What are generics?0
Generics allow for less code, thus they are easier to debug, test and reason about. I've used them a lot in C++ and I do miss them in Go. It's not a deal breaker for me either way, but for people who write larger, more complex code, not having them makes it more difficult (more code to write, test and maintain).
C does not have generics either. Go is a lot like C in this regard.
And no, being a dynamic language is not what makes Python slow. Lua, Nim and Scheme are all examples of dynamic languages with fast implementations.
- Yes, being a dynamic language slows it down a lot. For example, when evaluating a+b, the interpreter has to check the types of the variables a and b at runtime beform performing the right form of addition (it might be an int, or a string, you dont know). Even with JIT (just in time compilation) the compiler has to initially “guess” that the variables are numbers, and fall back if that is not the case. Statically typed languages do not have this problem, because you know the types of variables beforehand at compile time.
By the way, Nim is not a dynamic language. And LuaJIT is one of the the fastest dynamic language implementations because the language is very simplistic (compared to Javascript/Python/Ruby) and Mike Pall is a robot from the future...
That's not necessarily true. In Scheme, a very dynamic language, the compiler will generally make choices about memory layout of the various values before launching into the evaluation phase. Where safe or possible to do so, it will probably reduce the number of choices that will have to be made at runtime, at compile time. The interpreter may not have to lookup what the data type is, because it may just have two bits of memory and an instruction to call. You can know what the data will be, and optimise for it. [0]
There's no reason that: b = 1; c = 2; a = a + b needs to be slower than a = 1 + 2 if b and c are never referenced before or after. But in Python, it is, because the design makes it harder to know whether or not an object should get optimised away.
> And LuaJIT is one of the the fastest dynamic language implementations because the language is very simplistic
Right, Lua is dynamic, and one of the design choices was making it simple, and so it's easier to make it faster.
[0] https://www.youtube.com/watch?v=2Op3QLzMgSY&list=PLE18841CAB...
[1] https://www.amazon.com/Structure-Interpretation-Computer-Pro...
Some of it is simple stuff, like CPython being interpreted, so PyPy get's a huge boost by JITting.
Some of it is much harder stuff, like the way Python is designed to store objects in memory (a list is a pointer to a contiguous space of pointers to things that might be pointers...), and everything that hangs off each object (everything has a dict), and the awful GIL ([0]). Awful for performance, great for thread-safety.
Every single part of a language design has trade-offs. It depends on what you're trying to do whether or not they help you, or hinder you.
Sometimes you change how you're doing things because priorities change, and get a radical improvement, like Python's 3.6 Dict. Most of the time, you don't. One step at a time. Not being able to break backwards compatibility hinders the designer, if they realise a trade-off they've made was a mistake. So you get stuck with some features you'd rather not have.
To be sure, the internal implementation of CPython (the only one I'm familiar with) is complicated as hell. But it's a whole lot simpler than any fast JavaScript runtime I've ever used. I think that's the result of a conscious choice by the maintainers/BDFL/community in Python, not a side effect of it having less funding (assuming that's the case).
This could be my naïveté, but I don’t see why generics in Go couldn’t work analogously to the way they do in TypeScript, just a way for the compiler to verify the correctness of code accessing an interface{}.
Without generics, if you need a list filled with TPS Reports you basically have 2 choices:
- Use the 'untyped' List that deals with objects. You will have to cast to TPS whenever you look up an item and you will have to make sure that no one accidentally adds a Timesheet to this list.
- Write a custom TpsReportList. I'm sure you'll be able to write an implementation as efficient as the language creators. Oh an if you copy and past from TimesheetList, don't forget to check all names. `tpsReports.AddTimesheet()` is just embarrassing.
With generics, you will have a `List<T>` type. If you need a list of TPS Reports you will use the type `List<TpsReport>`. If you need a list of Timesheets, you will use `List<Timesheet>`.
You can't add the wrong type of item to such a list, you will always get the declared item from that list and you can't assign an instance of one type to a variable of the other type.