Re: [Haskell-cafe] ParallelListComp strange behavior

14 Jan 2015


      If one of the values in the constructor is a constant value, and not in the generator, is it excluded from the zip or is it also zipping that parameter too?


On Jan 13, 2015, at 5:44 PM, Michael Sloan  wrote:
...
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  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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