Nested if statements under for loop

I have this nested if statements under a for loop. I want the for loop to calculate 3.1*5^2. And if the answer is 77.5, it should solve 3.1*3^2. Also if that equals 27.9. It should stop the for loop. But it seems to continue. Please help.

clc
A=['3' '.' '1' '*' '^' '2']
for n=0:length(A)
    try
    d=[A(1:n) '5' A(n+1:end)]
    c=eval(d)
    if c==77.5
        e=[A(1:n) '3' A(n+1:end)]
        j=eval(e)
        if j==27.9
        return
        end
    end
    end
end

[Rik]

You should compare to a tolerance. (i.e. abs(value-target)<=tol;)

You should also remove those eval calls.

Answer 1

[Awais Saeed]

eval(e) will never be equal to 27.9. To know the reason you have to set the output format from short(default) to long. After doing

format long

you will see that

eval(e) = 27.900000000000002

The workaround would be to remove unwanted numbers after decimal point and then compare. This is how I did it

clc
A=['3' '.' '1' '*' '^' '2']
for n=0:length(A)
    try
        d=[A(1:n) '5' A(n+1:end)]
        c=eval(d)
        if c==77.5
            e=[A(1:n) '3' A(n+1:end)]
            j=eval(e)
            S = sprintf('%f',j);       % convert it to string
            [idx,~]=regexp(S,'[.]');   % search for decimal point
            S(idx+2:end) = [];         % delete everything from idx+2 till end
            if isequal(S,'27.9')       % compare S (modified eval(e)) with '27.9' char
                return
            end
        end
    end
end