[BASIC] Fix 1E39 bug (Issue #247)

basic/code17.s

@@ -4,36 +4,57 @@ conint	jsr posint
 	bne gofuc
 	ldx faclo
 	jmp chrgot
-val	jsr len1
-val_str	bne @1
+
+; the "val" function takes a string and turns it into a number by interpreting
+; the ascii digits etc. Except for the problem that a terminator must be
+; supplied by replacing the character beyond the string, VAL is merely a call
+; to floating point input ("finh").
+val	jsr len1        ;get length
+val_str	bne @1      ;return 0 if len=0
 	jmp zerofc
-@1:	ldx txtptr
+@1:	ldx txtptr      ;save current txtptr
 	ldy txtptr+1
-	stx strng2
-	sty strng2+1
-	ldx index1
-	stx txtptr
-	clc
-	adc index1
-	sta index2
-	ldx index1+1
-	stx txtptr+1
-	bcc val2
-	inx
-val2	stx index2+1
-	lda (index2)
+	phy
+	phx
+	ldx index1      ;save current index1
+	ldy index1+1
+	phy
+	phx
 	pha
-	lda #0
-	sta (index2)
+	inc
+	beq val_strlong
+	jsr strspa     ;allocate memory for string (this destroys index1, but we saved it to stack)
+	plx            ;restore saved string length
+	pla
+	sta index1     ;restore saved index1
+	pla
+	sta index1+1
+	lda dsctmp+1   ;fetch string space pointer
+	sta txtptr     ;update txtptr with dsctmp
+	lda dsctmp+2
+	sta txtptr+1
+	ldy #0         ;initalize Y to begin copying the string
+@2:	lda (index1),y ;load current byte
+	sta (txtptr),y ;store it in allocated memory
+	iny
+	dex
+	bne @2         ;loop until string is copied
+	lda #0         ;load null terminator byte
+	sta (txtptr),y ;write it to the end of the string
 	jsr chrgot
 	jsr finh
-	pla
-	sta (index2)
-st2txt	ldx strng2
+	plx            ;restore saved txtptr
+	ply
+	stx txtptr
+	sty txtptr+1
+	rts            ;done!
+st2txt	ldx strng2 ;restore text pointer
 	ldy strng2+1
 	stx txtptr
 	sty txtptr+1
-valrts	rts
+valrts	rts        ;done!
+val_strlong	ldx #errls
+	jmp error
 getnum	jsr frmadr
 combyt	jsr chkcom
 	jmp getbyt