Change-Case-of-String.gdl

!--- Change the Case of a String in GDL ---!
! Go to https://github.com/runxel/GDL-playground for more.

!>>> Conversion/Replacement String
dim UPlo[2]
UPlo[1] = "abcdefghijklmnopqrstuvwxyzàáâăãäåæąćçčçðďèéêëęìíîïłľĺńňñóôőöõøŕřůùúűüýþßśšşťţźžż"
UPlo[2] = "ABCDEFGHIJKLMNOPQRSTUVWXYZÀÁÂĂÃÄÅÆĄĆÇČÇÐĎÈÉÊËĘÌÍÎÏŁĽĹŃŇÑÓÔŐÖÕØŔŘŮÙÚŰÜÝÞߌŠŞŤŢŹŽŻ"

make_uppercase = 0
make_lowercase = 1

!>>> Example
txt = "a TeSt StRInG, wITh ÜmLäUtE aND $PeCiAL cH4ars!?"  : print txt
_case = make_uppercase : gosub "ChangeCase"               : print txt
_case = make_lowercase : gosub "ChangeCase"               : print txt

END !---END---END---END---END---END---END---END---END---END---END---END---!

"ChangeCase":
    str_len = strlen(txt)
    for i=1 to str_len
        _s = strstr(UPlo[2-_case], strsub(txt, i, 1))
        if _s then 
            txt = strsub(txt, 1, i-1) + strsub(UPlo[1+_case], _s, 1) + strsub(txt, i+1, str_len-i)
        endif
    next i
return