[Haskell-cafe] ParallelListComp strange behavior
Michael Sloan
mgsloan at gmail.com
Wed Jan 14 00:44:58 UTC 2015
In the real code, a number of the lists being zipped have only one
value, such as suPol, sdPol, fault_other, so the result will have at
most one value. Like with zip, the length of the resulting list is
the length of the shortest list. So, [(x,y) | x <- [1] | y <- [1..]]
== [(1,1)]. Maybe you want normal list comprehensions with "," rather
than "|"?
On Tue, Jan 13, 2015 at 3:04 PM, Michael Jones <mike at proclivis.com> wrote:
> I am trying to use ParallelListComp and have code that compiles but only produces one value, but I am not clear why.
>
> The code is something like:
>
> gen :: (a -> b) -> [MyType]
> gen f = [MyType (Just []) (Just c) (Just d) Nothing
> | c <- f
> | d <- [1,2,3,4]
>
> When the gen function is used with take or any other function, only one value is returned.
>
> Is there something here that can’t desugar properly to mzip that will still compile?
>
> Note I did not test this specific code, I am just writing it here to represent the different pieces of a larger piece of real code which is below.
>
> Mike
>
> ———— Real Code ————
>
>
> data Config = Config { onOffControl::Maybe [DEVICE_ON_OFF_CONTROL_BITS]
> , seqUpPos::[Maybe ([DEVICE_SEQ_UP_POSITION_BITS], Word16)]
> , seqDownPos::[Maybe ([DEVICE_SEQ_DOWN_POSITION_BITS], Word16)]
> , tonTimers::[Maybe ([DEVICE_TON_TIMERS_BITS], Word16)]
> , toffTimers::[Maybe ([DEVICE_TOFF_TIMERS_BITS], Word16)]
> , vRange::Maybe [DEVICE_V_RANGE_BITS]
> , vThresh::[Maybe (Word16, Word16)]
> , rstbConfig::Maybe [DEVICE_RSTB_CONFIG_BITS]
> , faultResponse::Maybe [DEVICE_FAULT_RESPONSE_BITS]
> , breakpoint::Maybe ([DEVICE_BREAK_POINT_BITS], Word16)
> , writeProtect::Maybe ([DEVICE_WRITE_PROTECTION_BITS], Word16)
> , specialLot::Maybe Word16
> , deviceId::Maybe Word16
> , statusInfo::Maybe ([DEVICE_STATUS_INFORMATION_BITS])
> , monitorStatus::Maybe ([DEVICE_MONITOR_STATUS_BITS])
> , monitorStatusHistory::Maybe ([DEVICE_MONITOR_STATUS_HISTORY_BITS])
> , monitorBackup::Maybe ([DEVICE_MONITOR_BACKUP_BITS])
> , seqPosCount::Maybe ([DEVICE_SEQ_POSITION_COUNT_BITS], Word16)
>
> generateConfigs seqValues delayValues threshValues = return [Config
> (Just []) -- On off
> ([Just (suPol, suPos),Just (suPol, suPos),Just (suPol, suPos),Just (suPol, suPos),Just (suPol, suPos),Just (suPol, suPos)])
> ([Just (sdPol, sdPos),Just (sdPol, sdPos),Just (sdPol, sdPos),Just (sdPol, sdPos),Just (sdPol, sdPos),Just (sdPol, sdPos)])
> ([Just ([tonMax], tonDelay),Just ([tonMax], tonDelay),Just ([tonMax], tonDelay),Just ([tonMax], tonDelay),Just ([tonMax], tonDelay),Just ([tonMax], tonDelay)])
> ([Just ([toffMax], toffDelay),Just ([toffMax], toffDelay),Just ([toffMax], toffDelay),Just ([toffMax], toffDelay),Just ([toffMax], toffDelay),Just ([toffMax], toffDelay)])
> (Just [rng1, rng2, rng3, rng4, rng5, rng6])
> ([Just (threshOv, threshUv),Just (threshOv, threshUv),Just (threshOv, threshUv),Just (threshOv, threshUv),Just (threshOv, threshUv),Just (threshOv, threshUv)])
> (Just ([rst_en] ++ [rst_time]))
> (Just ([fault_number] ++ [fault_action] ++ [fault_delay] ++ fault_other ++ [fault_count]))
> (Just ([], 0))
> (Just ([], 0))
> (Just 0)
> Nothing
> Nothing
> Nothing
> Nothing
> Nothing
> Nothing
> | suPol <- [DEVICE_seq_up_position_bits]
> | suPos <- seqValues
> | sdPol <- [DEVICE_seq_down_position_bits]
> | sdPos <- seqValues
> | tonMax <- DEVICE_ton_timers_bits
> | tonDelay <- delayValues
> | toffMax <- DEVICE_toff_timers_bits
> | toffDelay <- delayValues
> | rng1 <- DEVICE_v_range_bits1
> | rng2 <- DEVICE_v_range_bits2
> | rng3 <- DEVICE_v_range_bits3
> | rng4 <- DEVICE_v_range_bits4
> | rng5 <- DEVICE_v_range_bits5
> | rng6 <- DEVICE_v_range_bits6
> | threshOv <- threshValues
> | threshUv <- threshValues
> | rst_time <- DEVICE_rstb_config_bits_time
> | rst_en <- DEVICE_rstb_config_bits_en
> | fault_number <- DEVICE_fault_response_bits_retry_number
> | fault_other <- [DEVICE_fault_response_bits_other]
> | fault_count <- DEVICE_fault_response_bits_count
> | fault_delay <- DEVICE_fault_response_bits_delay
> | fault_action <- DEVICE_fault_response_bits_action
> ]
>
> generateSeqValues :: IO [Word16]
> generateSeqValues = do
> vs <- replicateM 10 (randomRIO (0x0000, 0x03FF))
> return vs
>
> generateDelayValues :: IO [Word16]
> generateDelayValues = do
> vs <- replicateM 10 (randomRIO (0x0000, 0x1FFF))
> return vs
>
>
> generateThreshValues :: IO [Word16]
> generateThreshValues = do
> vs <- replicateM 10 (randomRIO (0x0000, 0x00FF))
> return vs
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