How can I replicate the strtrim function?

I am trying to replicate the strtrim function, but I cannot seem the figure out how to get it to work properly. When I run my code, it takes every single space (or tab) out of the string. I cannot figure out how to make it take only the leading and trailing spaces out. I know the strtrim function can do that, but I am trying to replicate that function. A detailed explanation of the solution would be much appreciated. Thank you all.

a = ' some words with   spaces  ';
k=1;
while k <= length(a)
    if a(k) == char(32)
        a(k) = '';
        k = k+1;
    elseif a(k) == char(9)
        a(k) = '';
    else
        k = k+1;
    end
end

Answer 1

[Star Strider]

You can do it with a relatively simple regexp call:

a = ' some words with   spaces  ';
[s, e] = regexp(a, '\S*');
Result = a(s(1):e(end))

Result =
some words with   spaces

[Kevin Steerman]

What if I were to do an sprintf call with a tab at the front, and I want the tab to stay?

if true
  a = sprintf('\tsome words with  spaces   ');
  %Desired_Outcome = sprintf('\tsome words with spaces');
end

[Star Strider]

It’s probably possible to do that with regexp, but it’s eluding me. I can get regexp to do some of it but not all of it at once.

[Walter Roberson]

Result = regexprep(a, {'^ +', '\s+$'}, {'', ''})

Answer 2

[Walter Roberson]

Hint: when you are removing something from a matrix in a loop, always start from the end and move to the beginning. Think of it like Tetris and "falling down" into vacated slots...