breaking an if loop

Question

Fred 2013-10-2

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88880-breaking-an-if-loop

评论： Fred 2013-10-2

In the following script, why doesn't the break in line 24 get executed?

clf
xx = 1:.01:2;
vec = 1:.01:2;
for i=1:101;
  yy(i)= -1*vec(i)+2 ;
end;
plot(xx,yy,'r')
plot(xx,yy);
axis ([0 10 0 2]);
hold on
N = 100;
xo = 1.8; yo = 1.2;
dx = .01; dy = .01;
for i = 1:N
  x(i) = xo - i*dx;
  y(i) = yo - i*dy;
  plot(x(i),y(i))
  for j = 1:N
      if y(i) < yy(j)&& x(i) < xx(j)
          plot (x(i),y(i),'o')
          break
      end
  end
end

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Answer 1

Andrei Bobrov 2013-10-2

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https://ww2.mathworks.cn/matlabcentral/answers/88880-breaking-an-if-loop#answer_98431

在 MATLAB Online 中打开

t = false;
for i = 1:N
     if t, break; end
     x(i) = xo - i*dx;
     y(i) = yo - i*dy;
     plot(x(i),y(i))
     for j = 1:N
         if y(i) < yy(j)&& x(i) < xx(j)
             t = true;
             plot (x(i),y(i),'o')
             break
         end
     end
end

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Answer 2

Roger Stafford 2013-10-2

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/88880-breaking-an-if-loop#answer_98432

Are you sure the 'break' is not executed? You have placed it within the inner for-loop, so when it performs the break it continues to execute the outer loop. Read Mathworks' documentation: "In nested loops, break exits only from the loop in which it occurs. Control passes to the statement that follows the end of that loop." In your case whenever you have an (i,j) pair for which i+j>81 and i-j>19 both become true, then the break should occur with no further j values for that i value. However it goes right on with the next value of i in the outer loop and this break should therefore occur repeatedly for a number of different values of i, once on each i.