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>> SPEAKER 1: Ejja tagħti ħarsa
fil-librerija CS50,

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speċifikament funzjoni GetInt tagħha.

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Hawnhekk għandna l-għajn prinċipali
kodiċi għall GetInt.

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U tinnota li mhuwiex twil wisq, u
aktar ta 'dan jikkostitwixxi loop filwaqt li -

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loop infinita f'dak - li biss
prospetti valur ladarba aħna ħadthom attwalment

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gotten dak li aħna mistennija.

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Ejja jimxu permezz tiegħu.

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>> Avviż up here ewwel, il-
filwaqt li loop jibda.

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Avviż li jmiss li għandna linja tal-kodiċi
li attwalment jitlob GetString,

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u taħżen l-valur tar-ritorn fil-
varjabbli, imsejħa linja, ta 'spag tip.

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Aħna mbagħad jagħmlu daqsxejn ta 'verifika sanità.

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Jekk null linja ==, allura aħna curiously
ritorn INT_MAX.

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>> Issa jirriżulta li INT_MAX hija
kostanti speċjali ddikjarati mkien ieħor

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li jispeċifika l-akbar possibbli
int li inti tista 'tirrappreżenta b'mod

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programm bħal dan.

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Issa konna arbitrarjament iddeċidiet li jirritornaw
INT_MAX bħala valur sentinella tal

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xorta, waħda li konna riżervati bħala
li jfisser żball kien seħħ.

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Allura l-prezz li nħallsu, naturalment, huwa
li GetInt apparentement ma tistax

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attwalment ritorn numru kbir daqs
INT_MAX, minħabba li, anki jekk trid,

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li l-valur tar-ritorn għandhom verament
jiġi interpretat mill-sejjieħ -

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min bl-użu GetInt -

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bħala żball ta 'xi tip.

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>> Sussegwentement, avviż li stajt iddikjarat
ta 'n int u char c.

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F'dan il-linja li jmiss ta 'kodiċi, I call a
funzjoni msejħa sscanf, li jgħaddi fil-

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erba 'argumenti.

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linja, li hija l-sekwenza tal-utent
ittajpjat fil, "% i% c", li huwa format

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string li jien jistennew l-jista utent
tip, segwit mill-indirizz ta '

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n, u l-indirizz ta 'c.

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Issa sscanf tal skop fil-ħajja huwa tabilħaqq
jiġu skennjati string tfittex għall-

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format partikolari li l-programmer
tkun speċifikata bħala li t-tieni argument.

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F'dan il-każ,% i huwa
hemm, kif inhu% c.

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Mela jekk sscanf jiltaqa 'ma int fil-
input utent, li int ser tkun maħżuna

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ġewwa tal-varjabbli imsejħa n, għaliex
għandna sakemm bħala t-tielet

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argument li sscanf-indirizz ta 'n.

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Li jfisser li sscanf tista 'tabilħaqq jmorru
hemm, u taġġorna l-valur fih.

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>> Issa, fil-każ it-tipi utent
fil xi ħaġa aktar

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minn ċifri wieħed jew aktar -

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fi kliem ieħor, char ta 'xi tip -

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dan it-tieni c varjabbli, li l-indirizz
aħna mgħoddi fis sscanf bħala r-raba tagħha

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argument se jkun popolati wkoll.

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Issa l-rasu ta 'verifika għal
karattru addizzjonali mill-utent huwa

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li jekk hu jew hi ma tikkoperax,
u tipi fil aktar minn sempliċi int,

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aħna ser ikunu jistgħu jiskopriha f'dan
mod, għaliex f'dak il-każ, sscanf

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se jirritorna 2, li jfisser li
iż-żewġ placeholders kienu mimlija

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mal-valuri.

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Iżda aħna qed jittamaw li sscanf minflok
prospetti 1, li tfisser l-utent biss

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pprovdiet int.

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>> Dak li nagħmlu jekk sscanf
tabilħaqq prospetti 1?

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Well, aħna immedjatament ħielsa l-linja li
l-utent ttajpjata, u allura aħna

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immedjatament jirritorna n, li
gotten int.

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Else, jekk sscanf ma ritorn 1, u
l-utent għalhekk ma kkooperax,

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aħna xorta ħielsa l-linja, iżda aħna
issa fil-pront lill-utent biex retry.

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U għaliex aħna qed għadhom ġewwa ta 'dan
loop inkella infinita, il-proċess

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se jerġa 'jibda, u forsi mill-ġdid, u
forsi mill-ġdid, sakemm l-utent fil-fatt

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jipprovdi us int.

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