SQLite scalar function example

square.c

static void square (sqlite3_context *ctx, int argc, sqlite3_value **argv) {
	int type = sqlite3_value_type(argv[0]);
	double d = sqlite3_value_double(argv[0]);	
	
	switch (type) {
		case SQLITE_NULL:
			sqlite3_result_null(ctx);
			break;
			
		case SQLITE_INTEGER:			
		case SQLITE_FLOAT:		
			sqlite3_result_double(ctx, d * d);		
			break;
			
		case SQLITE_TEXT:			
		case SQLITE_BLOB:	
			sqlite3_result_error(ctx, "Unsupported", -1);					
			break;
			
		default:
			sqlite3_result_error(ctx, "Impossible", -1);
	}
}