zasm: improve comma processing

We don't treat "," exactly as a whitespace anymore. We have specific
processing for it.

apps/zasm/instr.asm

@@ -710,15 +710,9 @@ getUpcode:
 	pop	ix
 	ret
 
-; Parse next argument in I/O and place it in (DE)
+; Parse argument in (HL) and place it in (DE)
 ; Sets Z on success, reset on error.
 processArg:
-	call	readWord
-	jr	nz, .noarg
-	; Read word is in (HL). Now, let's push
-	; that HL value and replace it with (scratchpad) so that we can parse
-	; that arg.
-
 	call	parseArg
 	cp	0xff
 	jr	z, .error
@@ -737,10 +731,6 @@ processArg:
 .error:
 	call	unsetZ
 	ret
-.noarg:
-	xor	a
-	ld	(de), a
-	ret
 
 ; Parse instruction specified in A (I_* const) with args in I/O and write
 ; resulting opcode(s) in (instrUpcode). Returns the number of bytes written in
@@ -752,12 +742,22 @@ parseInstruction:
 	; A is reused in matchPrimaryRow but that register is way too changing.
 	; Let's keep a copy in a more cosy register.
 	ld	c, a
+	xor	a
+	ld	(curArg1), a
+	ld	(curArg2), a
+	call	readWord
+	jr	nz, .nomorearg
 	ld	de, curArg1
 	call	processArg
 	jr	nz, .error
+	call	readComma
+	jr	nz, .nomorearg
+	call	readWord
+	jr	nz, .error
 	ld	de, curArg2
 	call	processArg
 	jr	nz, .error
+.nomorearg:
 	; Parsing done, no error, let's move forward to instr row matching!
 	ld	de, instrTBl
 	ld	b, INSTR_TBL_CNT

apps/zasm/tok.asm

@@ -34,8 +34,6 @@ isSep:
 	cp	' '
 	ret	z
 	cp	0x09
-	ret	z
-	cp	','
 	ret
 
 ; Sets Z is A is ' ', ',', ';', CR, LF, or null.
@@ -100,6 +98,8 @@ readWord:
 	call	ioGetC
 	call	isSepOrLineEnd
 	jr	z, .success
+	cp	','
+	jr	z, .success
 	djnz	.loop2
 	; out of space. error.
 .error:
@@ -118,6 +118,16 @@ readWord:
 	pop	bc
 	ret
 
+; Reads the next char in I/O. If it's a comma, Set Z and return. If it's not,
+; Put the read char back in I/O and unset Z.
+readComma:
+	call	ioGetC
+	cp	','
+	ret	z
+	call	ioPutBack
+	call	unsetZ
+	ret
+
 ; Read ioGetC until we reach the beginning of next line, skipping comments if
 ; necessary. This skips all whitespace, \n, \r, comments until we reach the
 ; first non-comment character. Then, we put it back (ioPutBack) and return.