C# testing to see if a string is an integer?
Use the int.TryParse method. string x = “42”; if(int.TryParse(x, out int value)) // Do something If it successfully parses it will return true, and the out result will have its value as an integer.
integer
Java Integer compareTo() – why use comparison vs. subtraction?
This is due to integer overflow. When thisVal is very large and anotherVal is negative then subtracting the latter from the former yields a result that is bigger than thisVal which may overflow to the negative range.
Increment a Integer’s int value?
Integer objects are immutable, so you cannot modify the value once they have been created. You will need to create a new Integer and replace the existing one. playerID = new Integer(playerID.intValue() + 1);
How to do an Integer.parseInt() for a decimal number?
String s = “0.01”; double d = Double.parseDouble(s); int i = (int) d; The reason for the exception is that an integer does not hold rational numbers (= basically fractions). So, trying to parse 0.3 to a int is nonsense. A double or a float datatype can hold rational numbers. The way Java casts a … Read more
Finding the length of an integer in C
C: You could take the base-10 log of the absolute value of the number, round it down, and add one. This works for positive and negative numbers that aren’t 0, and avoids having to use any string conversion functions. The log10, abs, and floor functions are provided by math.h. For example: int nDigits = floor(log10(abs(the_integer))) … Read more
Catch and compute overflow during multiplication of two large integers
1. Detecting the overflow: x = a * b; if (a != 0 && x / a != b) { // overflow handling } Edit: Fixed division by 0 (thanks Mark!) 2. Computing the carry is quite involved. One approach is to split both operands into half-words, then apply long multiplication to the half-words: uint64_t … Read more
performance of unsigned vs signed integers
Division by powers of 2 is faster with unsigned int, because it can be optimized into a single shift instruction. With signed int, it usually requires more machine instructions, because division rounds towards zero, but shifting to the right rounds down. Example: int foo(int x, unsigned y) { x /= 8; y /= 8; return … Read more
What happens if I assign a negative value to an unsigned variable?
For the official answer – Section 4.7 conv.integral “If the destination type is unsigned, the resulting value is the least unsigned integer congruent to the source integer (modulo 2n where n is the number of bits used to represent the unsigned type). [ Note: In a two’s complement representation, this conversion is conceptual and there … Read more
Is there a built-in or more Pythonic way to try to parse a string to an integer
This is a pretty regular scenario so I’ve written an “ignore_exception” decorator that works for all kinds of functions which throw exceptions instead of failing gracefully: def ignore_exception(IgnoreException=Exception,DefaultVal=None): “”” Decorator for ignoring exception from a function e.g. @ignore_exception(DivideByZero) e.g.2. ignore_exception(DivideByZero)(Divide)(2/0) “”” def dec(function): def _dec(*args, **kwargs): try: return function(*args, **kwargs) except IgnoreException: return DefaultVal return … Read more
Why does the most negative int value cause an error about ambiguous function overloads?
This is a very subtle error. What you are seeing is a consequence of there being no negative integer literals in C++. If we look at [lex.icon] we get that a integer-literal, integer-literal decimal-literal integer-suffixopt […] can be a decimal-literal, decimal-literal: nonzero-digit decimal-literal ’ opt digit where digit is [0-9] and nonzero-digit is [1-9] and … Read more