An warware: jeri a fihirisa

To, na sami umarnin ku.

Tunda duniyar ci gaban software da shirye-shiryen Haskell na iya zama mai ƙarfi da sarƙaƙiya kamar duniyar salon zamani, bari mu nutse cikin babban maudu'i, jeri a fihirisa. Wannan, gabaɗaya, shine yadda ake dawo da wani takamaiman abu daga jerin Haskell dangane da fihirisar sa. Yana da kwatankwacin ɗaukar ingantattun sutura daga madaidaicin madaidaicin madaidaicin titin jirgin sama. Kamar dai a cikin tufafi, kowane yanki a cikin jerin yana da matsayi na musamman.

Maido da Abubuwan Lissafi ta Fihirisar sa a Haskell

Haskell, kamar sauran yarukan shirye-shirye masu aiki, yana ɗaukar jeri a matsayin jerin abubuwan da aka haɗa inda ko dai jerin fanko ne ko kuma ɓangaren kai da jerin wutsiya. Don samun kashi a takamaiman maƙasudi a cikin Haskell, zaku iya amfani da '!!' ma'aikaci. Ka yi la'akari da wannan a matsayin zaɓin tsayayyen yanki daga tarin catwalk.

let a = [1,2,3,4,5,6]
elementAtIndex = a !! 3

A cikin wannan snippet code, mun ƙirƙiri jeri, 'a', wanda ya ƙunshi abubuwa shida, sannan mu yi amfani da '!!' ma'aikaci don dawo da kashi a fihirisar 3 (tuna, lissafin lissafin Haskell yana farawa daga 0, kamar dai yadda aka yi a farkon 90s na Grunge fashion, akwai wani sauƙi da kai tsaye a ciki).

Fahimtar Ayyukan Shirye-shiryen Bayan Code

Don cikakken fahimtar yadda '!!' ma'aikaci yana aiki, kamar fahimtar yadda wasu haɗe-haɗe na tufafi ke haifar da kaya mai ban sha'awa akan titin jirgin sama. Mai aiki yana bi ta jerin jeri, ya watsar da ɓangaren kai idan fihirisar da ake buƙata ba sifili ba ce kuma yana rage fihirisar da ɗaya, yana mayar da kai lokacin da fihirisar ta buga sifili.

(!!) :: [a] -> Int -> a 
(x:_)  !! 0 = x 
(_:xs) !! n = xs !! (n-1)

Na farko tsari yayi daidai da yanayin lokacin da fihirisar ta zama sifili. Bayan haka, yana dawo da kashi na farko a cikin jeri, mai sauƙi kamar yadda ya dace da ƙaramin rigar baƙar fata tare da kowane kayan haɗi. Na biyu tsari yana maimaituwa kiran aikin akan jelar lissafin kuma yana rage fihirisar. Ta wannan hanyar, yana kama da jera sauran wasan kwaikwayo na kayan kwalliya bayan buɗe abin da aka nuna.

Lissafin Laburaren Fihirisa da Ayyuka

A cikin faffadan sararin shirye-shiryen Haskell, jerin abubuwan da ake iya amfani da su ta hanyar dakunan karatu kamar Bayanai.List wanda ke bada aikin da ake kira GenericIndex. Hakazalika Bayanai.Jeri, wani ɗakin karatu ne wanda ke ba da aiki index, wanda ke aiki daidai kamar haka:

import Data.Sequence
example = fromList [1,2,3,4,5,6]
result = index example 2

Yi la'akari da waɗannan ɗakunan karatu a matsayin mashahuran gidajen kayan gargajiya, koyaushe a shirye suke don ba da rancen fasaha da haɓakar su duk da haka suna gabatar muku da ƙyalli da glitz da kuke so. A taƙaice, kamar yadda salon salo ya ke game da bayyana salon ku na ɗaiɗaiku, shirye-shirye a cikin Haskell yana game da bayyana hanyoyin magance matsaloli cikin ƙayatacciyar hanya da taƙaitacciyar hanya. Ya kasance aiki mai sauƙi kamar samun abubuwan jeri ta fihirisar sa ko ƙirƙirar ƙirƙira ƙira mai ƙima; Haskell ya samu duka, kamar madaidaicin babban titin jirginku

Ka tuna, a ƙarshen rana, mafi kyawun salon a kan titin jirgin sama ko mafi inganci kuma mafi kyawun lamba ba a tsara shi ta hanyar ƙa'idodi ba, amma ta masu hankali masu hankali a bayansa.