From 7c34d57d2c15a5d63546f3d62c7e946e05f01856 Mon Sep 17 00:00:00 2001
From: "B. Watson" <urchlay@slackware.uk>
Date: Wed, 10 Jul 2024 15:09:10 -0400
Subject: whichbas: simplify and complete logic for op tokens 0x66-0x68, aka %0
 %1 %2 or LEFT$( RIGHT$( MID$(.

---
 whichbas.c | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/whichbas.c b/whichbas.c
index 54a4f03..2b84285 100644
--- a/whichbas.c
+++ b/whichbas.c
@@ -284,6 +284,21 @@ int is_string_op(unsigned char tok) {
 		is_string_exp_op (tok) ;
 }
 
+/* true if an operator token is a string function in BASIC XL (or XE).
+   these tokens are all numeric functions in Turbo, so be sure you
+   know what you're doing! */
+int is_bxl_string_func(unsigned char tok) {
+	switch(tok) {
+		case 0x5c: /* BXL HEX$, Turbo DEC */
+		case 0x66: /* BXL LEFT$, Turbo %0 */
+		case 0x67: /* BXL RIGHT$, Turbo %1 */
+		case 0x68: /* BXL MID$, Turbo %2 */
+			return 1;
+		default:
+			return 0;
+	}
+}
+
 void remove_type(int type) {
 	bas_type &= ((~type) & 0x0f);
 
@@ -800,20 +815,14 @@ CALLBACK(handle_op) {
 		case 0x66: /* %0 in TB, LEFT$( (pseudo-func, takes string) in BXL/BXE */
 		case 0x67: /* %1 in TB, RIGHT$( (pseudo-func, takes string) in BXL/BXE */
 		case 0x68: /* %2 in TB, MID$( (pseudo-func, takes string) in BXL/BXE */
-			/* PARTIAL: doesn't handle LEFT$/etc first arg being a string func. */
-			if(nexttok == OP_STRCONST || nexttok >= 0x80) {
-				/* %0 %1 %2 can't be followed by a string constant *or* a variable */
+			/* COMPLETE */
+			/* LEFT$/RIGHT$/MID$ do NOT get OP_FUNC_LPAR (the "(" is part of the
+			   token name). They're always followed by a string operator... and
+			   it works out that none of the tokens for BXL-only string funcs
+			   are allowed to follow %0 %1 %2 in Turbo. */
+			if(is_string_op(nexttok) || is_bxl_string_func(nexttok)) {
 				remove_type(BT_TURBO);
-			/* Can't do, due to LEFT$(HEX$("1234"), 1) (or STR$, etc): */
-			/* } else {
-				remove_type(BT_BXL_BXE); */
-			/* ...but this stuff helps: */
-			} else if(nexttok == OP_EOS || nexttok == OP_EOL) {
-				/* LEFT$ RIGHT$( MID$( can't occur at the end of a statement. */
-				remove_type(BT_BXL_BXE);
-			} else if(pos == (last_cmd_pos + 2) && program[pos - 1] == OP_NUM_ASSIGN) {
-				/* LEFT$ RIGHT$( MID$( return strings, assignment would
-				   be OP_STR_ASSIGN. */
+			} else {
 				remove_type(BT_BXL_BXE);
 			}
 			break;
-- 
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