simple point function seems strange

> Hi
>
> (10@20) rotateBy: #left centerAt: 0 @0
> returns
> 20@ -10
>
> and my math tells me that this is a rotation to the right.
>
> Am I correct?
> Then why I'm wrong? screen coordinates vs. math coordinate?
>
> Stef

>  On 08.07.2010 00:11, Stéphane Ducasse wrote:
>> Hi
>>
>> (10@20) rotateBy: #left centerAt: 0 @0
>>     returns
>>         20@ -10
>>
>> and my math tells me that this is a rotation to the right.
>>
>> Am I correct?
>> Then why I'm wrong? screen coordinates vs. math coordinate?
>>
>> Stef
> You rotate around the center, left is compared to the center ->  point
> vector, not the other way around.
>
> Cheers,
> Henry

> On 08.07.2010 00:26, Henrik Sperre Johansen wrote:
>> On 08.07.2010 00:11, Stéphane Ducasse wrote:
>>> Hi
>>>
>>> (10@20) rotateBy: #left centerAt: 0 @0
>>>    returns
>>>        20@ -10
>>>
>>> and my math tells me that this is a rotation to the right.
>>>
>>> Am I correct?
>>> Then why I'm wrong? screen coordinates vs. math coordinate?
>>>
>>> Stef
>> You rotate around the center, left is compared to the center ->  point vector, not the other way around.

>>
>> Cheers,
>> Henry
> ... assuming you use screen coordinates of course, starting at top left :)
>
>
>
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