From cb3e6469b825d64dbb5f82363ef12565808b305c Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Thu, 26 Mar 2020 14:47:17 -0400
Subject: [PATCH] forth: make "(parsed)" support negative literals

This limitation was becoming annoying...
---
 forth/forth.asm | 15 +++++++++++++++
 forth/z80c.fs   |  4 ++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/forth/forth.asm b/forth/forth.asm
index 742804f..ae2381a 100644
--- a/forth/forth.asm
+++ b/forth/forth.asm
@@ -296,6 +296,8 @@ strskip:
 parseDecimal:
 	; First char is special: it has to succeed.
 	ld	a, (hl)
+	cp	'-'
+	jr	z, .negative
 	; Parse the decimal char at A and extract it's 0-9 numerical value. Put the
 	; result in A.
 	; On success, the carry flag is reset. On error, it is set.
@@ -349,6 +351,19 @@ parseDecimal:
 	cp	a	; ensure Z
 	ret
 
+.negative:
+	inc	hl
+	call	parseDecimal
+	ret	nz
+	push	hl	; --> lvl 1
+	or	a	; clear carry
+	ld	hl, 0
+	sbc	hl, de
+	ex	de, hl
+	pop	hl	; <-- lvl 1
+	xor	a	; set Z
+	ret
+
 ; *** Support routines ***
 ; Find the entry corresponding to word where (HL) points to and sets DE to
 ; point to that entry.
diff --git a/forth/z80c.fs b/forth/z80c.fs
index fbe7ac5..183d848 100644
--- a/forth/z80c.fs
+++ b/forth/z80c.fs
@@ -130,7 +130,7 @@ CODE *
     DE INCss,
 ( noinc )
     A DECr,
-    0 12 - JRNZe, ( loop )
+    -12 JRNZe, ( loop )
     HL PUSHqq,
 ;CODE
 
@@ -154,7 +154,7 @@ CODE /MOD
     DE ADDHLss,
     C DECr,
 ( skip )
-    0 12 - DJNZe, ( loop )
+    -12 DJNZe, ( loop )
     B A LDrr,
     HL PUSHqq,
     BC PUSHqq,