(* Prove a simple property manually – no automation! ) lemma add_zero: "add 0 m = m" unfolding add_def by (rule fix_eq) ( primitive rule only *)

Most people in the formal verification community are familiar with – the powerful, mainstream interactive theorem prover used for everything from operating system kernels (seL4) to financial protocols. But lurking in the source tree and early development history is a hidden gem: isabelle-extreme .

Beyond the Mainland: Exploring isabelle-extreme , the Minimalist Core of Interactive Theorem Proving

theory Scratch imports Main begin (* Define addition via fixed point *) definition add :: "nat ⇒ nat ⇒ nat" where "add ≡ fix (λadd n m. if n = 0 then m else add (n-1) (m+1))"

If you have Isabelle installed (2023 or later), you can launch isabelle-extreme directly from the command line:

Notice: no simp , no induct . Every proof step must explicitly invoke a primitive inference rule.

Have you experimented with minimal logics inside Isabelle? Share your experiences below!

Isabelle-extreme

(* Prove a simple property manually – no automation! ) lemma add_zero: "add 0 m = m" unfolding add_def by (rule fix_eq) ( primitive rule only *)

Most people in the formal verification community are familiar with – the powerful, mainstream interactive theorem prover used for everything from operating system kernels (seL4) to financial protocols. But lurking in the source tree and early development history is a hidden gem: isabelle-extreme . isabelle-extreme

Beyond the Mainland: Exploring isabelle-extreme , the Minimalist Core of Interactive Theorem Proving (* Prove a simple property manually – no automation

theory Scratch imports Main begin (* Define addition via fixed point *) definition add :: "nat ⇒ nat ⇒ nat" where "add ≡ fix (λadd n m. if n = 0 then m else add (n-1) (m+1))" Have you experimented with minimal logics inside Isabelle

If you have Isabelle installed (2023 or later), you can launch isabelle-extreme directly from the command line:

Notice: no simp , no induct . Every proof step must explicitly invoke a primitive inference rule.

Have you experimented with minimal logics inside Isabelle? Share your experiences below!