What happen to this loop?

a=0
t=1
while t==1
    a=a+0.01
    if a == 0.5
        t=0
    end
    
end    

%why it only break loop when a=a+0.1

Answer 1

[Torsten]

a=0;
t=1;
while t==1
    a=a+0.01;
    if a >= 0.5
        t=0;
    end
end    
a

a = 0.5000

t

t = 0

%why it only break loop when a=a+0.1

[Allen Wei]

i mean when i type a=a+0.1

t will become 0 and the loop breaks

but when a=a+0.01 loop can't break

is my matlab bugged or what happened?

[Torsten]

a will not exactly become 0.5 because of floating point arithmetic. That's why statements as

if a == 0.5

are dangerous because they are almost never true.

Use

if a >= 0.5

to leave the while-loop as I did above.

[Allen Wei]

i see

thank you so much

Answer 2

[Image Analyst]

See the FAQ

https://matlab.fandom.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_(or_similar)_not_equal_to_zero?

If you want, you can use >= instead of == or use ismembertol

[Allen Wei]

appreciate that