Great stuff Don,
I've learned from experience that in 2 yrs time I will have forgotten why that
INLINE is there, and may remove it. (Probably not in this particular case, but
something similar.) You may think that the info is in the commit message, but
in practice I just don't do a darcs annotate to see which patches modified the
line, and look at the commit log.
I think it's better to invest effort in putting documentation in the source
code. Rather than clutter up the (Bits Int) instance, nowadays I add
-- See Note [Constant folding for rotate]
and put a block comment, headed by that same string, lower down in the file.
I have found that this is a robust and effective way of documenting things.
Does that make sense?
I've pushed a patch doing this to Data.Bits.
Maybe I should update the programming conventions wiki!
Simon
| -----Original Message-----
| From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Don
| Stewart
| Sent: 02 May 2008 00:10
| To: [email protected]
| Subject: patch applied (packages/base): Inline [EMAIL PROTECTED], enables
rotate to be constant
| folded
|
| Thu May 1 16:01:52 PDT 2008 Don Stewart <[EMAIL PROTECTED]>
| * Inline [EMAIL PROTECTED], enables rotate to be constant folded
|
| All other Bits instances seem to inline well enough on their own
| to enable constant folding, e.g.
|
| sumU . mapU (`shift` 3) . replicateU 10000000 $ (7 :: Int)
|
| goes to:
|
| Main.$wfold =
| \ (ww_sOb :: Int#) (ww1_sOf :: Int#) ->
| case ww1_sOf of wild_XM {
| __DEFAULT -> Main.$wfold (+# ww_sOb 56) (+# wild_XM 1);
| 10000000 -> ww_sOb
| }
|
| With this patch, rotate gets inlined and folded too,
|
| sumU . mapU (`rotate` 3) . replicateU 10000000 $ (7 :: Int)
|
| to:
|
| Main.$wfold =
| \ (ww_sO7 :: Int#) (ww1_sOb :: Int#) ->
| case ww1_sOb of wild_XM {
| __DEFAULT -> Main.$wfold (+# ww_sO7 56) (+# wild_XM 1);
| 10000000 -> ww_sO7
|
| Whereas it was left as a call to $wrotate before.
|
|
|
| M ./Data/Bits.hs -1 +8
|
| View patch online:
| http://darcs.haskell.org/packages/base/_darcs/patches/20080501230152-cba2c-
| adb8ea1981dbc6427b2d85b054533517ffc3b4c3.gz
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