C++ :: Assign Non-Number To Double Variable?
Jun 4, 2013
I am writing a math program, using variables of type double, and had initialized all variables to 0.0.
I now realize that not all results will be valid.
Is there a way to explicitly assign a variable of type double a non-numeric value, for example, "NaN", "Undefined", or "Unassigned" or something like that?
That way, when I read through the printout of results, I will realize the "NaN" results indicate a valid solution was not found. Whereas a 0.0 might not stand out.
I'd hate to have to go back and delete the initialization, and then re-assign 998 values just for the sake of 2 non-solutions.
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Nov 29, 2013
i want to assign number of bits by a variable in bitset? how to do that? like bitset<4> foo; instead of 4 i want to use some variable and later on by user i want to assign it! boost library or any other library!
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May 2, 2013
When I try to assign strings to a double pointer, it only prints out the last string when I try to print everything out, and then it segfaults.
Code:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <assert.h>
main(){
char **test = calloc(3,sizeof(char));
[Code] .....
Am I assigning something the wrong way? Also, I am trying to avoid using array notation in order to practice, at least for the assigning of the strings.
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May 10, 2013
I would like to convert a float or double variable into unsigned char variable and back.
float number_float = 23.453f;
unsigned char* number_char = (unsigned char*)malloc(sizeof(float));
number_char = reinterpret_cast<unsigned char*> (&number_float);
float* number_float_0 = reinterpret_cast<float*>(&number_char);
I am not getting the same value back.. why?
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Feb 3, 2014
I've been experimenting with pointers and am getting the below error.
'error: cannot convert 'int**' to 'int*' in assignment'
I thought it was ok to assign a variable address to another variable. Line 18 is where I get the error.
I am trying to show the progression of memory as I increment it as I have done on line 17 and again, I don't know why I don't see a progression through memory locations when output to the console on line 20.
Here's the code:
#include <iostream>
#include <cstring>
#include <cstdlib>
using namespace std;
int main() {
int *tt = new int;
int *p = new int;
[Code] .....
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May 26, 2013
Im starting with C. Like I said in the title, how do I assign the value from a function to a variable? I mean I have this function:
Code:
int EnteroAleatorio(){
rand();
return rand();
}
and I would like to assign the value of EnteroAleatorio to a variable in my main function, but when I try to do it and compile, I got the next error: non-lvalue in assignment
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Feb 22, 2014
I have to ask system (linux) for a value and then assign it to the variable.
Example:
unsigned char date[] = system("date");
Of course this is wrong, but illustrated what is my goal.
How to achieve this effect ? I've heard about POSIX but how to include and use it.
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Dec 25, 2014
What I'm trying to do is to assign the length of a string to an integer variable. This is what i tried, it did not work.
Code:
printf("Enter a string
");
fgets(test_pass, 30, stdin);
strcpy(x,(strlen(test_pass)));
printf("%d", x);
This was just a test, and it did not compile. How to do this?
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Jun 2, 2013
what I need is to get the first integer from a file and assign it to a variable and the others integers to an array. Example: Thats my file content 5 4 6 7 8 0 and that would be the code:
Code:
struct Array{
int n;
int *v;
}
[code]....
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Aug 22, 2012
I'm having some trouble with a variable from a database. That variable in that database is of type double.
To read from the database, I'm using a variable dr of type OleDbDataReader.
So far, I've been using dr["variablename"].ToString() to work with the variables from this database - without the ToString part it wasn't working.
However, with this specific variable (I'll call it "var"), I have to do numerical comparisons of >= and <=, so obviously, just using dr["var"].ToString() doesn't work.
Therefore, I tried creating a variable of type double called varConv and setting it as
varConv = Convert.ToDouble(drPen["var"].ToString()).
That doesn't work, gives me an error message saying "Input string was not in a correct format". If I remove the ToString part, it also doesn't work, with a different error message saying "Object cannot be cast from DBNull to other types".
Trying to do a direct comparison, as in dr["var"] >= x also doesn't work, says "Operator '>=' cannot be applied to operands of type 'object' and 'int' ".
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Feb 14, 2014
I have a string - a whole sentence that I want to assign a number to each letter, space, comma and period etc. So all "A's" will have the same number, all "B's" will have another number etc. I don't want to use the ASCII numbers because they all need to be sequential and some of the punctuation isn't. I have put the string into a char array to separate each character out and was thinking about running it through a loop with if statements for each letter and assigning numbers there and then saving the numbers in the order they appear into a list as a string but I keep coming up with errors so I don't know how to do it or if there is a better way to accomplish what I'm trying to do.
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Apr 4, 2014
Define a constant PI that has a value of 3.14159
- Create a double variable, Radius with an initial value of 10
- Create two double variables. Circum and Area, without initialization
- Using the following formulas, compute circumference and area of the circle:
circumference = pi * r * 2 (here, r means radius)
area = pi * r * r
- Display the result using three variables (numbers must come from variables)
- Expected output: (Don’t forget to display the period at the end of the first line)
Circle with radius of 10.
Circumference = 62.8318 Area = 314.159
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May 14, 2013
I am working on a project where I need to retrive a double number and store 8 bits of the number in one field and the other 16 bits in another field. the code below gives me an error.
lata= lat>>8;
latb = (lat & 0xff);
The error states that & and >> are illegal for double. With this in mind, can I use these on a double. If not what can I do to achieve what I am trying to do?
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Feb 19, 2014
So I have a template, part of a larger code, that is designed to calculate the number of multiplications it took to reach a certain number. The problem is, whenever I execute the program, mults is always printing out a strange number, perhaps its actual address.
template <class T>
T power3(T x, unsigned int n, unsigned int& mults) {
if (n == 0) return 1;
if (n == 1) return x;
if (n == 2){
[Code] ....
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Jun 9, 2013
How do i get the fraction for any decimal number in a variable?
Code: Code: #include<iostream>
using namespace std;
int main()
{
double x = 1/6;
cout << x;
cin.get();
}
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Feb 25, 2014
In C how can I initialize a variable that is not a letter or number? For example with a number I can :
Code:
int i = 5;
for ( i = 0; i <=5; i++ );
printf( "%d", i ) This would display a row of 5's
but what if I wanted to display a row of -----? What I am trying to do is read in a simple txt file, around the file I want ----1----2-----3 ect ect on the top ----a----b-----c down the side Then I want to be able to change the file at lets say position c2 and save it. This is the early stages of my attempt to set up a editable table.
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Apr 21, 2014
Write a function write with variable number of arguments that takes a string first argument followed by any number of arguments of type double and prints on the screen a string formatted by the rules described below. The first argument may contain formats in curly braces of the form {index[:specifier]}, where the square brackets show optional parts (this is :specifier may be missing), and index is the sequence number of an argument of type double (starting from sequence number 0).
Rules for formatting: In the printed string the curly brackets and their content will be replaced by the argument with the given index, formatted according to the given format specifier. If the format specifier is missing, the argument will be printed with its default format. For example:
write("The number {0} is greater than {1}.", 5, -3);
will print
The number 5 is greater than -3.
write("There are no format specifiers here.");
will print
There are no format specifiers here.
The format specifiers and their meanings are listed in the following table
Specifier MeaningFormat Output for 1.62 Output for 2.0
none default {0}1.62 2
ccurrency{0:c}$1.62 $2.00
escientific{0:e}1.620000e+000 2.000000e+000
ffixed point{0:f}1.620000 2.000000
iround to int{0:i}2 2
Limitations: You may limit the maximum number of arguments your function can process to a certain value, for example 10.
Suggested extensions:
-Add an optional alignment specification in the format , e.g., make the format of the form {index[,alignment][:specifier]}, where alignment is an integer specifying the width of the field in which the corresponding argument will be printed. If alignment is positive, align to the right, if it is negative, align to the left.
-Accept an optional integer after the specifier letter, specifying the required precision in the output. For example, {0:f2} will print the number 1.6234 as 1.62, but {0:f5} will print it as 1.62340.
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Oct 10, 2014
Im having trouble on getting the quantity up of the variable "item.iqty". For example the current quantity is 5 and in this function, the user inputs a number and it should add to the variable "item.iqty". So if if the user inputs 2 then the current quantity should be 7 now but in my program it hasnt changed. its still 5
void addQty(FILE *fp)
{
int num, qty, r, c, n;
bool found;
[Code]....
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Apr 23, 2013
I'm a basic C++ programmer, and I am stuck on this problem. You work for a company that collects a set of numbers. The numbers are located in a data file named "./Data_File". The data file contains two columns. how do you count a certain number on the left column.
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <iomanip>
using namespace std;
#define DATA_FILE1 "./Data_File"
#define SUCEESS 0
#define FAIL 1
[code].....
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Jan 9, 2015
how to make a program in which a user is prompted to input four numbers like 1234 and then print those four numbers one by one on screen using only one variable..??
For example:
1
2
3
4
in ascending order...
I've done that with two methods but i am not sure whether the methods were correct..
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Jul 18, 2014
I have a simple problem about memory allocation.In the function Nr_elements() i assign a value which represent the elements of array. The pointer p is initialised with the address of variable n, but when i compile i dont know why but dont work. This function return a pointer.
Code:
#include<stdio.h>
#include<stdlib.h>
int *Nr_elements();
int *allocate(int);
void deallocate(int *);
[code]....
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Mar 6, 2015
Program that has the user enter 5 digits then asks the user what they want to know about the 5 digits. My issue is when the program goes to print the value, its a totally ill related number
10 34 8 17 50
program prints out:
2 for smallest
79 for largest
119 for sum
23.80 for average
Code:
#include <stdio.h>#include <stdlib.h>
int main(void)
{
int smallNum, largNum, count=0, sum=0, value, choice;
double avgNum;
printf("Enter 5 integers
");
printf("
");
[Code]...
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Mar 3, 2013
I am forking 3 times in a loop like this but the variable "count" does not increment, it stays on '1' and therefore this is an infinite loop, and this simple thing dont make sense to me.
I have checked so that the pointer address is the correct one every loop.
Code:
void increase(int* x) {
*x += 1;
}
main() {
int pid, i, number = 0;
[Code] .....
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Mar 6, 2015
I need to create dynamic string by given format(%d,%s,%f,%lf,%c) using variable number of arguments in function. This code gives me an error(main.exe has stopped working):
Code:
#include<stdio.h>
#include<stdarg.h>
#include<string.h>
#include<stdlib.h>
char *form(char *format,...);
char *form(char *format,...)
[Code]...
I assume the error is in functions(itoa,fcvt,ecvt).
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Oct 23, 2014
I need to create a function that takes as an input a variable number of scalars and returns the biggest one. Just like std::max() does for 2 elements, but I need it for an undefined number of elements, can be 2, or 5, or 10 etc.. How to approach this?
What I need it for: I'm working with a bunch of vectors, maps, etc. and I need to find out which has the most elements. So I was thinking that I should end up with something like
int biggest = max(vector1.size(), vector2.size(), map1.size(), ...);
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Feb 24, 2013
Is it even possible to store the 100th Fibonacci number (beginning with the numbers 1 and 1) into a variable? I know the number is pretty huge, and wondered if there is a data type to hold a number that big.
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