在GHCi中，如何键入不在函数定义内的保护方程式？

Question

在GHCi中，如何键入在函数定义之外使用的保护方程式？

我什么时候不能

Prelude> c | False == True  = 0 | otherwise = 1

<interactive>:28:26: error:
    • Could not deduce (Num Bool) arising from a use of ‘otherwise’
      from the context: Num t
        bound by the inferred type of c :: Num t => t
        at <interactive>:28:1-38
    • In the expression: otherwise
      In a stmt of a pattern guard for
                     an equation for ‘c’:
        otherwise
      In an equation for ‘c’:
          c | False == True = 0
            | otherwise = 1
Prelude> c | False == True  = 0 |

<interactive>:29:25: error:
    parse error (possibly incorrect indentation or mismatched brackets)

和

Prelude>           c | False == True = 0
Prelude>             | otherwise = 1

<interactive>:31:13: error: parse error on input ‘|’

谢谢。