vardef isbetween(expr a, i, f) =
  if string a:
    if (ASCII(a) >= ASCII(i)) and (ASCII(a) <= ASCII(f)):
      true
    else:
      false
    fi
  else:
    false
  fi enddef;

vardef toupper(expr s) =
  save ?; string ?; ? := ""; d := ASCII"A" - ASCII"a";
  for i = 0 upto length(s)-1:
    if isbetween(substring(i, i+1) of s, "a", "z"):
      ? := ? & char(ASCII(substring(i,i+1) of s) + d)
    else:
      ? := ? & substring(i, i+1) of s
    fi;
  endfor
  ?
enddef;

vardef tolower(expr s) =
  save ?; string ?; ? := ""; d := ASCII"a" - ASCII"A";
  for i = 0 upto length(s)-1:
    if isbetween(substring(i, i+1) of s, "A", "Z"):
      ? := ? & char(ASCII(substring(i,i+1) of s) + d)
    else:
      ? := ? & substring(i, i+1) of s
    fi;
  endfor
  ?
enddef;