Replacing a for loop with a while loop

Question

I have written a function that estimates the inverse of e and loops through values of n until the approximated value is within a given tolerance of the actual value.

Currently I use this code:

function [approx, n] = calc_e(tolerance)

for n = 1:inf
    approx = ((1-1/n)^n);
    diff = (1/exp(1)) - approx;
    if diff < tolerance, break; end
end
end

This works fine however I have been told that it could be more efficient by using a while loop but I can't work out how to do it in that way.

Can anybody shed some light on this?

furthermore, the name of the func is missleading, you are approximating 1/e, not e (which would require (1+1/n)^n — lejlot
– lejlot, Commented Nov 17, 2015 at 16:08
You really should avoid using built-in functions names like diff as variable names. — beaker
– beaker, Commented Nov 17, 2015 at 16:13

houtanb · Accepted Answer · 2015-11-17 16:10:31Z

4

Simply do:

function [approx, n] = calc_e(tolerance)
n = 1;
while (1/exp(1)) - ((1-1/n)^n) >= tolerance
   n = n + 1;
end
end

edited Nov 17, 2015 at 16:10

answered Nov 17, 2015 at 16:06

houtanb

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2 Comments

lejlot Over a year ago

you forgot about n ... initializing, incrementing

lejlot Over a year ago

actually you can stil have a one-liner, you can put expression for diff inside while condition and increment in the body

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