I-Turbo Pascal. Ngenkathi ... ingabe i-loop ene-precondition

I-Turbo Pascal, nakuba kungenjalo uhlelo lokusebenza oluthandayo lwezinhlelo zomhlaba jikelele, kodwa abadali abenza izinyathelo zokuqala kwisofthiwe yokubhala, baqale ukujwayela nale ndawo. Inikeza umbono wokuhlanganisa, opharetha, imisebenzi kanye nezinqubo, kanye nezinye izinto eziningi. Isibonelo, ngenkathi ufunda, umqambi uzohlangana nemijikelezo eTurbo Pascal: Ngesikhathi, Ngokuba, Futhi Phinda.

Umqondo womjikelezo nokuhluka kwawo

Umjikelezo ubizwa ngokuthi izenzo eziphindaphindiwe. Kule ndawo, sisebenzisa:

• With parameter (For ... kuya ^ do);
• With precondition (Ngenkathi ... yenza);
• Nge-postcondition (Phinda ... kuze kube).

Uhlobo lokuqala lusetshenziswe uma lwaziwa kusengaphambili ukuthi zingaki izinyathelo ekusombulweni kwenkinga. Kodwa-ke, kunemisebenzi eminingi uma kungekho ulwazi mayelana nokuthi kaningi kwesinye noma esinye isenzo sizophindaphindiwe. Kulokhu, ku-Pascal Nakuba umjikelezo uba usizo, njengokuthi, ngokuphindaphindiwe, bese uphinda.

Isakhiwo somjikelezo

Iyini isisekelo somsebenzi ePascal Ngenkathi, Ukuphindaphinda nokuphindaphinda imijikelezo? Lezi zakhiwo zinesihloko nomzimba. Isigaba sokuqala sichaza iziguquguquki ezizosebenza ", izimo zokuqinisekisa iqiniso, isikhathi lapho umzimba uzokwenziwa khona zichazwe. Esigabeni sesibili, izinkulumo zilotshiwe okufanele zisetshenziswe uma isimo sinelisekile, okungukuthi, iQiniso, futhi akulona Amanga.

Uma ukulinganisa kwenziwa ekwenzeni ikhodi yokugcina, bese ubuyela ekhanda lapho isimo sihlolwe khona. Eqinisweni, imisebenzi iphindaphindwa, kanti uma kungenakwenzeka kwalesi simo, lolu hlelo "luyayeka" umjikelezo futhi lwenze imisebenzi eqhubekayo.

I-loop ngenkathi ibukeka kanje. I-Pascal ABC nezinhlelo ezifanayo zidinga ukubhala le khodi:

• Ngenkathi isimo senza;
• Qala;
• Umzimba womjikelezo;
• Qeda.

Uma kwenzeka ukuthi u-opharetha oyedwa (1 isenzo) ekhishwa emzimbeni we-loop, "ukuqala" amabakaki angaqedwa.

I-flowchart yomjikelezo

E-Turbo Pascal Ngenkathi enezici ezilandelayo:

• Izimo ezinzima zingasetshenziswa ngaphakathi kwesakhiwo;
• Ngemuva kwezwi, akufanele kube khona i-semicolon (lokhu kubhekwa njengephutha eTurbo Pascal nasePascal ABC);
• Okuguquguqukayo, okuqhubekayo noma okukhulunywayo okusetshenziselwa lapho kutholakala ukukhishwa okungamanga kwe-subroutine kumele kube nohlobo olunengqondo, okungukuthi, i-Boolean.

Umdwebo we-block wale nguqulo womjikelezo ubheka okulandelayo. Ibonisa ukulandelana kwezenzo.

I-algorithm yomjikelezo

Ezindaweni ezilula zokuhlela, kufaka phakathi iPascal ABC, Nakuba loop isebenza ngokuvumelana nalesi simiso esilandelayo:

• Ukubuyekeza okunikeziwe, okusho, ukuphindaphinda, kuzodlulela kaningi kuze kube yilapho isimo siyiqiniso (Eqinisweni);
• Uma nje isimo singenelisekile futhi sinikeza impendulo yamanga (noma "kungamanga"), isitatimende sishiya loop;
• Ngokushesha lokhu kwenzeka, uhlelo "lwaya" ekwakheni, ngemuva komjikelezo.

Lena umehluko obalulekile kusukela ngesikhathi sokuphinda, okuwukuthi, umjikelezo kanye nesimo esinqunyiwe kusuka ekuthumeni okulandelayo.

Kubaluleke kakhulu ukuhlinzeka emzimbeni we-loop ukuguqulwa kokugcina kuyahlukahluka okucacisiwe ku-While ngenkathi uhamba. Kunoma yikuphi, kufanele ngelinye ilanga kufanele kube nesimo esinikeza inani elingamanga. Uma kungenjalo, i-loop izokwenzeka, bese kuzomele usebenzise izinyathelo ezengeziwe zokuphuma ku-compiler. Amaphutha anjalo abhekwa njengesihluku futhi angenakuthethelelwa.

Ngikhipha kanjani lolu hlelo ngenkathi ngisondeza?

Ngokuvamile isimo senzeke ngenkathi umqhubi we-Pascal ngenkathi ephawula i-loop kukhodi ebhaliwe. Kusho ukuthini lokhu? Ukuguqulwa kuphindwe inombolo engapheli yezikhathi, ngoba isimo sihlale siqotho. Isibonelo, nasi isigaba sehlelo:

• Ngenkathi 2> 1 yenza;
• Bhala (1).

Kulokhu, ukuyeka umsebenzi, cindezela CTRL + F2.

Kunezindlela ezimbili zokulawula lokhu kuziphatha kohlelo. Isibonelo, uma ufaka ikhodi Qhubeka, okuzodlulisa ukulawula ekuqaleni kokukhishwa kwe-cyclic (lapha isimo sokuphuma esikhwameni silawulwa, okungukuthi ukukhishwa kwe-current iteration kuzophazanyiswa). Khona-ke ukulawula kudluliselwa ku-Loop ngenkathi isheke langaphambilini.

Isitatimende se-Break sikwazi ukukhipha ukukhishwa kwe-loop yonke nokulawula ukudlulisa ku-iteration elandelayo. Lapha, ukukhishwa kwesakhiwo ngeke kulawulwe. Isithombe sibonisa izibonelo zokusebenzisa la ma-opharetha.

Ukuxazulula Inkinga

Cabanga Ngenkathi i-loop. Umsebenzi kaPascal ukuxazulula izinhlobonhlobo. Ake sihlale isikhathi esilula ukuqonda isimiso somsebenzi. Ukuxazulula imisebenzi ohlelweni lwePascal ABC. Kodwa izithombe ze-classical Turbo Pascal imvelo zizovela ukuze ziqhathaniswe.

Umsebenzi 1: Unikezwe umsebenzi Y = 5-X ^ 2/2. Dala itafula lamagugu ngesinyathelo sh = 0.5 ngesikhathi sokuphumula [-5; 5].

I-Algorithm yezenzo:

• Setha inani lokuqala lokuhluka X elilingana no -5 (okungukuthi, ukuqala kwesikhathi);
• Bala inani le-Y kuze kube yilapho ukuguquguquka x kufinyelela ekupheleni kwesigaba esicacisiwe;
• Bonisa izindinganiso zomsebenzi kanye ne-abscissa (X);
• Yandisa i-X ngesinyathelo esinikeziwe.

Leli ikhodi ohlelweni lwe-Pascal ABC.

Ikhodi ibukeka kanjani e-Turbo Pascal. Isithombe ngezansi sibonisa lokhu ngokucacile.

Umsebenti wesi-2: Wanikezela luhlaka A, luhlanganisa tinombolo letinhle netinombolo letibi. Iqukethe izakhi ezingu-10. Kudingekile ukwakha i-matrix B, lapho izakhi ezihle ze-A ezilandelanayo zizoboniswa. Bonisa esikrinini isibalo sezikwele ngenani le-matrix entsha.

I-Algorithm yezenzo:

• Kubalulekile ukubhala i-subroutine ezo "sebenza" kuphela ngezici ze-A eziba nenkomba. Ku-loop, ukubaluleka kokuguquguquka okunomthwalo wobuningi benkomba kuzokwandiswa ngo-2.
• Uma inombolo ene-index evela ku-matrix A ihambelana nesimo x> 0, bese kuqhathaniswa ne-counter of the array elements. 1. Inani lamanje le-variable variable liyoba inkomba yenombolo ekopishiwe ku-B.
• Okokuqala, isiqubulo, esinomthwalo wokuthola isibalo sezikwele zezinombolo ezinhle, sinikezwe u-0. Khona-ke, lo msebenzi uzokwenziwa: inani elisha lesikwele lengezwe kwisamba sangaphambilini.
• Ungesabi uma kungezona zonke izinombolo ezinhle eziye zisuka komunye umthamo kuya kwesinye. Kufanele uqaphele. Abaningi bezinhlelo ze-novice babhala kabusha ikhodi ngesaba. Kumele sifunde ngokucophelela isimo: izinombolo ezinhle ezisezindaweni ngisho "nezindawo", okungukuthi, ezinezinhlamvu eziphindaphindiwe ze-2.

Ukulandela imiyalelo kuyadingeka ukuqinisekisa ukuthi izibalo zilungile. Ngesinye isikhathi ngosizo lendlela ungathola amaphutha angaboni emehlweni akho uma uvame ukuhlola ikhodi ebhaliwe.

Uma wenza izibalo zomqulu, ungaqiniseka ukuthi uhlelo lusebenza kahle. Lokhu, futhi, kubonisa ukuthi i-algorithm yokudala ikhodi ilungile, ukulandelana kwezinyathelo kuholela ekupheleni kokuqondakalayo.