Presented by Andrew Farmer.

The importance of reasoning about and refactoring programs is a central tenet of functional programming. Yet our compilers and development toolchains only provide rudimentary support for these tasks, leaving the programmer to do them by hand. This talk introduces HERMIT, a toolkit enabling informal but systematic transformation of Haskell programs from inside the Glasgow Haskell Compiler's optimization pipeline. With HERMIT, users can experiment with optimizations and equational reasoning, while the tedious heavy lifting of performing the actual transformations is done for them. The talk will explore design choices in HERMIT, demonstrate its use on examples, and seek input for further development and case studies.