过去不常做某事是didn.tusetodosth,还是didn.tusedtodosth说出理由,

Question

过去不常做某事是didn.t use to do sth ,还是didn.t used to do sth 说出理由,

Answer 1

used to 的否定形式在国外语法论坛都是比较有争议的话题
根据字典解释：
A Practical English Grammar, A.J.Thompson and A.V.Martinet:
"didn't use (to)?, did you use (to)?, didn't you use (to)? are fairly common but you must avoid didn't used (to) which is also heard but is considered incorrect.
didn't used to 是错误的.不排除很多外国说英语的当地人会这么用,但只能说非常的informal.
正确的用法是didn't use to do. 但英式英语里会很少这么说,他们会用used not to do这种形式
另外,用never used to do 也是表否定,且没有问题没有争议.
另另外, be used to 是习惯于做某事； used to是过去常常做某事, 意思和用法上截然不同.