Comment by tedsuo | Hacker News Reader

Comment by tedsuo | Hacker News Reader

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The OP's complaint about Go's type system seems to mainly be that memory allocation is explicit.

Go is always "pass by value", and it's true that I've watched developers struggle to grasp the full ramifications of what that means regarding memory usage. But not understanding the subtlety of memory allocation usually means your programs will simply run slower and consume more memory. It does not usually mean that your programs will run incorrectly.

Given that the OP mentions that they find the slower, more expensive execution of racket programs to be an acceptable trade-off, I'm surprised that they have a problem with this.

Personally, I prefer running in a language that allows me to reason about the memory allocation explicitly. I'd only prefer to give that up in favor of a declarative language that could compute the optimal execution for me. Unfortunately that language is a bit of a unicorn for general purpose programming.

In Go you can pass a pointer, and a pointer to a pointer. I understand both cases are usually called "pass-by-reference". If you call "pass-by-value" to passing a pointer, then the notion of "pass-by-value" and "pass-by-ref" are not very useful.

If what you are passing is a pointer, then the value of the pointer (an integer) is copied. So pointers are passed by value.

"Pass by reference" means that the runtime will convert what looks like an instruction to copy a value (such as a data structure) into an instruction to copy only the address. Go has no such concept. You cannot make a new value that is a "reference" to another value. If you make a new variable that takes a value, that variable allocates a new block of memory the size of that value. Assigning a value to the variable (or passing a value to a function) makes a copy of the value into the new memory address. You can make a "reference" only by explicitly making a pointer and copying the address of another object.

"Pass by reference" languages treat everything as a pointer by default, forcing you to make a copy operation when you do not want this behavior. This may seem like an equivalent programming model, and possibly simpler because this pointer business if confusing at first. However, basic concepts such as a call stack or an array of values can no longer be expressed easily, because with "pass by reference" languages you have removed the concept of a value from the language. So pass-by-reference languages can lead to confusion in large programs, even if they seem simpler at first.

Basically, go is "pass by value" because the language forces you to always be explicit about when you are copying an entire value, and when you are only copying a pointer.

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