AS / BUT

AS

In older English as was used as a relative pronoun. The use of as is following:

Such + noun + as: He needs such a boy as will be honest.

The same + noun + as: The book is the same as that.

As + adjective + as (positive): He is as tall as I.

So + adjective + as (negative): She is not beautiful as her sister.

BUT

In older English but was used as a relative pronoun after a negative; it often had the force of a relative pronoun.

There is no but will agree with me.

There is no Hindu but knows the story of Ramayana.

There is no ban but wishes too live.

There is scarcely a child but likes candy.

COMPOUND RELATIVE PRONOUN

Whoever comes is welcome.

Take whichever you like.

I will take with me whomsoever you choose.