#10858: Smaller generated instances
-------------------------------------+-------------------------------------
Reporter: nomeata | Owner:
Type: task | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.10.2
Resolution: | Keywords: newcomer
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Revisions:
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Changes (by nomeata):
* keywords: => newcomer
Comment:
Consider this code generated for `Ord` for a product type:
{{{
instance Ord l_acv3 => Ord (ImportDecl l_acv3) where
compare a_acXz b_acXA
= case a_acXz of {
ImportDecl a1_acXB
a2_acXC
a3_acXD
a4_acXE
a5_acXF
a6_acXG
a7_acXH
a8_acXI
-> case b_acXA of {
ImportDecl b1_acXJ
b2_acXK
b3_acXL
b4_acXM
b5_acXN
b6_acXO
b7_acXP
b8_acXQ
-> case (compare a1_acXB b1_acXJ) of {
LT -> LT
EQ
-> case (compare a2_acXC b2_acXK) of {
LT -> LT
EQ
-> case (compare a3_acXD b3_acXL) of {
LT -> LT
EQ
-> case (compare a4_acXE b4_acXM)
of {
LT -> LT
EQ
-> case (compare a5_acXF
b5_acXN) of {
LT -> LT
EQ
-> case (compare
a6_acXG b6_acXO) of {
LT -> LT
EQ
-> case
(compare a7_acXH b7_acXP) of {
LT -> LT
EQ ->
(a8_acXI `compare` b8_acXQ)
GT -> GT
}
GT -> GT }
GT -> GT }
GT -> GT }
GT -> GT }
GT -> GT }
GT -> GT } } }
(<) a_acXR b_acXS
= case a_acXR of {
ImportDecl a1_acXT
a2_acXU
a3_acXV
a4_acXW
a5_acXX
a6_acXY
a7_acXZ
a8_acY0
-> case b_acXS of {
ImportDecl b1_acY1
b2_acY2
b3_acY3
b4_acY4
b5_acY5
b6_acY6
b7_acY7
b8_acY8
-> case (compare a1_acXT b1_acY1) of {
LT -> True
EQ
-> case (compare a2_acXU b2_acY2) of {
LT -> True
EQ
-> case (compare a3_acXV b3_acY3) of {
LT -> True
EQ
-> case (compare a4_acXW b4_acY4)
of {
LT -> True
EQ
-> case (compare a5_acXX
b5_acY5) of {
LT -> True
EQ
-> case (compare
a6_acXY b6_acY6) of {
LT -> True
EQ
-> case
(compare a7_acXZ b7_acY7) of {
LT ->
True
EQ ->
(a8_acY0 < b8_acY8)
GT ->
False }
GT -> False }
GT -> False }
GT -> False }
GT -> False }
GT -> False }
GT -> False } } }
(<=) a_acY9 b_acYa
= case a_acY9 of {
ImportDecl a1_acYb
a2_acYc
a3_acYd
a4_acYe
a5_acYf
a6_acYg
a7_acYh
a8_acYi
-> case b_acYa of {
ImportDecl b1_acYj
b2_acYk
b3_acYl
b4_acYm
b5_acYn
b6_acYo
b7_acYp
b8_acYq
-> case (compare a1_acYb b1_acYj) of {
LT -> True
EQ
-> case (compare a2_acYc b2_acYk) of {
LT -> True
EQ
-> case (compare a3_acYd b3_acYl) of {
LT -> True
EQ
-> case (compare a4_acYe b4_acYm)
of {
LT -> True
EQ
-> case (compare a5_acYf
b5_acYn) of {
LT -> True
EQ
-> case (compare
a6_acYg b6_acYo) of {
LT -> True
EQ
-> case
(compare a7_acYh b7_acYp) of {
LT ->
True
EQ ->
(a8_acYi <= b8_acYq)
GT ->
False }
GT -> False }
GT -> False }
GT -> False }
GT -> False }
GT -> False }
GT -> False } } }
(>=) a_acYr b_acYs
= case a_acYr of {
ImportDecl a1_acYt
a2_acYu
a3_acYv
a4_acYw
a5_acYx
a6_acYy
a7_acYz
a8_acYA
-> case b_acYs of {
ImportDecl b1_acYB
b2_acYC
b3_acYD
b4_acYE
b5_acYF
b6_acYG
b7_acYH
b8_acYI
-> case (compare a1_acYt b1_acYB) of {
LT -> False
EQ
-> case (compare a2_acYu b2_acYC) of {
LT -> False
EQ
-> case (compare a3_acYv b3_acYD) of {
LT -> False
EQ
-> case (compare a4_acYw b4_acYE)
of {
LT -> False
EQ
-> case (compare a5_acYx
b5_acYF) of {
LT -> False
EQ
-> case (compare
a6_acYy b6_acYG) of {
LT -> False
EQ
-> case
(compare a7_acYz b7_acYH) of {
LT ->
False
EQ ->
(a8_acYA >= b8_acYI)
GT ->
True }
GT -> True }
GT -> True }
GT -> True }
GT -> True }
GT -> True }
GT -> True } } }
(>) a_acYJ b_acYK
= case a_acYJ of {
ImportDecl a1_acYL
a2_acYM
a3_acYN
a4_acYO
a5_acYP
a6_acYQ
a7_acYR
a8_acYS
-> case b_acYK of {
ImportDecl b1_acYT
b2_acYU
b3_acYV
b4_acYW
b5_acYX
b6_acYY
b7_acYZ
b8_acZ0
-> case (compare a1_acYL b1_acYT) of {
LT -> False
EQ
-> case (compare a2_acYM b2_acYU) of {
LT -> False
EQ
-> case (compare a3_acYN b3_acYV) of {
LT -> False
EQ
-> case (compare a4_acYO b4_acYW)
of {
LT -> False
EQ
-> case (compare a5_acYP
b5_acYX) of {
LT -> False
EQ
-> case (compare
a6_acYQ b6_acYY) of {
LT -> False
EQ
-> case
(compare a7_acYR b7_acYZ) of {
LT ->
False
EQ ->
(a8_acYS > b8_acZ0)
GT ->
True }
GT -> True }
GT -> True }
GT -> True }
GT -> True }
GT -> True }
GT -> True } } }
}}}
This is huge! And so redundant.
If the implementation of the operators `>` etc. build on the individual
`compare` functions anyways, then it would surely be worth it to use the
`compare` chain that was generated for the `compare` function – i.e.
simply use the default instance.
Also, for the compare function, maybe we should add a function
{{{
thenCmp :: Ordering -> Ordering -> Ordering
thenCmp EQ o2 = o2
thenCmp o1 _ = o1
}}}
to `Data.Ord` and use that to simply this to
{{{
instance Ord l_acv3 => Ord (ImportDecl l_acv3) where
compare a_acXz b_acXA
= case a_acXz of {
ImportDecl a1_acXB
a2_acXC
a3_acXD
a4_acXE
a5_acXF
a6_acXG
a7_acXH
a8_acXI
-> case b_acXA of {
ImportDecl b1_acXJ
b2_acXK
b3_acXL
b4_acXM
b5_acXN
b6_acXO
b7_acXP
b8_acXQ
-> compare a1_acXB b1_acXJ `thenComp`
compare a2_acXC b2_acXK `thenComp`
compare a3_acXD b3_acXL `thenComp`
compare a4_acXE b4_acXM `thenComp`
compare a5_acXF b5_acXN `thenComp`
compare a6_acXG b6_acXO `thenComp`
compare a7_acXH b7_acXP `thenComp`
compare a8_acXI b8_acXQ
}}}
Maybe this is a nice newcomer ticket: Relatively local, rewarding, and
easy to get right.
This is `mkCompareFields` in `TcGenDeriv`
Also look at the other deriving instances for refactoring possibilities!
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10858#comment:1>
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