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NHEP 5 - Better Default String Type

· 2 min read


By default, Haskell's String type is only an alias for [Char] and as such is inefficient for non-trivial uses (e.g. due to slow appends). The text package provides a more sensible Text type and has become essentially the standard within the Haskell ecosystem.

NeoHaskell should use Text as its default string type under the more familiar name String and support literals via the standard "double quoted" syntax.

Impact on Principle of Least Astonishment

The fact that a simple string literal is inefficient and usually undesirable violates the Principle of Least Astonishment. Most new programmers expect String and "string literals" to work as expected without any additional effort. This change will align NeoHaskell with those expectations.

Impact on Principle of Developer Happiness

As noted below, this change will require less boilerplate of developers and allow them to get to actual code faster. Eliminating the use of OverloadedStrings will also cut down on unexpected type errors.

Impact on Principle of Least Effort

Currently, nearly every Haskell project requires a dependency on text and files are littered with import Data.Texts and {-# LANGUAGE OverloadedStrings #-}s. This change will eliminate all of that overhead and allow the use of a sensible string type with better ergonomics.


In early stages, this can be achieved via prelude and pragmas by newtypeing Text to String and use of OverloadedStrings with:

default IsString String -- where String is the new type over Text


Since Text is the standard for most of the Haskell ecosystem, this change is unlikely to have many negative ramifications, other than possible confusion over the String type in NeoHaskell actually being Text and not String, but this is only of concern for developers stepping outside of the NeoHaskell ecosystem.

Another consideration is the existence of the other common data type ByteString. Text is more often the sensible default for all except extremely performance-critical applications, so this should not be a problem.