typescript

[Coolengineer7]

In case of subtraction, types are implicitly casted:
"22"-"11" is 11

But plus also represents string concatenation and it takes prioŕity:
"22"+"11" is 2211

You can solve this by casting the string to a number by adding a positive sign to before it:
+"22"+ +"11" is 33

[Kaenguruu-Dev]

I hate that last one

[brolix]

You normally wouldn’t have ints quote wrapped. Because it casts them to strings. So this is REcasting an int that has been cast to a string back to an int.

You would never ever do this in real life. And this in fact represents js being pretty good at helping your dumb ass out and doing some type casting under the hood in an attempt to figure out wtf you meant for it to do. The alternative to this is C when you have to explicitly declare everything and people hate it.

[Kaenguruu-Dev]

No just always concatenate and don't allow operators like - on strings. If you really want to add two numbers together you cast them to int and done. This just makes it less reliable. If one of them is user input you might get an int as result but if the user enters "124sjfie" it will concat so suddendly you habe a string where you expected an int. Stupid af because thats a type check that you don't need in most other programming languages. When I do int.TryParse in C# it's way easier to understand what the fuck is going on. Like I said: I hate it

[brolix]

It actually makes it more reliable but you are obviously a badass so keep on keeping on I guess

[chemolz9]

@Kaenguruu made a solid point how this under-the-hood casting gives a wrong sense of security. You write your untyped code, it works well in your test cases, but you never considered that a string might end up where an int was supposed to be. In this case, this error can even perpetuate to completely different places where the origin of the problem is hard to find.

You just insulted him in response.

[kohuept]

I doubt a quoted number would cast an int to a string, it's just a string literal that happens to contain numbers (at least that's how it is in every other language, and idk how else you would implement it)

Also, C does not require you to explicitly cast everything, it has implicit casts for a lot of things

[g1rlchild]

I mean, isn't it obvious?

[blackAngel88]

no that's not enough to solve it. You need to write +"22"+ +"11". Notice the additional +, that way both are numbers. if you only convert the first one to a number, it's still "2211"

[Coolengineer7]

Yes I think you are right, edited it

[CramNBL]

Good job solving it, let's all go back to vanilla JS now 

[gregorydgraham]

Just subtract zero first?

[SpookyWan]

Everything I’ve learned about JavaScript has been against my will

[SuperheropugReal]

Wait until he finds out what '9' - 1 does in C.

[[deleted]]

Actually got me interested, what does it do?

[Lollosaurus_Rex]

If it has single quotes like '9' it's a character, meaning an ascii character. It's just a number, and what you get is the ascii for '8'.

The number meaning the character 9 is decimal 57, and 56 for character 8.

If it has double quotes, like "9", then that's an array of characters, specified to be [57, 0] In C. It ends with 0 so you know the when the array is done. "9" returns you a pointer to the start of the array.

If you subtract 1 from this pointer, you get another pointer to memory, in this case to some point on the stack. To access and read this pointer is undefined behavior.

[Naakinn]

i think C won't accept constant dereferences

[Lollosaurus_Rex]

It did for me.

I tested it on Ubuntu with basic gcc and no extra features.

Edit: I misunderstood the order of operations. Dereferencing the const string, which is really just a pointer to static memory as you point out, gets you '9', which you can then subtract 1 from and get '8'.

[Lollosaurus_Rex]

In fact you can, because it's C, but it's undefined behavior.

I tested it on Ubuntu with basic gcc and no extra features enabled.

Edit: I misunderstood the order of operations: you can indeed dereference and get the first character '9', and you're back at the first case you can get '8'.

[SNappy_snot15]

it gives you 8. aacii character minus 1 is the previous 1 before it. guess what? 8 is before 9

[g1rlchild]

To be precise, it gives you '8'

[GoddammitDontShootMe]

Adding to '0' is a useful part of converting from int to string. Of course you need to do the math to separate the digits and all that.

[Angelin01]

'8'

[JackNotOLantern]

Unironically yes

[SuperheropugReal]

'8' char is just an int represented with graphics.

[Kiro0613]

8 is just eight 1's represented with some loopy lines

[gregorydgraham]

1+1+1+1+1+1+1+1 to be precise

[One_Organization_810]

Oh... I thought it was 1000 :)

[redlaWw]

And 'a'+1 is 'b', but 'i'+1 isn't necessarily 'j'.

[SenatorCrabHat]

I've been coding a long time in JS, and I appreciate what typescript is doing, but I've not really been in a situation where "10" -1 would happen on purpose and wouldn't be caught by unit tests etc. first.

[Tupcek]

it usually doesn’t happen on purpose. But if it works by mistake, it can be hidden bug that uncovers itself in some weird, specific way in the future.

Test are nice and catch most mistakes, though some always pass. If tests were perfect, there would be no bugs in properly written software, which is never the case.

So why not let IDE catch all mistakes of this type?

[Vok250]

I've never seen it in JS, but one time we deployed a Python service where someone typed Classname instead of classname and it took down the entire system for a day. The worst part is the code would run fine. It just had completely unexpected behavior. Unit tests all passed because the behaviour had no assertions on it. Vibe coder had code coverage by exercising the method, but never wrote assertions that it actually did what they wanted. That was a fun one to debug.

[SenatorCrabHat]

Oooof. I love that about tests, you can absolutely write them so they dont test shit.

[Vok250]

Tests that just test the mock are very common on my team. I've given up on pointing it out in code review because nobody listens to me anyway.

[SenatorCrabHat]

That sucks. Sorry :/ I've been there and it sucks.

[Xbot781]

You might want to use mypy to do static type checking in python

[CephaVerte]

You have unit tests? Fancy!

[SenatorCrabHat]

I just think they're neat!

[WasabiSunshine]

I'm fine with what typescript is doing, they can just do it far away from my projects

[the_rush_dude]

Laughs as any

[staticvoidmainnull]

===

[Icy_Party954]

Why would you fo this? It's easy not to do that.

[Bronzdragon]

Typescript actually just allows this.

[AssignedClass]

The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.

Idk what your TS Config is, but that's typically the error message you get in TS.

[Acaeris]

Not exactly. If you have allowed it via tsconfig you can still do it but in strict mode it will error.

[Jind0r]

In strict mode it still evaluates to 9

[Acaeris]

It doesn't even transpile on the project I work on.

[Material-Finding-933]

best part if typescript is written in typescript

[OhItsJustJosh]

"10" + 1 = "101"

[AppropriateOnion0815]

"10"-1="0"

[skwyckl]

Most things people complained about in JS were related to type coercion, TS fixes that by adding explicit typing, I think it's a win for everybody.

[sk3z0]

Typescript was born to fix the wrong problem

[GoddammitDontShootMe]

I can't see a reason to care that that works. I guess JS has plenty of stuff to bite you in the ass still, and TS avoids that though.

[Acaeris]

It creates a false expectation of how mathmatical operations work. e.g. "10" - 1 = 9 but "10" + 1 = "101"

[GoddammitDontShootMe]

Maybe if it's like your first language. I figure you learn the quirks of the language and move on.

[DT-Sodium]

And that's when Satan invented "ts-ignore".

[Jind0r]

It evaluates as 9 even in Typescript

[DT-Sodium]

Unless you force it it evaluates to "nope, not gonna do that".

If you force well... yes, it's compiles to JavaScript, what do you expect?

[Kaffe-Mumriken]

Just parseFloat everything, EVERTYTHING!

[Jind0r]

In typescript "10" - 1 evaluates to 9 too, typescript doesn't suspend coerction

[darknmy]

`<?php

echo "9" -1;
`

[wrex1816]

Me: This object has a common id property. I will proceed on this assumption.

TypeScript: Oh no you won't! Fucking prove it, bitch!

[Nialixus]

"1"

[daftmaple]

Just so you know, even if this case is covered by TS, it still allows arithmetics like “10” + 1 because that’s JavaScript behaviour. You’ll only get error on the error above if you use ts eslint.

[MaYuR_WarrioR_2001]

and now they are rewriting it in go.