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The unofficial motto of Haskell, the predominant lazy functional language, has long been:

“Avoid success at all costs.”

This is attributed to Simon L. Peyton-Jones (SPJ), the main architect of the Haskell language and the GHC compiler, and mentioned in the slides of a talk he gave at the POPL conference in 2003.

This seems an odd statement. What’s wrong with a bit of success?

The exact meaning of this statement is controversial. Simon Marlow, another major Haskell figure, quotes SPJ that this statement (expression?) should not be bracketed (avoid success) at all costs, i.e. …


If you try to research this question, you might come up with confusing and contradictory answers, strongly-stated opinions, and loads of technical jargon.

The answer depends which perspective the questioner is coming from, and what assumptions, expectations and preconceived notions they bring with them.

Correctly written Haskell is fast for a high-level language

Haskell is a high-level language — a tool used to write programs with a goal of avoiding the programmer having to specify implementation details, as far as practical. This is typically the most productive way of writing most software, where performance must be ‘adequate’ rather than optimum.

In this space, developers typically reach for dynamically typed…

Ari Fordsham

A developer interested in Haskell and functional programming

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