# Finding odd and even values without functions

조회 수: 15(최근 30일)
Jose Grimaldo 1 Apr 2020
편집: John D'Errico 5 Apr 2020
Is it possible to identify if a value is even or odd using for loops instead of using a function (Ex. mod)? If possible, can someone show me?

#### 댓글 수: 2

James Tursa 2 Apr 2020
What have you done so far? What specific problems are you having with your code?
Jose Grimaldo 2 Apr 2020
Im trying to separate evenly the array into two variables. The odd index and the even index using for loops. Cant figure it out.
A= % 8x1 array
[r,c]=size(A)
BA=A(1)
CA=A(2)
for i=1:r-1
BA(i+1)=A(i+2)
BC(i+1)=B(i+1)
end

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### 채택된 답변

darova 2 Apr 2020
while 1
a = a/2;
if abs(a-1) < 0.01 % if very close to '1'
disp('even')
break;
elseif a < 1 % if smaller than '1'
disp('odd')
break;
end
end

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### 추가 답변(2개)

per isakson 2 Apr 2020
Try this
>> a=1:12
a =
1 2 3 4 5 6 7 8 9 10 11 12
>> (-1).^[a]==1
ans =
1×12 logical array
0 1 0 1 0 1 0 1 0 1 0 1
>> (-1).^[-a]==1
ans =
1×12 logical array
0 1 0 1 0 1 0 1 0 1 0 1
>> (-1).^[1e9+a]==1
ans =
1×12 logical array
0 1 0 1 0 1 0 1 0 1 0 1
>>

#### 댓글 수: 4

표시 이전 댓글 수: 1
per isakson 3 Apr 2020
even and odd implies whole numbers. Whole numbers are by default implemented as flint, floating point integers. I don't think that "floating point precision error" will be a problem here.
darova 3 Apr 2020
Agree. It was just late. Don't know why i asked it
per isakson 5 Apr 2020
Better safe than sorry; one should be sceptical to the combination of double and ==.

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John D'Errico 5 Apr 2020
편집: John D'Errico 5 Apr 2020
A = 1:10;
A == fix(A/2)*2
ans =
1×10 logical array
0 1 0 1 0 1 0 1 0 1
As long as A is composed of integers, this will suffice as a test for even-ness. Yes, I know that is not a word. How about parity instead? ;-) For non-integers of course the concept of even and odd is meaningless.
However, when the target is itself an integer class, then you can be slightly more concise, as the fix is no longer needed. The divide by 2 automatically truncates the fractional part implicitly, casting the division into an integer.
A = uint8(1:10);
A == A/2*2
ans =
1×10 logical array
0 1 0 1 0 1 0 1 0 1

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