separated commands from functions

c64/basic/basic_operators/oper_add.s

@@ -0,0 +1,72 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+
+oper_add:
+
+	// This operator can be used either with two strings, or with two floats
+	// First check whether arguments match and then choose the variant
+
+	pla
+	cmp VALTYP
+	bne_16 do_TYPE_MISMATCH_error
+
+	lda VALTYP
+	bmi oper_add_strings
+
+	// FALLTROUGH
+
+oper_add_floats:
+
+	// XXX implement this
+
+	jmp do_NOT_IMPLEMENTED_error
+
+oper_add_strings:
+
+	// Retrieve string address
+
+	pla
+	sta __FAC2+2
+	pla
+	sta __FAC2+1
+
+	// Pull string length
+
+	pla
+	sta __FAC2+0
+	beq oper_add_strings_end           // if string 2 is empty, we have nothing to do
+
+	// If string 1 is empty, just copy the metadata
+
+	lda __FAC1+0
+	bne !+
+
+	lda __FAC2+0
+	sta __FAC1+0
+	lda __FAC2+1
+	sta __FAC1+1
+	lda __FAC2+2
+	sta __FAC1+2
+
+	jmp FRMEVL_continue
+!:
+	// Allocate memory for concatenated string
+
+	clc
+	adc __FAC2+0
+	bcs_16 do_STRING_TOO_LONG_error
+
+	jsr alloc_temp_string
+
+.break
+
+
+
+	// XXX finish the implementation
+
+
+oper_add_strings_end:
+
+	jmp FRMEVL_continue