more work towards arrays support

src/basic/engine_runtime/check_stack_space.s

@@ -5,8 +5,12 @@
 
 check_stack_space:
 
+	phx_trash_a
+
 	tsx
 	cpx #$60                           // XXX is this a safe threshold?
 	bcc_16 do_FORMULA_TOO_COMPLEX_error
 
+	plx_trash_a
+
 	rts

src/basic/engine_variables/array_create.s

@@ -49,9 +49,7 @@ array_create_fetch_dims_loop:
 
 	// Check if the stack has reasonable space free
 
-	phx_trash_a
 	jsr check_stack_space
-	plx_trash_a
 
 	// Fetch the dimension, increment it by 1, and put it on the stack;
 	// confirmed with original ROM, that it also stores dimensions in the reverse order

src/basic/engine_variables/fetch_variable.s

@@ -69,13 +69,9 @@ fetch_variable_adjust_VARPNT:
 
 #if !HAS_OPCODES_65CE02
 
-	clc
-	lda VARPNT+0
-	adc #$02
-	sta VARPNT+0
-	bcc !+
-	inc VARPNT+1
-!:
+	lda #$02
+	jsr helper_VARPNT_up_A
+
 #else // HAS_OPCODES_65CE02
 
 	inw VARPNT
@@ -91,13 +87,10 @@ fetch_variable_find_addr_next:
 	// Increase VARPNT by 7 - constant value, each variable uses 7 bytes, see:
 	// - https://sites.google.com/site/h2obsession/CBM/basic/variable-format
 
-	clc
-	lda VARPNT+0
-	adc #$07
-	sta VARPNT+0
-	bcc fetch_variable_find_addr_loop
-	inc VARPNT+1
-	bne fetch_variable_find_addr_loop  // branch always
+	lda #$07
+	jsr helper_VARPNT_up_A
+
+	jmp_8 fetch_variable_find_addr_loop
 
 fetch_variable_alocate:
 	

src/basic/engine_variables/fetch_variable_arr.s

@@ -10,13 +10,110 @@ fetch_variable_arr:
 
 	// Array does not exist - we will have to create one with default parameters
 
-	lda #$00
-	sta VARPNT+1
+	// XXX implement this
+
+	jmp do_NOT_IMPLEMENTED_error
 !:
 	// Fetch the 'coordinates'
 
+	ldx #$00                                     // counts number of dimensions
+
+	// FALLTROUGH
+
+fetch_variable_arr_fetch_coords_loop:
+
+	inx
+
+	// Check if the stack has reasonable space free
+
+	jsr check_stack_space
+
+	// Fetch the dimension and put it on the stack
+
+	jsr fetch_uint16
+	bcs_16 do_SYNTAX_error
+
+	lda LINNUM+0
+	pha
+	lda LINNUM+1
+	pha
+
+	// Check if more dimensions are given
+
+	jsr fetch_character_skip_spaces
+	cmp #$2C                                     // ','
+	beq fetch_variable_arr_fetch_coords_loop
+	cmp #$29                                     // ')'
+	bne_16 do_SYNTAX_error
+
+	// FALLTROUGH
+
+fetch_variable_arr_check_dimensions:
+
+	// Check if the number of dimensions matches the stored ones
+
+#if CONFIG_MEMORY_MODEL_60K
+	
+	// XXX
+	// XXX
+	// XXX
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+
+	// XXX
+	// XXX
+	// XXX
+
+#else // CONFIG_MEMORY_MODEL_38
+
+	ldy #$04
+	txa
+	cmp (VARPNT), y
+
+#endif
+
+	bne_16 do_BAD_SUBSCRIPT_error
+
+	// FALLTROUGH
+
+fetch_variable_arr_calc_pos:
+
+	// Move VARPNT po point to sizes in each dimension
+
+	lda #$05
+	jsr helper_VARPNT_up_A
+
+	// Set previous dimension size as '1'
+
 	// XXX implement this
 
-	// XXX finish the implementation
+	// FALLTROUGH
+
+fetch_variable_arr_calc_pos_loop:
+
+	// Fetch the coordinate from stack
+
+	// XXX implement this
+
+	// Compare current coordinate with current dimension size
+
+	// XXX implement this
+
+	// Multiply current coordinate with previous dimension
+
+	// XXX implement this
+
+	// Store current dimension, for the next iteration
+
+	// XXX implement this
+
+	// Check if there are more dimensions to handle
+
+	dex
+	bne fetch_variable_arr_calc_pos_loop
+
+	// Increment VARPNT by the calculated offset and quit
+
+	// XXX implement this
 
 	jmp do_NOT_IMPLEMENTED_error

src/basic/engine_variables/helper_varpnt_up_A.s

@@ -0,0 +1,18 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Helper routine, used by various variable-related routines
+//
+
+
+helper_VARPNT_up_A:                  // .A - bytes to increment VARPNT
+
+	clc
+	adc VARPNT+0
+	sta VARPNT+0
+	bcc !+
+	inc VARPNT+1
+!:
+	rts