more work towards arrays

src/basic/engine_variables/assign_variable.s

@@ -37,6 +37,8 @@ assign_variable:
 	jsr is_var_ST
 	beq_16 do_SYNTAX_error
 
+	// XXX add support for arrays
+
 	// Retrieve the variable address
 
 	jsr fetch_variable_find_addr

src/basic/engine_variables/fetch_variable_arr.s

@@ -16,6 +16,9 @@ fetch_variable_arr:
 !:
 	// Fetch the 'coordinates'
 
+	lda FOUR6
+	pha                                          // FOUR6 might get overridden, but we'll need it
+
 	ldx #$00                                     // counts number of dimensions
 
 	// FALLTROUGH
@@ -74,6 +77,10 @@ fetch_variable_arr_check_dimensions:
 
 	bne_16 do_BAD_SUBSCRIPT_error
 
+	// Store number of dimensions, will be needed later
+
+	stx __FAC1+0
+
 	// FALLTROUGH
 
 fetch_variable_arr_calc_pos:
@@ -83,37 +90,100 @@ fetch_variable_arr_calc_pos:
 	lda #$05
 	jsr helper_VARPNT_up_A
 
-	// Set previous dimension size as '1'
+	// Set the initial offset as '0'
 
-	// XXX implement this
+	lda #$00
+	sta __FAC1+1
+	sta __FAC1+2
 
 	// FALLTROUGH
 
 fetch_variable_arr_calc_pos_loop:
 
-	// Fetch the coordinate from stack
+	// Fetch the current dimension
 
-	// XXX implement this
+	dex
+	txa
+	asl
+	tay
+
+#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
+
+	lda (VARPNT), y
+	sta __FAC1+3
+	iny
+	lda (VARPNT), y
+	sta __FAC1+4
+	iny
+
+#endif
+
+	// Multiply offset by current dimension
+
+	jsr helper_array_create_mul
+
+	// Fetch the coordinate from stack; also add it to offset
+
+	clc
+	pla
+	sta INDEX+0
+	adc __FAC1+1
+	sta __FAC1+1
+	pla
+	sta INDEX+1
+	adc __FAC1+2
+	sta __FAC1+2
 
 	// Compare current coordinate with current dimension size
 
+	// XXX
 	// XXX implement this
-
+	// XXX
-	// 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
+	cpx #$00
 	bne fetch_variable_arr_calc_pos_loop
 
+	// FALLTROUGH
+
+fetch_variable_arr_calc_pos_loop_done:
+
+	// Retrieve FOUR6, use it to calculate final offset
+
+	pla
+	sta FOUR6                          // XXX is it needed?
+	sta __FAC1+3
+	stx __FAC1+4                       // .X is 0 at this moment
+
+	jsr helper_array_create_mul
+
+	// Increment VARPNT by number of dimensions * 2, to point start of data
+
+	lda __FAC1+0
+	asl
+	jsr helper_VARPNT_up_A
+
 	// Increment VARPNT by the calculated offset and quit
 
-	// XXX implement this
+	clc
+	lda __FAC1+1
+	adc VARPNT+0
+	sta VARPNT+0
+	lda __FAC1+2
+	adc VARPNT+1
+	sta VARPNT+1
 
-	jmp do_NOT_IMPLEMENTED_error
+	rts