On 06 September 2004 11:11, MR K P SCHUPKE wrote:

Would it cause me any problems if I added "deriving Show" to all the types in compiler/hsSyn? (Can't think of a problem here... is there any reason why this is not done by default? - It is really handy if trying to pattern match on code syntax to be able to see what abstract syntax is generated by certain code)

You'll probably have to derive Show for a *lot* of types, right down to FastString (and in fact deriving Show won't work there, you'll have to write an instance yourself, but it shouldn't be too hard). I guess we don't use Show because it would (a) bloat the compiler a lot, and (b) slow down compiles, and in any case most of the time we want ppr instead. The Show output is going to be pretty hard to read. Cheers, Simon