string handling fixes

src/basic/basic_commands/cmd_let.s

@@ -9,6 +9,7 @@ cmd_let:
 	// Fetch variable name, should be followed by assign operator
 
 	jsr fetch_variable
+	bcs_16 do_SYNTAX_error
 	jsr injest_assign
 	bcs_16 do_SYNTAX_error
 
@@ -148,15 +149,35 @@ cmd_let_assign_string:
 
 	// First special case - check if the new string has size 0
 
+	lda DSCPNT+0
+	bne cmd_let_assign_string_not_empty
+
+	// XXX free old string data
+
+	// Set the new variable as size 0
+
+#if CONFIG_MEMORY_MODEL_60K
+	
 	// XXX
+	// XXX: implement this
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+
+
+#endif
+
+	rts
+
+cmd_let_assign_string_not_empty:
 
 	// Check if the source and destination strings are the same (VARPNT should now point just after variable name)
 
-	lda VARPNT+1
+	lda VARPNT+0
 	cmp __FAC1+1
 	bne !+
 	iny
-	lda VARPNT+2
+	lda VARPNT+1
 	cmp __FAC1+2
 	bne !+
 

src/basic/engine/ad9e.frmevl.s

@@ -68,9 +68,19 @@ FRMEVL_loop:
 	// $7F has to be a function
 
 	cmp #$80                           // check for a token
-	bcc FRMEVL_execute_function
+	bcs FRMEVL_execute_function
 
-	// There are 2 possibilities left - a floating point value or a variable
+	// Check for a variable
+
+#if !HAS_OPCODES_65CE02
+	jsr unconsume_character
+#else
+	dew TXTPTR
+#endif
+	jsr fetch_variable
+	bcc FRMEVL_got_value
+
+	// There is one possibility left - a floating point value
 
 
 	// XXX implement this part
@@ -279,7 +289,7 @@ FRMEVL_push_operator_address:
 	// as this is the place where unary operator support calls
 
 	tsx
-	cpx #$40                           // XXX is this a safe threshold?
+	cpx #$60                           // XXX is this a safe threshold?
 	bcc_16 do_FORMULA_TOO_COMPLEX_error
 
 	// Push the operator address to stack, in a form

src/basic/engine/fetch_variable.s

@@ -2,6 +2,10 @@
 // #LAYOUT# *   BASIC_0 #TAKE
 // #LAYOUT# *   *       #IGNORE
 
+//
+// Carry set = failure, not recognized variable name
+//
+
 
 fetch_variable:
 
@@ -14,8 +18,17 @@ fetch_variable:
 
 	jsr fetch_character_skip_spaces
 	jsr is_AZ
-	bcs_16 do_SYNTAX_error
+	bcc !+
 
+#if !HAS_OPCODES_65CE02
+	jsr unconsume_character
+#else
+	dew TXTPTR
+#endif
+
+	sec
+	rts
+!:
 	sta VARNAM+0
 
 	// Fetch the (optional) second character
@@ -96,7 +109,7 @@ fetch_variable_find_addr_loop:
 	cmp ARYTAB+1
 	bne !+
 	lda VARPNT+0
-	cmp VARPNT+0
+	cmp ARYTAB+0
 	beq fetch_variable_alocate
 !:
 	// Compare current variable name with searched one
@@ -151,6 +164,7 @@ fetch_variable_adjust_VARPNT:
 
 #endif
 
+	clc
 	rts
 
 fetch_variable_find_addr_next:
@@ -168,82 +182,87 @@ fetch_variable_find_addr_next:
 
 fetch_variable_alocate:
 	
-	// First check if we have enough space for a new descriptor
+	// First check if we have enough space for a new descriptor (if FRETOP - STREND >= 7)
 
-#if CONFIG_MEMORY_MODEL_60K
+	sec
-	
+	lda FRETOP+0
-	// XXX
+	sbc STREND+0
-	// XXX: implement this
+	pha
-	// XXX
+	lda FRETOP+1
+	sbc STREND+1
+	bne !+                             // branch if high byte of result > 0
 
-#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	pla
-	// XXX consider optimized version without multiple JSRs
+	cmp #$07
+	bcs fetch_variable_alocate_space_OK
 
-	// XXX
+	jmp do_OUT_OF_MEMORY_error
-	// XXX: implement this
+!:
-	// XXX
+	pla
 
-#else // CONFIG_MEMORY_MODEL_38K
+	// FALLTROUGH
 
-	// XXX
+fetch_variable_alocate_space_OK:
-	// XXX: implement this
-	// XXX
-
-#endif
 
 	// If needed, move all the arrays up
 
 #if CONFIG_MEMORY_MODEL_60K
 	
 	// XXX
-	// XXX: implement this
+	// XXX: implement this for arrays
 	// XXX
 
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 	// XXX consider optimized version without multiple JSRs
 
 	// XXX
-	// XXX: implement this
+	// XXX: implement this for arrays
 	// XXX
 
 #else // CONFIG_MEMORY_MODEL_38K
 
 	// XXX
-	// XXX: implement this
+	// XXX: implement this for arrays
 	// XXX
 
 #endif
 
-	// Set pointer to new variable
+	// Adjust ARYTAB and STREND
 
-#if CONFIG_MEMORY_MODEL_60K
+	clc
-	
+	lda STREND+0
-	// XXX
+	adc #$07
-	// XXX: implement this
+	sta STREND+0
-	// XXX
+	bcc !+
+	inc STREND+1
+!:
 
-#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	clc
-	// XXX consider optimized version without multiple JSRs
+	lda ARYTAB+0
-
+	adc #$07
-	// XXX
+	sta ARYTAB+0
-	// XXX: implement this
+	bcc !+
-	// XXX
+	inc ARYTAB+1
-
+!:
-#else // CONFIG_MEMORY_MODEL_38K
+	// VARPNT already points to the start of the variable descriptor
-
-	// XXX
-	// XXX: implement this
-	// XXX
-
-#endif
 
 	// Fill-in the new variable name, descriptor (it is enough to zero first 2 bytes of content)
 
 	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
-	
+
-	// XXX
+	ldx #<VARNAM
+	lda VARNAM+0
+	jsr poke_under_roms
+	iny
+	lda VARNAM+1
+	jsr poke_under_roms
+	iny
+	lda #$00
+	jsr poke_under_roms
+	iny
+	jsr poke_under_roms
 
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 	

src/basic/engine/varstr_alloc.s

@@ -19,7 +19,7 @@
 //
 
 // XXX test this routine
-// XXX make it compatible with under-ROM routines
+// XXX change DSCPNT to use standard descriptor format
 
 varstr_alloc:
 

src/basic/engine/varstr_alloc_fretop.s

@@ -6,6 +6,8 @@
 // Helper routines for 'varstr_alloc'
 //
 
+// XXX change DSCPNT to use standard descriptor format
+
 varstr_FRETOP_down_A:                  // .A - bytes to lower FRETOP, uses DSCPNT+2
 
 	sta DSCPNT+2 

src/basic/engine/varstr_free.s

@@ -12,7 +12,8 @@
 // XXX test this routine
 
 // XXX handle strings located in program area
-// XXX change DSCPNT format to be compliant with all other descriptors
+
+// XXX change DSCPNT to use standard descriptor format
 
 varstr_free:
 

src/basic/engine/varstr_free_fretop.s

@@ -6,6 +6,8 @@
 // Helper routines for 'varstr_free'
 //
 
+// XXX change DSCPNT to use standard descriptor format
+
 varstr_FRETOP_up:                    // DSCPNT+2 - bytes to increment FRETO, uses DSCPNT+2
 
 	clc

src/basic/engine/varstr_garbage_collect.s

@@ -4,8 +4,7 @@
 
 // XXX test this routine
 
-// XXX change DSCPNT format to be compliant with all other descriptors
+// XXX change DSCPNT to use standard descriptor format
-
 
 varstr_garbage_collect: