在切片上调用len（）有多快？

Question

I am wondering how fast is it to access len() of a slice. If I need to use the length of a slice for a few time, is it worthwhile to store it to an int variable? Or calling len() will be optimized as if an int variable is accessed? (In such case, there is no need to store the length of a variable by the user.) Thanks.

Answer 1

Here is my understanding:

You can regard slice as a struct,of which length is a member.

The only thing function len() does is to read that member of type slice struct,thus there is no need to worry about its performance---it's as fast as reading the length int you create by yourself.