On 21 December 2012 11:16, Joachim Breitner
Prelude> :script /home/jojo/.cabal/share/ghc-heap-view-0.4.0.0/ghci Prelude> let x = [1..10] Prelude> x [1,2,3,4,5,6,7,8,9,10] Prelude> :printHeap x _bh [S# 1,S# 2,S# 3,S# 4,S# 5,S# 6,S# 7,S# 8,S# 9,S# 10]
Note that the tools shows us that the list is a list of S# constructors, and also that it is still hidden behind a blackhole. After running System.Mem.performGC, this would disappear.
Why do you call it a "blackhole"? I assume you mean a thunk that has been evaluated and updated with its value. The commonly used term for this is "indirection". A blackhole is used to detect when a thunk's value depends on itself (e.g., in "let x = id x in ..." the thunk for x may get turned into a black hole). It's a minor thing, but I think it's a good idea to stick to existing terminology. Otherwise, it looks like a useful tool. Eventually, we probably want an interactive graph where we can click a node to evaluate it (or to show/hide children nodes). -- Push the envelope. Watch it bend.