Un esempio grafico delle operazioni di assegnamento di un puntatore la navigazione all’interno di array; essi vanno sotto il nome di aritmetica dei puntatori. Chiedete ad un programmatore C della vecchia guardia come ottimizzare un programma, e la prima cosa che vi dirà sarà di usare l’aritmetica sui puntatori. Capitolo 7 I puntatori in C Introduzione Dichiarazione e inizializzazione dei b[ 3 ] si può accedere effettuando un’operazione aritmetica sull’operatore *(b + 3.

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By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Vediamo un caso concreto: Here is where I learned pointers: You might have a 32 bit platform where the compiler sees ints as 16 or 64 bit wide. Il tutto condito da qualche inevitabile consiglio su come evitare la sindrome da trucco. Now, lets take arrays. It is not a special type, I would say, just a name typedef for the type the compiler spits out.

A null pointer is not guaranteed to actually use the address 0. In tal caso, avendo distrutto p alla riga precedente, ci troviamo con un oggetto inconsistente: This time, p is not a number but an address. But this latter view means that you should really explain STL iterators, and then simply say that pointers are a special case of these.

The article linked to is great, makes sooo much more sense now!

The name of an array is a pointer. In seconda battuta, possiamo usare termini come “meandri”, “nascosti”, o “internals” ed ottenere comunque un buon risultato.


Come potete vedere, il compilatore usa solo aritmetica sui puntatori e pre-incremento. For example, suppose we have an int array called arr.

To begin with, it may not work. Further, you’re not allowed to increment the null pointer, or more generally, a pointer must always point to allocated memory or one element pastor the special null pointer constant 0. Da Wikipedia, l’enciclopedia libera.

C/C++ – Problemi di aritmetica dei puntatori

This means that by adding one to a pointer, we’re moving one byte forward into memory. Capitolo 7 I puntatori in C. Circular definitions Clearer – usually when we talk of the “bit-width” of a platform, we’re referring to the size of an int which is supposed to be the ‘natural’ integer type.

So subtracting pb from pa will yield 1, since they have one element distance.

Instead, describe the problem and what has been done so far to solve it. For a practical example of why not, consider what happens in a segmented memory space.

C/C++ – Problemi di aritmetica dei puntatori –

Does anyone have any good articles or explanations blogs, examples for pointer arithmetic? Stack Overflow works best with JavaScript enabled. Visite Leggi Modifica Modifica wikitesto Cronologia. Jeremy Ruten k 34 Chomel If this question can be reworded to fit the rules in the help centerplease edit the question. The address itself is byte granular, meaning 0x specifies the beginning of memory, and 0x is one byte into memory.

I intended the 4 byte thing to just be an example, but I should probably have made that clearer, because pointers are certainly no guaranteed to be 4 bytes, and they often aren’t. ChomelJoe Mar 21 ’17 at 7: We can also compute ptr – i.


So what we are saying is ‘next address’. If you don’t know what this means, just remember on a bit machine, pointers are 8 bytes, and on a bit machine, pointers are 4 bytes. If you have a null pointer which on most machines corresponds to the address 0and you add the size of an int, you get the address 4. So a more correct way of thinking of it is that pointers are simply iterators allowing you to iterate over allocated memory. Note that incrementing a pointer that contains a null pointer value strictly is undefined behavior.

The example does not show that a pointer is not always incremented by 1 byte, which is often missed. What’s the distance between two pointers pointing to separate segments? So, the key thing to remember is that a pointer is just a word-sized variable that’s typed for dereferencing.

c – Pointer Arithmetic – Stack Overflow

True, that’s an important point. The original value of number is The new value of number is 12 Before main calls cubebyvalue: So if an int is 4 bytes big, pa could contain 0x4 on our platform after having incremented aritmstica 1. Shuffle and deal 2 cards First refinement: Arriviamo quindi al secondo suggerimento: Johannes Schaub – litb k 99