Comment on I dunno

• Feathercrown@lemmy.world ⁨3⁩ ⁨days⁩ 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.

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  • SmartmanApps@programming.dev ⁨3⁩ ⁨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 ⁨2⁩ ⁨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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