Curious bug

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What is this?

Posted on 2008-07-24 22:08 By alla (

90)

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Here's a Maple bug:

If you define the function f(x) = (5 - y) ^ (4/3), then try to evaluate it at f(-3), you get the wrong answer. To get the right answer you must evaluate it at f(-3.) Of course we know that Maple distinguishes between exact answers & decimal answers, but both answers are supposed to be the same. In the first case, you get 88^(1/3); in the second, the correct answer of 16.0.

Anyone know what's going on?

Allan

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Comments

simplify

Comment on 2008-07-24 23:56 from alec ( Maple Rating 4

1470)

It is not 88^(1/3), it is 8*8^(1/3) with an invisible multiplication sign. It can be simplified to 16 using simplify.

Alec

:-)

Comment on 2008-07-25 04:54 from Axel Vogt ( Maple Rating 4

948)

one of the "advantages of the standard interface" ? Well, a bit kidding ...

asserting a bug would have had the need to use "evalf"

It's a bug

Comment on 2008-07-25 10:12 from JacquesC ( Maple Rating 4

1697)

If there is not enough space for the typical user to recognize that there is a multiplication going on, ie if the display of Maple's results will likely be mis-interpreted, then that's a plain bug. If a user cannot understand, for very simple like this, Maple's output, then Maple is useless to that user. As it is clearly Maplesoft's intent for Maple to be useful, it must be viewed as a bug.

Cube roots

Comment on 2008-07-25 16:17 from alec ( Maple Rating 4

1470)

There are 2 other things in that which could be considered as bugs as well, beside a poor display.

First - 8^(1/3) shouldn't appear in the display at all, it should be evaluated to 2, then multipled by 8 and the result should be displayed as 16.

Second - if it is displayed, it should be displayed as the cube root of 8 and not as 8 in the power 1/3.