I’m a bit late but I thought I’d chime in as the Show situation is delicate for me. Pretty much as you said, I’d categorize printing (of general Haskell values) by the audience: Users Programmers Programs Here’s an example of each: "The tar archive is corrupt (truncated)." :: String TruncatedArchive :: FormatError "\1" :: ByteString I would like to add that for the kind targeting programmers, it’s not that I would necessarily like to be able to copy/paste the printing of something into my source code. I use Show for debugging. Rather, I want to know what the value is. So I need the constructor and any fields in it. I think it’s essential for debugging, and I feel spoiled in Haskell that most types have a reasonable Show instance that shows the structure of a value for me. But often, cases like this, it’s just a human-readable string which, as a programmer, is very unhelpful to me. So we already have standard ways of doing each of these, of course: We have things like Doc for pretty printing for users. We have Show for printing the structure of a value. We have binary/cereal/aeson for serializing. The issue is that pretty printing is not very helpful for me. For example, working with the GHC API is particularly difficult because almost all types do not have a Show instance. This breaks my normal Haskell development workflow, which is that I’ll run a function and print out the values. For example, say I’m working with Core and I have an Expr type. I’m pattern matching on the AST constructor by constructor. I generate some core, and I want to see what constructor is used where. If I use the Outputable class to print the Core, all I get is a pretty printed concrete syntax. Pretty, but not useful to me. How can I get that information? So I end up defining a gshow :: Data => a -> Show function, just to see exactly the structure of the data I’m working with, which is what show normally gives me. I think the case of “being able to copy/paste it as source code” is a little bit out of place given things like fromList [(1,'a')] for a Map Int Char and Handle {<1>} (or whatever it was for the Handle type). The Handle’s Show instance is, to my mind, a perfectly legitimate instance for telling you what this value is. It contains an fd and it prints it. It has no Read instance, there’s no pretense of being “serializable” or “copy/pastable”. I have the same issues with exceptions, as noted by Michael. I’d like to know as a programmer what the exception is, as a Haskell value. Separately a way of printing exceptions for users would be welcome too and in the case of web/UI apps it seems very useful.