• Feathercrown@lemmy.world
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        12 hours ago

        They do, it’s grouping those operations to say that they have the same precedence. Without them it implies you always do addition before subtraction, for example.

        • 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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            2 hours 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?

            • 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 hour 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.