Isabelle-extreme

Also known as (EXperimental TRansformational Equational Mathematics Engine), this is not a new front-end or library. It is a radically stripped-down meta-logic – the absolute minimal core needed to perform interactive proofs within the Isabelle framework.

| Feature | isabelle-extreme | Isabelle/HOL | |---------|--------------------|---------------| | Logic | Minimal equational logic + fixed point | Higher-order logic | | Types | Simple types (no type classes) | Rich types with type classes | | Recursion | Via fixed point combinator ( fix ) | Primitive recursion, well-founded recursion | | Automation | None (manual rewriting only) | simp , auto , blast , sledgehammer | | Code generation | No | Yes (to ML, Scala, Haskell) | | Library | Empty | Thousands of theorems | isabelle-extreme

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

isabelle extreme This opens a theory file with the extension .ext . Here’s a minimal example: as a and kernel sanity check

No – and that’s the point. isabelle-extreme is intentionally useless for application-scale verification. It lacks data types, recursion schemes, and any form of automation. Trying to prove 1+1=2 requires dozens of manual rewrite steps. However, as a and kernel sanity check , it is invaluable.

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

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