some more work on string assignment

CREDITS.md

@@ -24,6 +24,11 @@
 * silverdr - for the floating point routines [description](https://codebase64.org/doku.php?id=base:kernal_floating_point_mathematics)
 * the [C64 Wiki](https://www.c64-wiki.com) contributors
 
+## other
+
+* Gábor Lénárt - for his work on [XEMU Mega65 emulator](https://github.com/lgblgblgb/xemu)
+* Mads Nielsen - for the [Kick Assembler](http://www.theweb.dk/KickAssembler/Main.html#frontpage)
+
 <br />
 
 * ... and all the others we forgot

src/basic/basic_commands/cmd_let.s

@@ -117,6 +117,77 @@ cmd_let_assign_string:
 	lda VALTYP
 	bpl_16 do_TYPE_MISMATCH_error
 
+	// Copy the string descriptor to DSCPNT
+
+#if CONFIG_MEMORY_MODEL_60K
+	
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	// XXX consider optimized version without multiple JSRs
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38K
+
+	ldy #$00
+	lda (VARPNT), y
+	sta DSCPNT+0
+	iny
+	lda (VARPNT), y
+	sta DSCPNT+1
+	iny
+	lda (VARPNT), y
+	sta DSCPNT+2
+
+#endif
+
+	// First special case - check if the new string has size 0
+
+	// XXX
+
+	// Check if the source and destination strings are the same (VARPNT should now point just after variable name)
+
+	lda VARPNT+1
+	cmp __FAC1+1
+	bne !+
+	iny
+	lda VARPNT+2
+	cmp __FAC1+2
+	bne !+
+
+	// If we are here, than both source and destination strings are the same - nothing more to be done
+
+	rts
+!:
+	// Strings are not the same - check if the new one is located within a text area, between TXTTAB and VARTAB
+
+	// XXX
+
+	// Check if size of both equals and the old on is above FRETOP
+
+	// XXX
+
+	// Check if new one is at least 3 bytes shorter and the old one is above FRETOP
+
+	// XXX
+
+	// Free the memory of the old string, it is not possible to reuse it
+
+	// XXX
+
+	// Check if the new string is a temporary one - if so, reuse already done alocation
+
+	// XXX
+
+	// No special case optimization is possible - alocate new memory area and copy the string
+
+	// XXX
+
 #if CONFIG_MEMORY_MODEL_60K
 	
 	// XXX

src/basic/engine/fetch_variable.s

@@ -133,7 +133,7 @@ fetch_variable_find_addr_loop:
 
 fetch_variable_adjust_VARPNT:
 
-	// Adjust VARPNT to point just after variable name and quit
+	// Adjust VARPNT to point just after variable name (XXX is it needed?) and quit
 
 #if !HAS_OPCODES_65CE02
 
@@ -170,15 +170,72 @@ fetch_variable_alocate:
 	
 	// First check if we have enough space for a new descriptor
 
+#if CONFIG_MEMORY_MODEL_60K
+	
 	// XXX
+	// XXX: implement this
+	// XXX
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	// XXX consider optimized version without multiple JSRs
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38K
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#endif
 
 	// If needed, move all the arrays up
 
+#if CONFIG_MEMORY_MODEL_60K
+	
 	// XXX
+	// XXX: implement this
+	// XXX
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	// XXX consider optimized version without multiple JSRs
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38K
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#endif
 
 	// Set pointer to new variable
 
+#if CONFIG_MEMORY_MODEL_60K
+	
 	// XXX
+	// XXX: implement this
+	// XXX
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	// XXX consider optimized version without multiple JSRs
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38K
+
+	// XXX
+	// XXX: implement this
+	// XXX
+
+#endif
 
 	// Fill-in the new variable name, descriptor (it is enough to zero first 2 bytes of content)
 

src/basic/engine/varstr_free.s

@@ -11,6 +11,9 @@
 
 // XXX test this routine
 
+// XXX handle strings located in program area
+// XXX change DSCPNT format to be compliant with all other descriptors
+
 varstr_free:
 
 	// First copy the string descriptor data to DSCPNT

src/basic/engine/varstr_garbage_collect.s

@@ -4,6 +4,9 @@
 
 // XXX test this routine
 
+// XXX change DSCPNT format to be compliant with all other descriptors
+
+
 varstr_garbage_collect:
 
 	// The routine utilizes the 'shift_mem_up' - which leaves INDEX+0 and INDEX+1