How can I easily write simple tactics at the ML level of Isabelle?

Question

In an Isabelle theory file, I can write simple one-line tactics such as the following:

apply (clarsimp simp: split_def split: prod.splits)

I fi

Answer 1

Additional to the other answers, I think it's worth mentioning that there is a new high-level tactic/proof method construction language (similar to Ltac in Coq) called Eisbach in Isabelle2015, which aims to be easier to understand and maintain.