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What's the difference between (size_t)-1 and ~0?
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What's the difference between (size_t)-1 and ~0?
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I've seen both (size_t)-1 and ~0 used to represent large numbers, or numbers with all their bits flipped.
Is there any difference between the two? If so, what is it?
I found this question: What is the difference between -1 and ~0, however it did not answer my question because I'm dealing with unsigned integers (such as size_t), as opposed to signed integers (such as int).
c unsigned ones-complement
asked 1 hour ago
JL2210JL2210
623121
add a comment |
I've seen both (size_t)-1 and ~0 used to represent large numbers, or numbers with all their bits flipped.
Is there any difference between the two? If so, what is it?
I found this question: What is the difference between -1 and ~0, however it did not answer my question because I'm dealing with unsigned integers (such as size_t), as opposed to signed integers (such as int).
c unsigned ones-complement
asked 1 hour ago
JL2210JL2210
623121
Note that~0is a signed quantity — you'd need~0Uto make it unsigned.
– Jonathan Leffler
1 hour ago
Should I edit that?
– JL2210
1 hour ago
3
Since you've got some answers which addresses~0rather than~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.
– Jonathan Leffler
1 hour ago
add a comment |
I've seen both (size_t)-1 and ~0 used to represent large numbers, or numbers with all their bits flipped.
Is there any difference between the two? If so, what is it?
I found this question: What is the difference between -1 and ~0, however it did not answer my question because I'm dealing with unsigned integers (such as size_t), as opposed to signed integers (such as int).
c unsigned ones-complement
asked 1 hour ago
JL2210JL2210
623121
I've seen both (size_t)-1 and ~0 used to represent large numbers, or numbers with all their bits flipped.
Is there any difference between the two? If so, what is it?
I found this question: What is the difference between -1 and ~0, however it did not answer my question because I'm dealing with unsigned integers (such as size_t), as opposed to signed integers (such as int).
c unsigned ones-complement
c unsigned ones-complement
asked 1 hour ago
JL2210JL2210
623121
asked 1 hour ago
JL2210JL2210
623121
asked 1 hour ago
JL2210JL2210
623121
asked 1 hour ago
JL2210JL2210
623121
asked 1 hour ago
JL2210JL2210
623121
623121
Note that~0is a signed quantity — you'd need~0Uto make it unsigned.
– Jonathan Leffler
1 hour ago
Should I edit that?
– JL2210
1 hour ago
3
Since you've got some answers which addresses~0rather than~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.
– Jonathan Leffler
1 hour ago
add a comment |
Note that~0is a signed quantity — you'd need~0Uto make it unsigned.
– Jonathan Leffler
1 hour ago
Should I edit that?
– JL2210
1 hour ago
3
Since you've got some answers which addresses~0rather than~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.
– Jonathan Leffler
1 hour ago
Note that
~0 is a signed quantity — you'd need ~0U to make it unsigned.– Jonathan Leffler
1 hour ago
Note that
~0 is a signed quantity — you'd need ~0U to make it unsigned.– Jonathan Leffler
1 hour ago
Should I edit that?
– JL2210
1 hour ago
Should I edit that?
– JL2210
1 hour ago
3
3
Since you've got some answers which addresses
~0 rather than ~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.– Jonathan Leffler
1 hour ago
Since you've got some answers which addresses
~0 rather than ~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.– Jonathan Leffler
1 hour ago
add a comment |
3 Answers
3
active
oldest
votes
What's the difference between (size_t)-1 and ~0?
Type and value differ.
(size_t)-1 is the same value as SIZE_MAX and has a type of size_t.
~0 is often -1 and has the type of int.
Assigning both of those to a size_t will result in SIZE_MAX.
size_t a = (size_t)-1;
size_t b = ~0;
In the 2nd case, -1 is assigned to a b and undergoes a conversion first, wrapping around the -1 to the maximum size_t value.
answered 1 hour ago
chuxchux
85.3k874157
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
add a comment |
(size_t)-1 is of type size_t. It typically has a value of 232-1 or 264-1 (4294967295 or 18446744073709551615).
~0 is of type int, and has the value -1 on a 2's-complement system (i.e., just about everywhere).
Both are likely to have the same bit pattern -- if int and size_t are the same size, which they very commonly are not.
If you want the maximum value of type size_t, you can use the SIZE_MAX macro, defined in <stdint.h>. If you're using an older implementation (pre-C99) that doesn't provide SIZE_MAX, (size_t)-1 will work. I'm not sure why you'd want to write ~0 rather than -1 -- unless perhaps you're considering non-two's-complement systems.
edited 1 hour ago
Jonathan Leffler
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
Thanks for letting me know. I'll remember to defineSIZE_MAXin mystdint.himplementation.
– JL2210
1 hour ago
add a comment |
Note that the previous answers assume a 2s complement machine (very likely to be the case these days, but not guaranteed).
If you had a sign-magnitude machine then -1 would have a sign bit and least significant bit set with all others clear, if you had a 1s complement machine then -1 would have all bits but the LSB set.
In all of these cases (including the common 2s complement machine) ~0 has all bits set.
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
add a comment |
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
What's the difference between (size_t)-1 and ~0?
Type and value differ.
(size_t)-1 is the same value as SIZE_MAX and has a type of size_t.
~0 is often -1 and has the type of int.
Assigning both of those to a size_t will result in SIZE_MAX.
size_t a = (size_t)-1;
size_t b = ~0;
In the 2nd case, -1 is assigned to a b and undergoes a conversion first, wrapping around the -1 to the maximum size_t value.
answered 1 hour ago
chuxchux
85.3k874157
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
add a comment |
What's the difference between (size_t)-1 and ~0?
Type and value differ.
(size_t)-1 is the same value as SIZE_MAX and has a type of size_t.
~0 is often -1 and has the type of int.
Assigning both of those to a size_t will result in SIZE_MAX.
size_t a = (size_t)-1;
size_t b = ~0;
In the 2nd case, -1 is assigned to a b and undergoes a conversion first, wrapping around the -1 to the maximum size_t value.
answered 1 hour ago
chuxchux
85.3k874157
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
add a comment |
What's the difference between (size_t)-1 and ~0?
Type and value differ.
(size_t)-1 is the same value as SIZE_MAX and has a type of size_t.
~0 is often -1 and has the type of int.
Assigning both of those to a size_t will result in SIZE_MAX.
size_t a = (size_t)-1;
size_t b = ~0;
In the 2nd case, -1 is assigned to a b and undergoes a conversion first, wrapping around the -1 to the maximum size_t value.
answered 1 hour ago
chuxchux
85.3k874157
What's the difference between (size_t)-1 and ~0?
Type and value differ.
(size_t)-1 is the same value as SIZE_MAX and has a type of size_t.
~0 is often -1 and has the type of int.
Assigning both of those to a size_t will result in SIZE_MAX.
size_t a = (size_t)-1;
size_t b = ~0;
In the 2nd case, -1 is assigned to a b and undergoes a conversion first, wrapping around the -1 to the maximum size_t value.
answered 1 hour ago
chuxchux
85.3k874157
edited 1 hour ago
answered 1 hour ago
chuxchux
85.3k874157
answered 1 hour ago
chuxchux
85.3k874157
answered 1 hour ago
chuxchux
85.3k874157
85.3k874157
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
add a comment |
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
Comments are not for extended discussion; this conversation has been moved to chat.
– Bhargav Rao♦
50 mins ago
add a comment |
(size_t)-1 is of type size_t. It typically has a value of 232-1 or 264-1 (4294967295 or 18446744073709551615).
~0 is of type int, and has the value -1 on a 2's-complement system (i.e., just about everywhere).
Both are likely to have the same bit pattern -- if int and size_t are the same size, which they very commonly are not.
If you want the maximum value of type size_t, you can use the SIZE_MAX macro, defined in <stdint.h>. If you're using an older implementation (pre-C99) that doesn't provide SIZE_MAX, (size_t)-1 will work. I'm not sure why you'd want to write ~0 rather than -1 -- unless perhaps you're considering non-two's-complement systems.
edited 1 hour ago
Jonathan Leffler
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
Thanks for letting me know. I'll remember to defineSIZE_MAXin mystdint.himplementation.
– JL2210
1 hour ago
add a comment |
(size_t)-1 is of type size_t. It typically has a value of 232-1 or 264-1 (4294967295 or 18446744073709551615).
~0 is of type int, and has the value -1 on a 2's-complement system (i.e., just about everywhere).
Both are likely to have the same bit pattern -- if int and size_t are the same size, which they very commonly are not.
If you want the maximum value of type size_t, you can use the SIZE_MAX macro, defined in <stdint.h>. If you're using an older implementation (pre-C99) that doesn't provide SIZE_MAX, (size_t)-1 will work. I'm not sure why you'd want to write ~0 rather than -1 -- unless perhaps you're considering non-two's-complement systems.
edited 1 hour ago
Jonathan Leffler
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
Thanks for letting me know. I'll remember to defineSIZE_MAXin mystdint.himplementation.
– JL2210
1 hour ago
add a comment |
(size_t)-1 is of type size_t. It typically has a value of 232-1 or 264-1 (4294967295 or 18446744073709551615).
~0 is of type int, and has the value -1 on a 2's-complement system (i.e., just about everywhere).
Both are likely to have the same bit pattern -- if int and size_t are the same size, which they very commonly are not.
If you want the maximum value of type size_t, you can use the SIZE_MAX macro, defined in <stdint.h>. If you're using an older implementation (pre-C99) that doesn't provide SIZE_MAX, (size_t)-1 will work. I'm not sure why you'd want to write ~0 rather than -1 -- unless perhaps you're considering non-two's-complement systems.
edited 1 hour ago
Jonathan Leffler
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
(size_t)-1 is of type size_t. It typically has a value of 232-1 or 264-1 (4294967295 or 18446744073709551615).
~0 is of type int, and has the value -1 on a 2's-complement system (i.e., just about everywhere).
Both are likely to have the same bit pattern -- if int and size_t are the same size, which they very commonly are not.
If you want the maximum value of type size_t, you can use the SIZE_MAX macro, defined in <stdint.h>. If you're using an older implementation (pre-C99) that doesn't provide SIZE_MAX, (size_t)-1 will work. I'm not sure why you'd want to write ~0 rather than -1 -- unless perhaps you're considering non-two's-complement systems.
edited 1 hour ago
Jonathan Leffler
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
edited 1 hour ago
Jonathan Leffler
575k956881041
edited 1 hour ago
Jonathan Leffler
575k956881041
edited 1 hour ago
Jonathan Leffler
575k956881041
575k956881041
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
answered 1 hour ago
Keith ThompsonKeith Thompson
195k26290484
195k26290484
Thanks for letting me know. I'll remember to defineSIZE_MAXin mystdint.himplementation.
– JL2210
1 hour ago
add a comment |
Thanks for letting me know. I'll remember to defineSIZE_MAXin mystdint.himplementation.
– JL2210
1 hour ago
Thanks for letting me know. I'll remember to define
SIZE_MAX in my stdint.h implementation.– JL2210
1 hour ago
Thanks for letting me know. I'll remember to define
SIZE_MAX in my stdint.h implementation.– JL2210
1 hour ago
add a comment |
Note that the previous answers assume a 2s complement machine (very likely to be the case these days, but not guaranteed).
If you had a sign-magnitude machine then -1 would have a sign bit and least significant bit set with all others clear, if you had a 1s complement machine then -1 would have all bits but the LSB set.
In all of these cases (including the common 2s complement machine) ~0 has all bits set.
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
add a comment |
Note that the previous answers assume a 2s complement machine (very likely to be the case these days, but not guaranteed).
If you had a sign-magnitude machine then -1 would have a sign bit and least significant bit set with all others clear, if you had a 1s complement machine then -1 would have all bits but the LSB set.
In all of these cases (including the common 2s complement machine) ~0 has all bits set.
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
add a comment |
Note that the previous answers assume a 2s complement machine (very likely to be the case these days, but not guaranteed).
If you had a sign-magnitude machine then -1 would have a sign bit and least significant bit set with all others clear, if you had a 1s complement machine then -1 would have all bits but the LSB set.
In all of these cases (including the common 2s complement machine) ~0 has all bits set.
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
Note that the previous answers assume a 2s complement machine (very likely to be the case these days, but not guaranteed).
If you had a sign-magnitude machine then -1 would have a sign bit and least significant bit set with all others clear, if you had a 1s complement machine then -1 would have all bits but the LSB set.
In all of these cases (including the common 2s complement machine) ~0 has all bits set.
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
answered 2 mins ago
SoronelHaetirSoronelHaetir
7,1631514
7,1631514
add a comment |
add a comment |
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Note that
~0is a signed quantity — you'd need~0Uto make it unsigned.– Jonathan Leffler
1 hour ago
Should I edit that?
– JL2210
1 hour ago
3
Since you've got some answers which addresses
~0rather than~0U, best to leave it unchanged, I think, but note for the future that it is a good idea to be careful. You can change a question up until making the change would invalidate answers.– Jonathan Leffler
1 hour ago