=8) since seq takes full ownership
       C=1:GOSUB MAP_LOOP_UPDATE
@@ -183,8 +182,6 @@ SUB EVAL
       F=Z%(R+2)
 
       GOSUB TYPE_F
-
-      REM ON .. GOTO here reduces the diff with later steps.
       T=T-8
       IF 0<T THEN ON T GOTO EVAL_DO_FUNCTION
 
@@ -204,10 +201,6 @@ SUB EVAL
     REM AZ=R: B=1: GOSUB PR_STR
     REM PRINT "EVAL_RETURN R: ["+R$+"] ("+STR$(R)+"), LV:"+STR$(LV)+",ER:"+STR$(ER)
 
-    REM release environment if not the top one on the stack
-    GOSUB PEEK_Q_1
-    IF E<>Q THEN AY=E:GOSUB RELEASE
-
     LV=LV-1: REM track basic return stack level
 
     REM release everything we couldn't release earlier
@@ -257,24 +250,36 @@ DO_FUNCTION:
 
 REM PRINT is inlined in REP
 
-REM REP(A$) -> R$
+REM RE(A$) -> R
 REM Assume D has repl_env
-SUB REP
+REM caller must release result
+RE:
   R1=-1
-  GOSUB READ_STR: REM inlined MAL_READ
+  GOSUB READ_STR: REM inlined READ
   R1=R
-  IF ER<>-2 THEN GOTO REP_DONE
+  IF ER<>-2 THEN GOTO RE_DONE
 
   A=R:E=D:CALL EVAL
+
+  RE_DONE:
+    REM Release memory from READ
+    AY=R1:GOSUB RELEASE
+    RETURN: REM caller must release result of EVAL
+
+REM REP(A$) -> R$
+REM Assume D has repl_env
+SUB REP
+  R2=-1
+
+  GOSUB RE
   R2=R
   IF ER<>-2 THEN GOTO REP_DONE
 
-  AZ=R:B=1:GOSUB PR_STR: REM MAL_PRINT
+  AZ=R:B=1:GOSUB PR_STR: REM inlined PRINT
 
   REP_DONE:
-    REM Release memory from MAL_READ and EVAL
+    REM Release memory from EVAL
     AY=R2:GOSUB RELEASE
-    AY=R1:GOSUB RELEASE
 END SUB
 
 REM MAIN program
@@ -285,8 +290,8 @@ MAIN:
 
   REM create repl_env
   C=0:GOSUB ENV_NEW:D=R
-
   E=D
+
   REM + function
   T=9:L=1:GOSUB ALLOC: REM native function
   B$="+":C=R:GOSUB ENV_SET_S
@@ -310,7 +315,7 @@ MAIN:
     IF EZ=1 THEN GOTO QUIT
     IF R$="" THEN GOTO REPL_LOOP
 
-    A$=R$:CALL REP: REM call REP
+    A$=R$:CALL REP
 
     IF ER<>-2 THEN GOSUB PRINT_ERROR:GOTO REPL_LOOP
     PRINT R$
@@ -329,4 +334,3 @@ MAIN:
     PRINT "Error: "+E$
     ER=-2:E$=""
     RETURN
-