Tackling the awkward squad: monadic input/output, concurrency, exceptions, and foreign-language calls in Haskell

Functional programming may be beautiful, but to write real applications we must grapple with awkward real-world issues: input/output, robustness, concurrency, and interfacing to programs written in other languages. These lecture notes give an overview of the techniques that have been developed by the Haskell community to address these problems. I introduce various proposed extensions to Haskell along the way, and I offer an operational semantics that explains what these extensions mean. This tutorial was given at the Marktoberdorf Summer School 2000. It will appears in the book “Engineering theories of software construction, Marktoberdorf Summer School 2000”, ed CAR Hoare, M Broy, and R Steinbrueggen, NATO ASI Series, IOS Press, 2001, pp47-96. This version has a few errors corrected compared with the published version. Change summary: May 2005: Section 6: correct the way in which the FFI declares an imported function to be pure (no “unsafe ” necessary). Apr 2005: Section 5.2.2: some examples added to clarifyevaluate. March 2002: substantial revision