Why can’t we access string.len directly if a string is internally {header *ptr, len int}?

[BoubkerElmaayouf]

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if a "string" is a struct of {header *ptr, len int}; why not allow the use of the var string.len

[chokiproai]

In many programming languages (like Go), a string is internally represented as a struct with a pointer to the data and a length, e.g., {ptr *byte, len int}. However, you cannot access string.len directly for a few important reasons:

Encapsulation / Abstraction:

The language designers want the internal representation to be hidden. Exposing len directly would tie your code to the implementation details, which might change in future versions.

By using a function like len(s) instead, the language can safely change the internal layout without breaking existing code.

Immutability and safety:

Strings are often immutable. Allowing direct access to len might tempt someone to modify it, which could lead to memory corruption or inconsistencies with the actual data.

Uniformity and flexibility:

Providing a function (len(s)) lets the language implement additional checks or optimizations behind the scenes. For example, some languages may optimize string storage differently (small string optimizations, rope strings, etc.), and len(s) abstracts that complexity.

[BoubkerElmaayouf]

Good points. The big reason is that exposing s.len would lock in the string’s internal layout forever. Using len(s) keeps the representation flexible so the compiler/runtime can change it later (optimizations, small-string storage, etc.) without breaking code.

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