用scl编程调用FC20，输出的数据类型为字符串，但是程序中没有反馈值，请各位大侠指点

LEFT or RIGHT

The LEFT and RIGHT functions (FC20 and FC32) return the first or last L characters of a string. If L is higher than the current length of the STRING variable, the complete string is returned. If L = 0, an empty string is returned. If L is negative, an empty string is output.