Comment on I dunno

• SmartmanApps@programming.dev ⁨4⁩ ⁨days⁩ ago

  They do, it’s grouping those operations to say that they have the same precedence

  They don’t. It’s irrelevant that they have the same priority. MD and DM are both correct, and AS and SA are both correct.

  Without them it implies you always do addition before subtraction, for example

  And there’s absolutely nothing wrong with doing that, for example. You still always get the correct answer

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  • Feathercrown@lemmy.world ⁨3⁩ ⁨days⁩ ago

    Uh, no. I don’t think you’ve thought this through, or you’re just using (AS) without realizing it. Conversations around operator precedence can cause real differences in how expressions are evaluated and if you think everyone else is just being pedantic or is confused then you might not underatand it yourself.

    Take for example the expression 3-2+1.

    With (AS), 3-2+1 = (3-2)+1 = 1+1 = 2. This is what you would expect, since we do generally agree to evaluate addition and subtraction with the same precedence left-to-right.

    With SA, the evaluation is the same, and you get the same answer. No issue there for this expression.

    But with AS, 3-2+1 = 3-(2+1) = 3-3 = 0. So evaluating A with higher precedence rather than equal precedence yields a different answer.

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    • SmartmanApps@programming.dev ⁨3⁩ ⁨days⁩ ago

      Some other pedantic notes you may find interesting

      It’s hilarious that you added in this in afterwards, hoping I wouldn’t see it so you could claim the last word 😂

      There is no “correct answer” to an expression without defining the order of operations on that expression

      There is only one order of operations, defined in many Maths textbooks.

      Addition, subtraction, etc. are mathematical necessities that must work the way they do

      Hence the order of operations rules, found in Maths textbooks

      But PE(MD)(AS) is something we made up

      PEMDAS actually, and yes, it’s only a convention, not the rules themselves

      there is no actual reason why that must be the operator precedence rule we use

      That’s why it’s only a convention, and not a rule.

      this is what causes issues with communicating about these things.

      Nope, doesn’t cause any issues - the rules themselves are the same everywhere, and all of the different mnemonics all work

      Your second example, -1+3+2=4, actually opens up an interesting can of worms

      No it doesn’t

      so subtraction is a-b

      Just -b actually

      negation is -c

      Which is still subtraction, from 0, because every operation on the numberline starts from 0, we just don’t bother writing the zero (just like we don’t bother writing the + sign when the expression starts with an addition).

      a two-argument definition of subtraction

      Subtraction is unary operator, not binary. If you’re subtracting from another number, then that number has it’s own operator that it’s associated with (and might be an unwritten +), it’s not associated with the subtraction at all.

      you can also define -1 as a single symbol

      No you can’t. You can put it in Brackets to make it joined to the minus sign though, like in (-1)²=1, as opposed to -1²=-1

      not as a negation operation followed by a positive one

      The 1 can’t be positive if it follows a minus sign - it’s the rule of Left Associativity 😂

      Image

      These distinctions are for the most part pedantic formalities

      No, they’re just you spouting more wrong stuff 😂

      you could argue that -1+3+2 evaluated with addition having a higher precedence than subtraction is -(1+3+2) = -6

      No, you can’t. Giving addition a higher priority is +(3+2)-1=+5-1=4, as per Maths textbooks…

      Image

      Isn’t that interesting?

      No, all of it was wrong, again 😂

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    • SmartmanApps@programming.dev ⁨3⁩ ⁨days⁩ ago

      you’re just using (AS) without realizing it

      as per the textbooks 🙄

      Conversations around operator precedence can cause real differences in how expressions are evaluated

      No they can’t. The rules are universal

      you might not underatand it yourself

      says someone about to prove that they don’t understand it… 😂

      With (AS), 3-2+1 = (3-2)+1 = 1+1 = 2

      Nope! With AS 3-2+1=+(3+1)-(2)=4-2=2

      This is what you would expect

      Yes, I expected you to not understand what AS meant 😂

      since we do generally agree to evaluate addition and subtraction with the same precedence left-to-right

      It’s only a convention, not a rule, as just proven

      With SA, the evaluation is the same

      No it isn’t. With SA 3-2+1=-(2)+(3+1)=-2+4=2

      you get the same answer

      Yep, because order doesn’t matter 🙄 AS and SA both give the same answer

      No issue there for this expression

      Or any expression

      But with AS, 3-2+1 = 3-(2+1)

      You just violated the rules and changed the sign of the 1 from a + to a minus. 🙄 -(2+1)=-2-1, not -2+1. Welcome to how you got a wrong answer when you wrongly added brackets to it and mixed the different signs together

      So evaluating addition with higher precedence rather than equal precedence yields a different answer

      No it doesn’t., as already proven. 3-2+1=+(3+1)-(2)=+4-2=2, same answer 🙄

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      • Feathercrown@lemmy.world ⁨3⁩ ⁨days⁩ ago

        Oh, it’s you. I really want to have a good discussion about this, but it is not possible with your debate style. Once again, fragmenting your opponent’s argument into a million partial statements and then responding to those is ineffective for several reasons:

        1. You fail to understand the argument your opponent is making, and so you do not learn anything by engaging with it. You must first understand to learn.

        2. By divorcing each partial statement from its surrounding context, you are likely to change its meaning, so you are no longer even responding to the meaning of what was said.

        3. You are not making a point of your own, which means you are less likely to figure out your own mental model. You are simply stating facts, opinions, or misunderstandings as if they are self-evidently true, without knowing why you believe them to be true.

        4. Expanding on point three, it’s very easy to state two contradictory things without realizing it. For example, “No they can’t. The rules are universal” and “It’s only a convention, not a rule, as just proven”.

        5. Also expanding on point three, this also makes it hard for people to find the mistakes you’re making and correct them, because mistakes in your mental model are only visible through the statements you choose to make, which are incoherent when taken together. For example, I can see that you don’t fully understand what I mean by “operator precedence”, but this is not obvious from your main point, because you have no main point, because you do not understand what mine is.

        6. If your opponent also used this debate style, the argument takes hours and ends up entirely divorced from the initial meaning, completely destroying any hope of having the debate provide any actual value, ie. greater understanding.

        Please do not take these as insults; it’s a long shot to fundamentally change someone’s perspective like this in one post, but I would love if you saw the beauty of discussion.

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