• 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. 2+3-1=4 is correct, -1+3+2=4 is 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 🙄

    • Feathercrown@lemmy.world
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      1 day 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 addition with higher precedence rather than equal precedence yields a different answer.

      =====

      Some other pedantic notes you may find interesting:

      There is no “correct answer” to an expression without defining the order of operations on that expression. Addition, subtraction, etc. are mathematical necessities that must work the way they do. But PE(MD)(AS) is something we made up; there is no actual reason why that must be the operator precedence rule we use, and this is what causes issues with communicating about these things. People don’t realize that writing mathematical expressions out using operator symbols and applying PE(MD)(AS) to evaluate that expression is a choice, an arbitrary decision we made, rather than something fundamental like most everything else they were taught in math class. See also Reverse Polish Notation.

      Your second example, -1+3+2=4, actually opens up an interesting can of worms. Is negation a different operation than subtraction? You can define it that way. Some people do this, with a smaller, slightly higher subtraction sign before a number indicating negation. Formal definitions sometimes do this too, because operators typically have a set number of arguments, so subtraction is a-b and negation is -c. This avoids issues with expressions starting with a negative number being technically invalid for a two-argument definition of subtraction. Alternatively, you can also define -1 as a single symbol that indicates negative one, not as a negation operation followed by a positive one. These distinctions are for the most part pedantic formalities, but without them you could argue that -1+3+2 evaluated with addition having a higher precedence than subtraction is -(1+3+2) = -6. Defining negation as a separate operation with higher precedence than addition or subtraction, or just saying it’s subtraction and all subtraction has higher prexedence than addition, or saying that -1 is a single symbol, all instead give you your expected answer of 4. Isn’t that interesting?

      • 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 😂

        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…

        Isn’t that interesting?

        No, all of it was wrong, again 😂

      • Feathercrown@lemmy.world
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        1 day ago

        I’m honestly disappointed that you just downvoted and left. Challenging your beliefs with contrary ideas is the only way to improve them and understand the world in a more comprehensive and accurate way.

      • 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 🙄

        • Feathercrown@lemmy.world
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          1 day 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. To bring it back to your original comment:

          Those Brackets don’t matter. I don’t know why people insist it does

          Understanding the purpose and methods of debate allows you to understand why people know the brackets matter.

          • I really want to have a good discussion about this

            says person who deleted their previous post when I proved how wrong it was 😂

            it is not possible with your debate style

            There’s no debate - the rules are in Maths textbooks, which you want to pretend don’t exist

            You fail to understand the argument your opponent is making

            You haven’t got one. That’s why you keep pretending Maths textbooks don’t exist

            By divorcing each partial statement from its surrounding context

            says person who deleted one of their posts to remove the context. 😂 The context is the rules of Maths, in case you needed to be reminded 😂

            you are likely to change its meaning

            Nope. I’m still talking about the rules of Maths 😂

            You are not making a point of your own

            Ok, so here you are admitting to comprehension problems. Which part did you not understand in addition and subtraction can be done in any order? 😂

            You are simply stating facts, opinions, or misunderstandings as if they are self-evidently true

            You left out backing it up with textbook screenshots and worked examples 😂

            without knowing why you believe them to be true.

            There’s no belief involved. It’s easy enough to prove it yourself by doing the Maths 😂

            it’s very easy to state two contradictory things without realizing it

            And yet I never have. Why do you think that is? 😂

            “No they can’t. The rules are universal”

            Which is correct

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

            Which is also correct, and in no way contradicts the previous point, and I have no idea why you think it does! 😂 The first point is about the rules, and the second point is about conventions, which isn’t even the same thing

            this also makes it hard for people to find the mistakes

            That’s because I’m not making any 😂

            I can see that you don’t fully understand what I mean by “operator precedence”

            Says person who in their other post claimed “addition first” for -1+3+2 is -(1+3+2) = -6, and not +(3+2)-1=4 😂

            If your opponent also used this debate style,

            Which you don’t, given you have no evidence whatsoever to back up your points with 😂

            ends up entirely divorced from the initial meaning

            I’ve been on-point the whole time, and you keep trying to deflect from how wrong your statements are 😂

            Please do not take these as insults

            Well, obviously not, given I just proved they were all wrong 😂

            allows you to understand why people know the brackets matter.

            Except I’ve proven, repeatedly, that they don’t, and so now you’re trying to deflect from that (and deleted one of your posts to hide the evidence of how wrong you are) 😂

            • Feathercrown@lemmy.world
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              10 hours ago

              I’m falling for the troll here but I feel compelled to point out that you did NOT read the post I deleted lmao. I deleted it because I posted it before you “responded” to my points. Go check it out, I just restored it.

              I should clarify that I haven’t responded to your “points” because there is nothing worth responding to. Your arguments can all be debunked by reading https://en.wikipedia.org/wiki/Order_of_operations, so I didn’t bother doing it myself.

              To avoid any further temptation to respond I will be blocking you. Your absence from my future will be greatly appreciated. I feel that the deleted post is in itself a very good final word to this disappointment of a “conversation” even if it is not entirely accurate. Goodbye.

              • I’m falling for the troll here

                Just as well for you I’ve provided all the necessary evidence to prove them wrong then

                I’m honestly disappointed that you just downvoted and left

                BWAHAHAHAHAHA! I DIDN’T leave, quite demonstrably.

                Challenging your beliefs with contrary ideas is the only way to improve them and understand the world in a more comprehensive and accurate way

                So how come you won’t then?

                I should clarify that I haven’t responded to your “points” because there is nothing worth responding to

                In other words, you have been proven wrong by them

                Your arguments can all be debunked by reading https://en.wikipedia.org/wiki/Order_of_operations

                Wikipedia can be comprehensively debunked by MATHS TEXTBOOKS - you know, those things you refuse to look at because they prove you are wrong 😂

                I didn’t bother doing it myself.

                So in other words, Wikipedia is all you had, and, having been disproven by Maths textbooks, you’ve got nothing

                I will be blocking you

                An admission of defeat then

                I feel that the deleted post is in itself a very good final word to this disappointment of a “conversation”

                Feel free to unblock me when you’re ready to take your own advice

                if it is not entirely accurate

                Just like all your other posts then

                Goodbye

                Don’t let the door hit you on the way out