Haskell类似的类型复制粘贴消除以防万一

Question

case x of 
  Cond expr stmt -> do
        checkExprType expr Bool
        processStmt env stmt
        return env
  AnotherCond expr stmt -> do
        checkExprType expr Bool
        processStmt env stmt
        return env

如何消除此复制粘贴？

Answer 1

你可以制作一个本地定义，它是expr和stmt的函数：

-- I assume this is all inside a 'do' block
let conditionalLike expr stmt = do
        checkExprType expr Bool
        processStmt env stmt
        return env
case x of
    Cond expr stmt -> conditionalLike expr stmt
    AnotherCond expr stmt -> conditionalLike expr stmt