divide-by-zero

问题 My toy compiler crashes if I divide by zero in a constant expression: int x = 1 / 0; Is this behaviour allowed by the C and/or C++ standards? 回答1: The mere presence of 1 / 0 does not permit the compiler to crash. At most, it is permitted to assume that the expression will never be evaluated, and thus, that execution will never reach the given line. If the expression is guaranteed to be evaluated, the standard imposes no requirements on the program or compiler. Then the compiler can crash. 1 /

问题 Everybody knows you're not supposed to compare floats directly, but rather using a tolerance: float a,b; float epsilon = 1e-6f; bool equal = (fabs(a-b) < epsilon); I was wondering if the same applies to comparing a value to zero before using it in division. float a, b; if (a != 0.0f) b = 1/a; // oops? Do I also need to compare with epsilon in this case? 回答1: Floating point division by zero is not an error. It raises a floating point exception (which is a no-op unless you're actively checking

问题 I have the following code: scores = [matrix[i][i] / sum(matrix[i]) for (i, scores) in enumerate(matrix)] My problem is that sum(matrix[i]) could be 0 in some cases, resulting in a ZeroDivisionError . But because matrix[i][i] is also 0 in that case, I solved this as follows: scores = [divide(matrix[i][i], sum(matrix[i])) for (i, scores) in enumerate(matrix)] The function divide(x, y) returns 1 if y == 0 and (x / y) if y > 0 . But I wonder if there is an easier way. Maybe I could use some

问题 Why C# allows: 1.0 / 0 // Infinity And doesn't allow: 1 / 0 // Division by constant zero [Compile time error] Mathematically, is there any differences between integral and floating-point numbers in dividing by zero? 回答1: According to Microsoft, "Floating-point arithmetic overflow or division by zero never throws an exception, because floating-point types are based on IEEE 754 and so have provisions for representing infinity and NaN (Not a Number)." More on this here. 回答2: Mathematically,

问题 The following compiles fine in my Eclipse: final int j = 1/0; // compiles fine!!! // throws ArithmeticException: / by zero at run-time Java prevents many "dumb code" from even compiling in the first place (e.g. "Five" instanceof Number doesn't compile!), so the fact this didn't even generate as much as a warning was very surprising to me. The intrigue deepens when you consider the fact that constant expressions are allowed to be optimized at compile time: public class Div0 { public static

问题 The following compiles fine in my Eclipse: final int j = 1/0; // compiles fine!!! // throws ArithmeticException: / by zero at run-time Java prevents many "dumb code" from even compiling in the first place (e.g. "Five" instanceof Number doesn't compile!), so the fact this didn't even generate as much as a warning was very surprising to me. The intrigue deepens when you consider the fact that constant expressions are allowed to be optimized at compile time: public class Div0 { public static

问题 I'm using basic .net DataColumns and the associated Expression property. I have an application which lets users define which columns to select from a database table. They can also add other columns which perform expressions on the data columns resulting in a custom grid of information. The problem I have is when they have a calculation column along the lines of "(C2/C3)*100" where C2 and C3 are data columns and the value for C3 is zero. The old "divide by zero" issue. The simple answer would

问题 Hope your well. I am working on a report and seem to get a #error. Seems like it is a divide by zero error but I can not work out a solution. The expression: =( Sum(Fields!Line_Sell.Value) - Sum(Fields!Line_Cost.Value) ) / Sum(Fields!Line_Sell.Value) I am relatively new to RS but have tried ISNULL( ) but with no success. Any help, I would be greatful. Thanks 回答1: Let's say you have an expression set to x / y, where y has the potential to be zero. As you experienced, SSRS will change this

问题 After having searched around a little bit, I'm still struggling with divisions by zero in numpy. I am stunned by the contradiction I report right away: from numpy import * seterr(all='ignore') # Trying to avoid ZeroDivisionError, but unsuccessful. def f(x) : return 1./(x-1.) With this, when I execute f(1.) , I get ZeroDivisionError: float division by zero . However, when I define z = array( [ 1., 1. ] ) and execute f(z) , I do not get any error, but array([ inf, inf]) . As you can see, there

问题 I have the following code as part of a function: px = x2 - x1 py = y2 - y1 pz = z2 - z1 div = px*px + py*py u = ((x0 - x1) * px + (y0 - y1) * py) / div the u= line returns RuntimeWarning: invalid value encountered in divide when run. This is because occasionally the div= line returns zero. However, if I rewrite the u= line as: u = np.where(div != 0, ((x0 - x1) * px + (y0 - y1) * py) / div, 0) it still returns the same runtime warning. This code outputs the desired numbers however I thought