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[Powered by Google Translate] CHRIS GERBER: kazi ni mfululizo wa hatua ndani ya

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kubwa mpango, ambayo ni kawaida lengo kuitwa

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mara nyingi na kutoka nyingi maeneo mengine katika

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mpango.

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Wakati kujenga kazi C, moja ya mahitaji ni kwa

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bayana thamani kurudi aina.

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kesi ya rahisi ni hali ambapo wito

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code ni si na wasiwasi na matokeo ya kazi.

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Hii inaweza kuwa kesi wakati sisi ni kuchapisha data kwa

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kuonyesha ya mtumiaji, kama kwa printf.

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Katika kesi hiyo, tunaweza kutangaza thamani ya kurudi

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kuwa ya utupu aina.

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Kutumia utupu tu anamwambia compiler kwamba hakuna

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thamani watarejeshwa.

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Hebu kuona nini hii inaonekana kama.

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>> Hebu kusema kwamba tuna kazi kuitwa say_hello kwamba

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inachukua moja hoja.

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Tutaweza kupita jina la mtu na itakuwa kuonyesha salamu

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kwenye screen.

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jina itakuwa ya * aina Char.

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Na tutaweza bayana kwamba kama hoja.

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Maombi yangu haina haja ya kujua nini ilichapishwa au kama ni

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kilichapishwa.

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Hivyo thamani kurudi itakuwa ya utupu aina.

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Kazi hii inaweza magazeti kwa screen na amri kama

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printf ("Hello,% s \ n

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", Jina);.

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salamu yataoneshwa na kudhibiti itakuwa kupita

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nyuma kwa kificho wito.

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Jambo moja kukumbuka ni kwamba wakati thamani kurudi aina ni batili,

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huna haja kwa pamoja kurudi

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taarifa katika kazi.

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Kama wewe kuchagua ni pamoja na moja, si ni pamoja na thamani ya kurudi

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kama hoja.

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>> Katika baadhi ya matukio, ni mantiki ya kurudi

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thamani kutoka kazi.

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Hebu kusema kwamba tulikuwa kuandika kazi kuitwa add_floats.

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Tutaweza kupita hoja mbili, ikifungwa,

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kuitwa kwanza na pili.

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Na itakuwa kutuambia nini Jumla ya ikifungwa wale ni.

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Tunajua kwamba kama sisi kuongeza ikifungwa mbili pamoja, matokeo

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itakuwa kuelea.

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Kutokana na kwamba, sisi kuchagua aina ya kurudi kwa kuelea.

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Kazi hii utakaotenda hayo mahesabu na kurudi

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maadili katika taarifa kama kurudi

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kwanza + pili;.

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Wakati udhibiti ni kupita nyuma code wito,

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kusababisha thamani sasa inapatikana kwa kificho kwamba.

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Tunaweza kuhifadhi thamani hii kama hivyo: kuelea matokeo =

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add_floats (3.14, 1.62

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);.

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Matokeo katika kesi hii ingekuwa sasa vyenye thamani 4.76.

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>> Kama ukumbusho, floating kumweka maadili ni imprecise.

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Hivyo kama hii ilikuwa hesabu za fedha, kwa kutumia dola na

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senti, sisi inaweza kufikiria data sahihi ya aina kama vile

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int na kufanya hesabu katika pennies.

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>> Kesi nyingine ambapo sisi wanataka kurudi thamani kutoka

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kazi ni wakati tunataka kujua kama kazi ilikuwa

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mafanikio.

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Kama haikuwa na mafanikio, sisi pia nataka kujua ni aina gani ya

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Hitilafu ilitokea.

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Hebu kusema kwamba sisi ni kujaribu kufungua faili kwenye disk ya kuhesabu

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idadi ya herufi katika hilo.

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Kama faili hawezi kufunguliwa, tunataka kuwa na uwezo wa kuacha na

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kuwaambia mtumiaji juu ya tatizo.

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>> Tutamwita kazi count_file_chars yetu na mapenzi

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kuchukua moja hoja.

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Sisi itabidi kupita katika jina la faili kwa kutumia

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Char * kuitwa filename.

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Kazi hii ili kuangalia kitu kama hiki.

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Katika mfano huu, tulitazama kuhesabu akarudi

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kuwa 0 au zaidi.

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Hii inatuacha integers hasi kwa

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kutumia kama maadili sentinel.

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thamani sentinel ni tu thamani maalum ambayo si

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data halali lakini haina kuwasilisha taarifa.

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Hapa, kama mimi kurudi -1 kwa kificho wito, mimi ni

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kweli kutuma ujumbe kwamba kosa ilitokea wakati

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kujaribu kupata faili.

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Mimi nilikuwa basi kuangalia kwamba thamani ya kurudi ili kuamua kama yangu

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kazi wito ilikuwa na mafanikio.

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Kama idadi ilikuwa 0 au zaidi, napenda kujua

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idadi ya herufi katika faili.

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Kama, hata hivyo, idadi ilikuwa chini ya 0, mimi nilikuwa tu

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magazeti kwamba tatizo ilitokea.

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Moja biashara-off ya kuzingatia ni kwamba kwa reservera wote

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maadili hasi kama maadili sentinel, kuchukua hii ni

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32-bit integer, mimi kimsingi kuchukuliwa mbali duniani

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Bilioni 2 inawezekana kurudi maadili.

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>> Kurudi thamani aina ni moja ya mambo muhimu zaidi ya

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kazi wito.

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Hopefully hii overview mfupi imesaidia unafikiri juu ya

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tatu muhimu aina: batili, maadili matokeo, na maadili sentinel,

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na wakati kila mmoja wa tatu inaweza kuwa

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sahihi katika code yako.

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Shukrani kwa ajili ya kuangalia.