ezyang’s blog

the arc of software bends towards understanding

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October, 2020

The hidden problem(?) with basic block procedures in SSA

Years ago, Nadav Rotem related to me this story about why basic block procedures in Swift are not as good as they seem. Nelson Elhage reminded me about this on Twitter and so I thought this should be put into the public record. Basic block procedures make certain optimizations more difficult. Consider this program: block […]

Idiomatic algebraic data types in Python with dataclasses and Union

One of the features I miss most in non-Haskell programming languages is algebraic data types (ADT). ADTs fulfill a similar role to objects in other languages, but with more restrictions: objects are an open universe, where clients can implement new subclasses that were not known at definition time; ADTs are a closed universe, where the […]