Extracting unique elements of a string

[anna halewska]

Dear Statalisters,

I have a string variable containing letters seperated by the ";" sign. Here are a few rows:

code
L; O; O
F; F; F
E
H; H; O

I would like to keep only one copy of each letter. Here is the desired result for the example above:

code_new
L; O
F
E
H; O

I can work around absence of spaces for the semicolon sign, I just want to get rid of duplicates inside the string.

Thank you in advance for your help.

[daniel klein]

Here is a brute-force approach, based on the example

generate code_new = code

forvalues i = 1/`=c(N)' {
    
    local line = subinstr(code[`i'],";"," ",.)
    
    local line : list uniq line
    
    replace code_new = subinstr("`line'"," ","; ",.) in `i'
    
}