From 3ff72ed7c229ec2edf663f89eb2b7a9e47af36b9 Mon Sep 17 00:00:00 2001
From: Leo C
Date: Thu, 4 Apr 2019 23:04:02 +0200
Subject: Some cosmetic changes and minor optimizations

---
 ddt180.z80 | 116 ++++++++++++++++++++++++++++---------------------------------
 1 file changed, 54 insertions(+), 62 deletions(-)

diff --git a/ddt180.z80 b/ddt180.z80
index 220c074..60c588a 100644
--- a/ddt180.z80
+++ b/ddt180.z80
@@ -146,9 +146,7 @@ conbuf:
 	ld sp,stack
 	exx
 	ld de,ddtz_base
-	or a
-	sbc hl,de
-	add hl,de
+	call cp_hl_de
 	jr c,l0079h
 	ex de,hl
 l0079h:
@@ -214,6 +212,11 @@ CMDTAB:
 	dw	cmd_Y		;examine [and substitute] Y variables
 	dw	cmd_Z		;Zap (fill) memory with a byte string
 
+ERROR:
+	ld hl,(error_func)
+exe_hl:
+	call CALL_HL
+	;fall thru
 mainloop:
 	ld sp,stack
 	ld hl,p_msg_error
@@ -223,6 +226,7 @@ mainloop:
 	call bp_clr_temporary
 	ld hl,(cmd_rpt)
 	ld de,mainloop
+	ld (cmd_rpt),de
 	call cp_hl_de
 	ld a,'>'
 	call outchar
@@ -231,8 +235,6 @@ mainloop:
 	call get_line
 	call skipbl
 	jr z,exe_hl
-	ld hl,mainloop
-	ld (cmd_rpt),hl
 	inc de
 	sub '@'
 	jr c,ERROR
@@ -247,12 +249,6 @@ mainloop:
 	ld l,a
 	jr exe_hl
 
-ERROR:
-	ld hl,(error_func)
-exe_hl:
-	call CALL_HL
-	jr mainloop
-
 ;-------------------------------------------------------------------------------
 
 p_msg_error:
@@ -261,7 +257,7 @@ p_msg_error:
 	;fall thru
 crlf:
 	call	pstr_inl
-	db	CR,LF+80h
+	dc	CR,LF
 	call inchar
 	ld a,0
 	ld (con_col),a
@@ -431,7 +427,6 @@ pstr:
 	and a
 	ret z
 	call outchar
-	and a
 	ret m
 	jr pstr
 
@@ -470,11 +465,11 @@ inchar:
 	ld c,BDOS_CSTAT
 	call ddtz_bdos
 	and a
-	jr z,l0284h
+	jr z,inch1
 	ld c,BDOS_CIN
 	call ddtz_bdos
 	scf
-l0284h:
+inch1:
 	pop bc
 	pop de
 	pop hl
@@ -531,12 +526,13 @@ skipbl:
 	or a
 	ret
 
+;-------------------------------------------------------------------------------
+
 next_arg:
 	call skipbl
 	cp ','
 	ret nz
-	inc de
-	call skipbl
+	call skipbl0
 	cp a
 	ret
 
@@ -580,8 +576,8 @@ sub_hl_a1:
 sub_hl_a:
 	push	bc
 	ld	c,a
-	ld	b,0
-	or	a
+	xor	a
+	ld	b,a
 	sbc	hl,bc
 	pop	bc
 	ret
@@ -693,7 +689,7 @@ l030ch:
 sub_0318h:
 	push bc
 	res 7,b
-	defb 03eh		;ld a,nn
+	defb 03eh		;ld a,nn: swallow push bc
 sub_031ch:
 	push bc
 	push de
@@ -1096,6 +1092,7 @@ do_factor:
 	ret nc
 	inc de
 	ld hl,(BDOS+1)
+	dec hl
 	cp 'T'
 	ret z
 	ld hl,(high_load)
@@ -2137,11 +2134,11 @@ cmd_X:
 	jp nc,p_cpustat0
 	call assert_eol
 	ld a,b
-	cp 01eh
+	cp 30
 	jr z,l0c5fh
-	cp 01fh
+	cp 31
 	jr z,l0c4fh
-	cp 01dh
+	cp 29
 	jp z,ERROR
 	ex de,hl
 	ld hl,t_reg_names
@@ -2258,38 +2255,38 @@ sub_0caeh:
 	ret
 
 t_reg_names:
-	DC	'BC'''
-	DC	'DE'''
-	DC	'HL'''
-	DC	'BC'
-	DC	'DE'
-	DC	'HL'
-	DC	'A'''
-	DC	'B'''
-	DC	'C'''
-	DC	'D'''
-	DC	'E'''
-	DC	'H'''
-	DC	'L'''
-	DC	'A'
-	DC	'B'
-	DC	'C'
-	DC	'D'
-	DC	'E'
-	DC	'H'
-	DC	'L'
-	DC	'IX'
-	DC	'IY'
-	DC	'SP'
-	DC	'PC'
-	DC	'X'
-	DC	'Y'
-	DC	'S'
-	DC	'P'
-	DC	'I'
-	DC	'IP'
-	DC	'F'''
-	DC	'F'
+	DC	'BC'''		;0
+	DC	'DE'''		;1
+	DC	'HL'''		;2
+	DC	'BC'		;3
+	DC	'DE'		;4
+	DC	'HL'		;5
+	DC	'A'''		;6
+	DC	'B'''		;7
+	DC	'C'''		;8
+	DC	'D'''		;9
+	DC	'E'''		;10
+	DC	'H'''		;11
+	DC	'L'''		;12
+	DC	'A'		;13
+	DC	'B'		;14
+	DC	'C'		;15
+	DC	'D'		;16
+	DC	'E'		;17
+	DC	'H'		;18
+	DC	'L'		;19
+	DC	'IX'		;20
+	DC	'IY'		;21
+	DC	'SP'		;22
+	DC	'PC'		;23
+	DC	'X'		;24
+	DC	'Y'		;25
+	DC	'S'		;26
+	DC	'P'		;27
+	DC	'I'		;28
+	DC	'IP'		;29
+	DC	'F'''		;30
+	DC	'F'		;31
 	DB	0
 
 b_0cfa_start:
@@ -2417,7 +2414,6 @@ msg_@:
 ;      Input a byte from port
 
 cmd_I:
-	ld hl,cmd_I
 	ld (cmd_rpt),hl
 	ld hl,(last_I)
 	call get_lastarg_def
@@ -2437,7 +2433,6 @@ cmd_I:
 ;      Output a byte to a port
 
 cmd_O:
-	ld hl,cmd_O
 	ld (cmd_rpt),hl
 	ld hl,(last_O_val)
 	call get_arg_def
@@ -2646,7 +2641,7 @@ l0e96h:
 	add hl,bc
 l0ea7h:
 	ld bc,16
-	and a
+	and a			;clear carry
 	call sub_0f58h
 	pop hl
 	pop bc
@@ -2783,7 +2778,6 @@ l0f42h:
 ;      Display memory in hex and ASCII
 
 cmd_D:
-	ld hl,cmd_D
 	ld (cmd_rpt),hl
 	ld hl,(last_D)
 	ld bc,128
@@ -3379,6 +3373,7 @@ p_max_high:
 	call pstr_inl
 	DC	'  Top = '
 	ld hl,(BDOS+1)
+	dec hl
 	call out_hl
 	jp crlf
 
@@ -4619,7 +4614,6 @@ test_paren_close:
 ;      List disassembled code
 
 cmd_L:
-	ld hl,cmd_L
 	ld (cmd_rpt),hl
 	call expr
 	jr nc,l18dbh
@@ -5890,7 +5884,6 @@ l2113h:
 ;     trace over Calls [No list] [Jumps only] /.While./.Until.
 
 cmd_C:
-	ld hl,cmd_C
 	ld a,1
 	jr cmd_tc
 
@@ -5902,7 +5895,6 @@ cmd_C:
 
 cmd_T:
 	xor a
-	ld hl,cmd_T
 cmd_tc:
 	ld (cmd_rpt),hl
 	ld (trace_call_flag),a
-- 
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