Why are Partial Functions so prevalent in Prelude?

[atravers]

Why are partial functions so prevalent in Prelude?

The designing of Haskell commenced in 1987, with the first Report being published in 1990 (if you’re interested in learning some more about the origins of Haskell, read A History or Haskell). So Haskell is a language with a 30+ year-old design, and which ought to to explain your (reasonable) list of observations:

• partial functions
• inconsistent documentation
• lack of Maybe producing variants of certain functions
• and incomplete pattern matching
• (…amongst others)

As described here:

m4dc4p:

Here is an example of a silly thing I have to fix - head and tail are deprecated in 9.8 as they are partial (or they give a new warning, at least). One of my dependent libraries (which I don’t control) now fails to compile because it has -Werrors and -Wall enabled. Fortunately I can override cabal options and turn off -Werrors, but that isn’t the point. Code that used to compile now fails to compile.

(emphasis added.)

…merely upgrading GHC alone to or past 9.8 (with the partiality warnings for head and tail) can now cause problems. Trying to apply more recent techniques to older code continues to be a fraught exercise.

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Overall I feel that Haskell is the closest to what I would consider my ideal language. Which is why it both confuses and frustrates me that the language does such a fantastic job of tricking me into believing that it’s safe with it’s beautiful, elegant, sophisticated type system and syntax.

…well done! I don’t think I’ve ever thought about Haskell quite like that before - the only critiques I can think of which are (somewhat) similar were about Haskell’s current I/O model (which is a topic for a separate thread).