# Difference between revisions of "List of partial functions"

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==Partial functions in Prelude== |
==Partial functions in Prelude== |
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− | ===List functions=== |
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+ | ===Functions that aren't even partial=== |
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− | * maximum |
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+ | {| class="wikitable" |
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− | * minimum |
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+ | ! Function |
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− | * head |
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+ | ! Witness |
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− | * tail |
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+ | |- |
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− | * init |
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+ | | error |
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− | * last |
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+ | | error "x" |
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− | * foldl |
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+ | |- |
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− | * foldl' |
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+ | | undefined |
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− | * foldl1 |
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+ | | undefined |
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− | * foldl1' |
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+ | |} |
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− | * foldr1 |
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− | * cycle |
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− | * !! |
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− | * genericIndex |
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− | * length |
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− | * sum |
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− | * reverse |
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− | * ... (todo) |
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− | === |
+ | ===List functions=== |

− | * fromJust |
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+ | {| class="wikitable" |
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+ | ! Function |
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+ | ! Only partial for infinite lists |
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+ | ! Witness |
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+ | |- |
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+ | | maximum |
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+ | | No |
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+ | | maximum [] |
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+ | |- |
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+ | | minimum |
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+ | | No |
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+ | | minimum [] |
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+ | |- |
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+ | | head |
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+ | | No |
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+ | | head [] |
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+ | |- |
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+ | | tail |
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+ | | No |
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+ | | tail [] |
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+ | |- |
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+ | | init |
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+ | | No |
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+ | | init [] |
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+ | |- |
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+ | | last |
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+ | | No |
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+ | | last [] |
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+ | |- |
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+ | | foldl |
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+ | | Yes |
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+ | | foldl (const (const ())) () [0..] |
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+ | |- |
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+ | | foldl' |
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+ | | Yes |
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+ | | foldl' (const (const ())) () [0..] |
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+ | |- |
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+ | | foldl1 |
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+ | | No |
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+ | | foldl1 (const (const ())) [] |
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+ | |- |
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+ | | foldl1' |
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+ | | No |
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+ | | foldl1' (const (const ())) [] |
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+ | |- |
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+ | | foldr1 |
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+ | | No |
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+ | | foldr1 (const (const ())) [] |
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+ | |- |
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+ | | cycle |
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+ | | No |
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+ | | cycle [] |
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+ | |- |
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+ | | !! |
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+ | | No |
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+ | | [] !! 0 |
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+ | |- |
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+ | | filter |
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+ | | Yes |
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+ | | filter (const False) [0..] |
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+ | |- |
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+ | | dropWhile |
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+ | | Yes |
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+ | | dropWhile (const True) [0..] |
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+ | |- |
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+ | | length |
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+ | | Yes |
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+ | | length [0..] |
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+ | |- |
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+ | | sum |
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+ | | Yes |
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+ | | sum [0..] |
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+ | |- |
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+ | | product |
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+ | | Yes |
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+ | | product [0..] |
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+ | |- |
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+ | | reverse |
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+ | | Yes |
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+ | | reverse [0..] |
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+ | |} |
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===Other=== |
===Other=== |
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− | * read |
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+ | {| class="wikitable" |
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− | * quot |
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+ | ! Function |
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− | * rem |
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+ | ! Witness |
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− | * quotRem |
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+ | |- |
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− | * div |
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+ | | read |
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− | * mod |
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+ | | read "x" :: Int |
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− | * divMod |
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+ | |- |
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− | * ... (todo) |
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+ | | quot |
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+ | | 1 `quot` 0 |
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+ | |- |
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+ | | rem |
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+ | | 1 `rem` 0 |
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+ | |- |
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+ | | quotRem |
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+ | | 1 `quotRem` 0 |
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+ | |- |
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+ | | div |
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+ | | 1 `div` 0 |
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+ | |- |
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+ | | mod |
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+ | | 1 `mod` 0 |
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+ | |- |
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+ | | divMod |
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+ | | 1 `divMod` 0 |
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+ | |- |
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+ | | succ |
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+ | | succ () |
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+ | |- |
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+ | | pred |
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+ | | pred () |
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+ | |- |
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+ | | toEnum |
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+ | | toEnum 1 :: () |
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+ | |- |
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+ | | (^) |
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+ | | 1 ^ (-1) |
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+ | |- |
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+ | | fail |
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+ | | fail "x" :: Either () () |
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+ | |- |
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+ | |colspan="2" | ... (todo) |
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+ | |} |
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==Partial functions in other base libraries== |
==Partial functions in other base libraries== |
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− | ... (todo) |
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+ | ===Data.List=== |
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+ | |||

+ | {| class="wikitable" |
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+ | ! Function |
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+ | ! Only partial for infinite lists |
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+ | ! Witness |
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+ | |- |
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+ | | genericIndex |
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+ | | No |
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+ | | genericIndex [] 0 |
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+ | |- |
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+ | | genericLength |
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+ | | Yes |
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+ | | genericLength [0..] :: Integer |
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+ | |} |
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+ | |||

+ | ===Data.Map=== |
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+ | |||

+ | {| class="wikitable" |
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+ | ! Function |
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+ | ! Witness |
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+ | |- |
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+ | | (!) |
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+ | | Map.empty ! () |
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+ | |} |
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+ | |||

+ | ===Data.Maybe=== |
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+ | |||

+ | {| class="wikitable" |
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+ | ! Function |
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+ | ! Witness |
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+ | |- |
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+ | | fromJust |
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+ | | fromJust Nothing |
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+ | |} |
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==Partial functions in other Haskell Platform packages== |
==Partial functions in other Haskell Platform packages== |
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− | ... (todo) |
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+ | {| class="wikitable" |
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+ | ! Function |
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+ | ! Witness |
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+ | |- |
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+ | |colspan="2" | ... (todo) |
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+ | |} |
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+ | |||

+ | [[Category:Pages under construction]] |

## Latest revision as of 04:31, 26 April 2021

## Contents

## Partial functions in Prelude

### Functions that aren't even partial

Function | Witness |
---|---|

error | error "x" |

undefined | undefined |

### List functions

Function | Only partial for infinite lists | Witness |
---|---|---|

maximum | No | maximum [] |

minimum | No | minimum [] |

head | No | head [] |

tail | No | tail [] |

init | No | init [] |

last | No | last [] |

foldl | Yes | foldl (const (const ())) () [0..] |

foldl' | Yes | foldl' (const (const ())) () [0..] |

foldl1 | No | foldl1 (const (const ())) [] |

foldl1' | No | foldl1' (const (const ())) [] |

foldr1 | No | foldr1 (const (const ())) [] |

cycle | No | cycle [] |

!! | No | [] !! 0 |

filter | Yes | filter (const False) [0..] |

dropWhile | Yes | dropWhile (const True) [0..] |

length | Yes | length [0..] |

sum | Yes | sum [0..] |

product | Yes | product [0..] |

reverse | Yes | reverse [0..] |

### Other

Function | Witness |
---|---|

read | read "x" :: Int |

quot | 1 `quot` 0 |

rem | 1 `rem` 0 |

quotRem | 1 `quotRem` 0 |

div | 1 `div` 0 |

mod | 1 `mod` 0 |

divMod | 1 `divMod` 0 |

succ | succ () |

pred | pred () |

toEnum | toEnum 1 :: () |

(^) | 1 ^ (-1) |

fail | fail "x" :: Either () () |

... (todo) |

## Partial functions in other base libraries

### Data.List

Function | Only partial for infinite lists | Witness |
---|---|---|

genericIndex | No | genericIndex [] 0 |

genericLength | Yes | genericLength [0..] :: Integer |

### Data.Map

Function | Witness |
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(!) | Map.empty ! () |

### Data.Maybe

Function | Witness |
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fromJust | fromJust Nothing |

## Partial functions in other Haskell Platform packages

Function | Witness |
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... (todo) |