cppref已经删除std :: is_callable的入口页面,并改用std :: is_invocable条目页面.
但是,std :: is_callable在Visual Studio 2017中仍然可用.
在C 17中使用std :: is_invocable正式表示std :: is_callable [replace | deprecated | removed]
解决方法
是的,is_callable已经被重命名为is_invocable,如
p0604r0所述.本文包括这个决定的理由：
Rename
is_callabletois_invocable:is_callablewould be the most natural name for a trait that answers the question whether a function call expression would be valid or not,which is a strict subset of the expressions,INVOKEsupports,furthermore the changed nameis_invocablemuch clearer expresses its meaning. Releasing the name is_callable allows us in the future to possibly introduce a pureis_callabletrait.
