[naasking]

In that case, add a type that constrains the values to the expected user inputs. Now not only are you passing the type checking, you're strongly enforced this invariant at the point where it makes the most sense, you've future-proofed this code against possible future misuse where the expected inputs might change, and you've made the code essentially self-documenting.

[ReflectedImage]

I'm not sure many languages support the introduction of types such as:

* An integer that is sum of two primes.

* A string that is created between the hours of 2 pm - 4 pm on a Tuesday.

* A dictionary who's fields comprise a valid tax return.

What do you mean by future proving? If the new version of the code doesn't ship by 2 pm today, the company goes bankrupt and there is no future for the code.

[naasking]

> I'm not sure many languages support the introduction of types such as:

Any language with types can enforce any proposition you can reliably check, which you run as part of the type's constructor. There are multiple ways to do this, for instance in pseudo-ML:

> * An integer that is sum of two primes.

    type SumOfPrimes
    fn sumOfPrimes : Prime -> Prime -> SumOfPrimes
    type Prime
    fn primeOfInt : Int -> Maybe Prime

> * A string that is created between the hours of 2 pm - 4 pm on a Tuesday.

    type Tuesday2To4String
    fn whichString : Clock -> String -> Either String Tuesday2To4String

> * A dictionary who's fields comprise a valid tax return.

    type ValidTaxReturn
    fn checkTaxReturn : Dictionary String String -> Maybe ValidTaxReturn

> What do you mean by future proving? If the new version of the code doesn't ship by 2 pm today, the company goes bankrupt and there is no future for the code.

Shipping broken code will not save the company from bankruptcy. It's also a myth that dynamically typed languages will get your code out faster.

[ReflectedImage]

I'm not sure how you intend to check the creation date of a string in memory since there is no information available to do that or that a tax return is valid given the thousands of rules involved.

Nevertheless let's move on.

It's not a myth, if you are using dynamic typing you will get three times the number of features out the door as someone who uses static typing.

It's just a fact.

1 dynamic typed programmer = 3 static typed programmers in productivity and output.

That is why people use dynamic typing.

From a commerical perspective, static typing does not make sense in most cases. You need something more than a typical business CRUD app to justify it. Usually you only need static typing for performance reasons. Like for a video game or image processing.

In practice, the shipped code doesn't have noticably more bugs. That just something which people who have never used dynamic typing properly like to believe.

If you ever read an article by Eve online where they say Python is their secret weapon or watched what Discord did by implementing everything in Python first. You will understand.

[int_19h]

People use dynamic typing less and less, though. JavaScript and Python are the two most prominent dynamically typed languages in the industry, and what do we have there? Most JS developers love TypeScript, and Python bolted on type annotations in the core language (and libraries are generally following suit).

With that in mind, your other claims like the 1:3 ratio really need very solid sources to be taken seriously.

[ReflectedImage]

I had a job for 2 years where I had the write the same program in both a dynamically typed language and a statically typed language around every week.

On Monday morning, I wrote the dynamic typed version of the program. Then until Thursday afternoon wrote the statically typed version of the program. Then the rest of the week was writing tests that compare the output of both versions of the program.

After 2 years of doing it, I think I would know. If that sounds weird to you, it's called Prototyping, shocking that someone might prototype something in a scripting language designed for prototyping, I know.

The two classic examples are Eve Online with their "Python is our secret weapon". They used Python to out develop their competition. The other example is Discord who used Python to get to market quickly. Then they used Rust to reduce their operating costs by increasing the code's performance.

Python adding type annotations is an unfortunate problem associated with too many people coming in from statically typed languages. The problem with success and all that.

Statically typed Python codebases tend to be awful because the developers don't realise that they need to break the codebase down into smaller programs.

JavaScript is not a very good language due to the way it was designed and built and pretty much anything is an improvement to it.

[naasking]

> I'm not sure how you intend to check the creation date of a string in memory since there is no information available to do that

See the signature of the constructor function I provided.

> or that a tax return is valid given the thousands of rules involved.

Tax software does it every year. Clearly the government has an effective procedure to decide the validity of a tax return, even if that procedure is executed by a human.

> It's not a myth, if you are using dynamic typing you will get three times the number of features out the door as someone who uses static typing. It's just a fact.

That's just laughably false. There is zero empirical evidence supporting this claim.

> In practice, the shipped code doesn't have noticably more bugs. That just something which people who have never used dynamic typing properly like to believe.

No True Scotsman fallacy.

[ReflectedImage]

A signature of a function is very different from it's implementation.

"That's just laughably false. There is zero empirical evidence supporting this claim."

There is a reason all the startups are using Python. Just ask Eve Online or Discord. Dynamic typing is great for getting products to market fast.

Neither of them have problems with too many bugs. What you are saying doesn't even make sense, since you would just increase your QA budget if it increased the rate of bugs. So how in earth could the end user see more bugs?

Dynamic typing has an issue but that issue is code performance. Eve Online gets slow downs during massive battles and Discord rewrote parts of their interface in Rust to save on server costs.

[naasking]

> There is a reason all the startups are using Python.

Show the evidence that "all the startups" are using Python.

[lliamander]

That is the correct end state, but there can be practical considerations for why you might want to run (and possibly even release) the software in this partially correct state, and fix the edge cases later.

[naasking]

I don't disagree, but most statically typed languages don't enforce a level of correctness where this would be an issue. We're not programming with theorem provers with an elaborate specification.

I somewhat agree with your point #2 which is why Haskell provides a deferred type checking mode for prototyping purposes[1]. I think this should be more common among typed languages, but this is not a very typical scenario either.

[1] https://downloads.haskell.org/ghc/latest/docs/users_guide/ex...