string

• string.len

  a=string.len('你好嗎?')
  or
  a = #'你好嗎?'
  

• string.lower(s)

  a,b= 'anD','and'
  print (string.lower(a) == b)
  

• string.upper(s)

  a,b= 'and','AND'
  print (string.upper(a) == b)
  

• string.sub(s,i,j)

  a = 'abcdefghijk'
  print (string.sub(a,2))　
  　　　＞從第二個字元開始擷取，得：bcdefghijk
  print (string.sub(a,2,-2))
  　　　＞擷取第二個字元到倒數第二個字元，得：bcdefghij