proof-system

Interactive math proof system

I'm looking for a tool (GUI preferred but CLI would work) that allows me to input math expressions and then perform manipulations of them but restricts me to only mathematically valid operations. Also, the tool must be able to save a session and later prove that the given set of saved operations is valid. Note: I am Not looking for a sy...

Has anybody used a proof assistant to prove soundness of a typed process calculus?

...And have they published the results where I can afford to read them? ...

Help with a Coq proof for SubSequences

Hi, I have the defined inductive types: Inductive InL (A:Type) (y:A) : list A -> Prop := | InHead : forall xs:list A, InL y (cons y xs) | InTail : forall (x:A) (xs:list A), InL y xs -> InL y (cons x xs). Inductive SubSeq (A:Type) : list A -> list A -> Prop := | SubNil : forall l:list A, SubSeq nil l | SubCons1 : forall (x:A) (...