my strcpy funcution！
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char *my_strcpy(char *p1, char *p2) { if (p2 == NULL ) return p1; if (p1 == NULL) return 0; else { char *pp1 = p1; char *pp2 = p2; while (p2 != '\0') { *p1++ = *p2++; } *pp1 = '\0'; } return p1; } Is there something wrong in my function and why? Thanks in advantage
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char *my_strcpy(char *p1, char *p2) { if (p2 == NULL ) return p1; if (p1 == NULL) return 0; else { char *pp1 = p1; char *pp2 = p2; while (p2 != '\0') { *p1++ = *p2++; } *pp1 = '\0'; } return p1; } Is there something wrong in my function and why? Thanks in advantage
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char *my_strcpy(char *p1, char *p2) { if (p2 == NULL ) return p1; if (p1 == NULL) return 0; else { char *pp1 = p1; char *pp2 = p2; while (p2 != '\0') { *p1++ = *p2++; } *pp1 = '\0'; } return p1; } Is there something wrong in my function and why? Thanks in advantage
wbgxx wrote:
Is there something wrong in my function
Have you tested it? What makes you think there's something wrong with it?
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wbgxx wrote:
Is there something wrong in my function
Have you tested it? What makes you think there's something wrong with it?
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Pretty much as shown here http://www.space.unibe.ch/comp_doc/c_manual/C/FUNCTIONS/strcpy.html[^]
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wbgxx wrote:
sorry,I can not test it ,can you tell me how to do it ?
Well, how do you intend to become a developper ?? Anyway, you have a couple of choices. - simulate it on paper (run it by hand, line by line with a pencil and some paper). - run it in a debugger (Visual Studio has a good one). Max.
Watched code never compiles.
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char *my_strcpy(char *p1, char *p2) { if (p2 == NULL ) return p1; if (p1 == NULL) return 0; else { char *pp1 = p1; char *pp2 = p2; while (p2 != '\0') { *p1++ = *p2++; } *pp1 = '\0'; } return p1; } Is there something wrong in my function and why? Thanks in advantage
Well try stepping through it with your eyes (aka reading) one line at a time. Then when you get to the line that reads
*p1++ = *p2++;
ask yourself what is the purpose of pointer
pp1. This looks a bit like the sort of confusion that arises from not using useful variable names.It's time for a new signature.
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char *my_strcpy(char *p1, char *p2) { if (p2 == NULL ) return p1; if (p1 == NULL) return 0; else { char *pp1 = p1; char *pp2 = p2; while (p2 != '\0') { *p1++ = *p2++; } *pp1 = '\0'; } return p1; } Is there something wrong in my function and why? Thanks in advantage
The first two
if()tests are not necessary. Also,pp2is not necessary.wbgxx wrote:
while (p2 != '\0')
This will not terminate like you want it to. Richard hints at the last piece of the puzzle.
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