unsigned-integer | 易学教程

Why is size_t unsigned?

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Bjarne Stroustrup wrote in The C++ Programming Language: The unsigned integer types are ideal for uses that treat storage as a bit array. Using an unsigned instead of an int to gain one more bit to represent positive integers is almost never a good idea. Attempts to ensure that some values are positive by declaring variables unsigned will typically be defeated by the implicit conversion rules. size_t seems to be unsigned "to gain one more bit to represent positive integers". So was this a mistake (or trade-off), and if so, should we minimize use of it in our own code? Another relevant article

Using MySQL's TIMESTAMP vs storing timestamps directly

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问题 I\'m in a dilemma about saving date and time values in MySQL\'s TIMESTAMP format vs in a custom UNSIGNED INT format. The main considerations here are speed of retrieval, appropriate range calculations in PHP and occasional formatting into human readable values. The storage space required for each type and their ranges: DATETIME 8 bytes \'1000-01-01 00:00:00\' to \'9999-12-31 23:59:59\' TIMESTAMP 4 bytes \'1970-01-01 00:00:01\' UTC to \'2038-01-19 03:14:07\' UTC UNSIGNED INT 4 bytes (Maximum

What is the benefit of zerofill in MySQL?

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I just want to know what is the benefit/usage of defining ZEROFILL for INT DataType in MySQL ? `id` INT UNSIGNED ZEROFILL NOT NULL When you select a column with type ZEROFILL it pads the displayed value of the field with zeros up to the display width specified in the column definition. Values longer than the display width are not truncated. Note that usage of ZEROFILL also implies UNSIGNED. Using ZEROFILL and a display width has no effect on how the data is stored. It affects only how it is displayed. Here is some example SQL that demonstrates the use of ZEROFILL: CREATE TABLE yourtable (x INT

Why are unsigned int's not CLS compliant?

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Why are unsigned integers not CLS compliant? I am starting to think the type specification is just for performance and not for correctness. Not all languages have the concept of unsigned ints. For example VB 6 had no concept of unsigned ints which I suspect drove the decision of the designers of VB7/7.1 not to implement as well (it's implemented now in VB8). To quote: http://msdn.microsoft.com/en-us/library/12a7a7h3.aspx The CLS was designed to be large enough to include the language constructs that are commonly needed by developers, yet small enough that most languages are able to support it.

Overflowing of Unsigned Int

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问题 What will the unsigned int contain when I overflow it? To be specific, I want to do a multiplication with two unsigned int s: what will be in the unsigned int after the multiplication is finished? unsigned int someint = 253473829*13482018273; 回答1: unsigned numbers can't overflow, but instead wrap around using the properties of modulo. For instance, when unsigned int is 32 bits, the result would be: (a * b) mod 2^32 . As CharlesBailey pointed out, 253473829*13482018273 may use signed

unsigned int and signed char comparison

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问题 I am trying to compare an unsigned int with a signed char like this: int main(){ unsigned int x = 9; signed char y = -1; x < y ? printf(\"s\") : printf(\"g\"); return 0; } I was expecting the o/p to be \"g\". Instead, its \"s\". What kind of conversion is done here? 回答1: Section 6.3.1.8 , Usual arithmetic conversions, of C99 details implicit integer conversions. If both operands have the same type, then no further conversion is needed. That doesn't count since they're different types.

A warning - comparison between signed and unsigned integer expressions

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问题 I am currently working through Accelerated C++ and have come across an issue in exercise 2-3. A quick overview of the program - the program basically takes a name, then displays a greeting within a frame of asterisks - i.e. Hello ! surrounded framed by *\'s. The exercise - In the example program, the authors use const int to determine the padding (blank spaces) between the greeting and the asterisks. They then ask the reader, as part of the exercise, to ask the user for input as to how big

What is the benefit of zerofill in MySQL?

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问题 I just want to know what is the benefit/usage of defining ZEROFILL for INT DataType in MySQL ? `id` INT UNSIGNED ZEROFILL NOT NULL 回答1: When you select a column with type ZEROFILL it pads the displayed value of the field with zeros up to the display width specified in the column definition. Values longer than the display width are not truncated. Note that usage of ZEROFILL also implies UNSIGNED. Using ZEROFILL and a display width has no effect on how the data is stored. It affects only how it

Why are unsigned int's not CLS compliant?

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问题 Why are unsigned integers not CLS compliant? I am starting to think the type specification is just for performance and not for correctness. 回答1: Not all languages have the concept of unsigned ints. For example VB 6 had no concept of unsigned ints which I suspect drove the decision of the designers of VB7/7.1 not to implement as well (it's implemented now in VB8). To quote: http://msdn.microsoft.com/en-us/library/12a7a7h3.aspx The CLS was designed to be large enough to include the language