C++ :: Evaluating Logical Boolean Expressions
Jan 10, 2013
I am looking for a library to aid me in evaluating Boolean expressions. For example, i have an expression like this:
(1*(5+3)+9*65/5-(354*4565*5643+98) >= 12345) && ( 654*987+123 || (2345 > 23423 && 1 != 2)))
(It can also be much longer!) and would like to evaluate them to a true/false boolean.
There are tons of libraries to calculate the (numerical) result of a mathematical expression, but this is not what i want to do.
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Dec 3, 2014
Also, can't use namespace std for this.
#include<iostream>
#include<stack>
#include<fstream>
#include<iomanip>
#include<queue>
#include<cassert>
[Code] ....
/* It will read in a infix expression from a text file.check if the parentheses in the input expression are balanced.convert the infix expression into a postfix expression and evaluate the expression.*/
int main() {
string expression;
string postfixExpression;
double result;
testBalanced();
[Code] ....
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Feb 25, 2013
I have the following code to calculate arithmetic expressions :
#include <iostream>
using namespace std;
using namespace std;
const char * expressionToParse = "6.5-2.5*10/5+2*5";
char peek(){
return *expressionToParse;
[code]....
The problem is that it does not work properly with decimal numbers for example it evaluates 6-2*10/5+2*5 = 12 which is correct but for 6.5-2.5*10/5+2*5 it returns 6 instead of 11.5 .
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Jun 8, 2013
Let's say I have a product that needs service after 500 hours at 100 RPM. I can dsiplay the remaining hours only as an integer and we only have integer math. Management wants it to display 500 for the first hour, not 499 after the first minute is ticked off. But after a few minutes fullHours will be 499 and partialHours will have some value. I have 3 ways to determine displayHours to suit management and I want to know if the first is ligit.
short fullHours = 500;
short partialHours = 0;
short displayedHours = 0;
// Method 1 - Is is Kosher to cast a boolean as an int? Is TRUE always a 1 or is that a bad assumption?
displayedHours = fullHours + (short) (partialHours != 0);
//Method 2 - Works but some have disdain for the ternary conditional
displayHours = fullHours + (partialHours ? 1 : 0);
//Method 3 - seems a bit pedantic
displayHours = fullHours;
if (partialHours != 0) {
displayHours++;
}
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Nov 3, 2013
i feel like im really close to completing this but i cant seem to get the result printed out i dont think im calling my evaluate function correctly and its not performing the operations..
#include <iostream>
#include <stack> //stack header file
using namespace std;
[Code].....
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Apr 12, 2015
I am trying to convert from infix to postfix, and then evaluating the postfix expression to get the final answer. I am having a severe problem though, because for somereason the conversion is not working at all. For example, when I input the first infix expression:
24 + 33 * ( 7 - 5 ) + 8 / 3 it ouputs 24 33 7 5 - 5 ) + 8 / 3( 7 - 5 ) + 8 / 3* ( 7 - 5 ) + 8 / 3+ 33 * ( 7 - 5 ) + 8 / 3 8 3/ 3+ 8 / 3
Which is obviously very wrong. I am not really sure where the problem is though.
Below I have included all of the code needed. I also had to create my own stack class, so I will include it too .
#include "stacks.h"
#include <iostream>
using namespace std;
bool IsOperand(char C) {
if(C >= '0' && C <= '9') return true;
if(C >= 'a' && C <= 'z') return true;
[Code] .....
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May 29, 2013
At one point in my C++, non-CLR program, the following code:
Code:
unsigned int size = 3;
float maxX = (float)(int(size-1))/2.0f;
std::cout << maxX;
outputs 107. Is it something about a conversion from unsigned int to float?
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Nov 27, 2014
Code:
int main() {
char *arr[] = {"Hello", "World", "Good", "Morning"};
display(arr);
return;
}
[code]....
The code works fine and prints the 4 strings. Where i m riddled is whether "ptr" in display function is a pointer or a string ? If it's a pointer then what is the type of the pointer? If it's an array, then as per my understanding, we cannot use an array name in expressions such as ptr++ (K&R).
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Dec 20, 2013
I wrote this program using an online compiler i am getting a lot of errors.
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int main() {
string birthmonth;
string birthday;
[Code] ....
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Mar 9, 2013
I've received a segmentation fault in this part of code:
Code:
for (; str[i] != ' ' || str[i] != ' '; i++) {
result[result_pos] = str[i];
result_pos++;
}
which, should mean:
Code: If str[i] is not equal to NULL character nor ' '; then, keep printing the chars within the word to variable result.
To understand what the function does, here's the whole code:
static char result[999];
/* char *split_word(const char *str, long n);
* Splits a string word-by-word. Where N is the word number. */
char *split_word(const char *str, long n) {
[Code]....
I'm trying to accomplish an easier way round to split string by word than using "strtok_r()". It might sound like "re-inventing the wheel", but... i will try to make it neat later.
The code looks okay, why would it segfault?
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Aug 25, 2014
I have this bit of code that I found here: [URL] and at first regex would work, but then when I hit "[]" it wouldn't. Here's the code:
#include <iostream>
#include <string>
#include <regex>
[Code]....
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May 11, 2013
I wrote this code to solve a problem in which the user inputs a permutation of size 'N' and the next permutation of the same elements has to be generated.
I went about this in this way: given 3 2 5 4 1, starting from the right, the first no. has to be searched which has a no. greater to it on its right. Here it is 2. Now an array is generated containing all no.s on its right and greater than it. For 2, it is: 5,4. Out of these the smallest member is searched for and switched with 2. So, 4 is switched with 2 to get the Next Permutation: 3 4 5 2 1.
The code I wrote does not show any error but does not return the correct value when run and gives the same value instead. If I enter '3 2 5 4 1' it returns the same value as the answer.
#include<iostream.h>
#include<conio.h>
void main() {
clrscr();
int N,M,i,n,c,swap,flag,count,small,m;
int Array[100],Key[100];
[Code] .....
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Oct 7, 2014
int main()
{
char rORc, choice;
int sizerc;
[Code]....
when I input the character which is the underscore, and the row # it should display the table and sort that specific row. Why is the if statement skipped? This is not the complete program but has everything needed.
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Mar 31, 2015
I get the following error:
Cannot convert lambda expression to type system delegate because it's not a delegate type (on invoke).
The Second error is: Client.PrivateChat.txtReceive is inaccessible due to its protection level..
private PrivateChat pChat;
private void client_Received(Client sender, byte[] data) {
this.Invoke(() =>
{
for (int i = 0; i < clientList.Items.Count; i++) {
var client = clientList.Items[i].Tag as Client;
if (client == null || client.Ip != sender.Ip) continue;
[Code] .....
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Nov 15, 2013
My project is on an online shop in which you can manage a shop(adding ,deleting ,clearing and modifying items) also you can switch to different shops(all shops are same)
Code:
#include<iostream>
#include<fstream>
#include<conio.h>
#include<stdlib.h>
#include<string.h>
[Code] ....
The logical problem is serious because i am not able to find the error!!! There is some problem with display lines in void shop()-->if(mode=='s') and if(mode=='d'). I add only one item but in output screen i see two items(sometimes >2)
*note* to run the above display lines in the output screen....first register--->add atleast one item--->see your shop
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Sep 5, 2013
So I need to use boost/regex for regular expressions. someone told me that it needs to be built. the first problem is boost doesn't tell you how to build it and the second is i did sudo apt-get install libboost something. I don't remember the exact name of the package. it installed but i dont know how i would build it when its installed.
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Dec 11, 2013
writing a program for "Validating the e-mail id without using regular expressions in c/c++"?
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Apr 9, 2015
#include <iostream>
using namespace std;
int main(){
int polje[8][8];{
for(int i=0;i<8;i++)
for(int j=0;j<8;j++) {
[Code] .....
I don't get any errors,the program works. The problem is that it doesnt work how it should. This is a simple program that multiplies 2 variables(i and j)that go from 0 to 7. The problem I have is with the logical operators,i want the program to skip multiplication with 0 and when the 2 variables are the same value. When i try using only 1 logical operator it work.
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May 22, 2014
In order to parse mathematical expressions I am trying regular expressions and a recursive algorithm, but I have a problem with the four basic operations: +, -, *, /.
Trying to analyze a string like "a+(b+c)", if I use the pattern for a sum "(.+)+(.+)" the program matches it recognizing as subpatterns: "a+(b" and "c". How could I achieve the program to try also the other possibility?
I think that it would be great something like an regex_iterator which worked with regex_match instead of regex_search. I mean, an iterator that iterates over all the possible ways to match a given regular expression and a given string. This way I could loop through all these possibilities until the two subpatterns produced were correct mathematical expressions.
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Oct 31, 2014
I have to write a program that does the following: Monkey Business A local zoo wants to keep track of how many pounds of food each of its three monkeys eats each day during a typical week. Write a program that stores this information in a two-dimensional 3 - 7 array , where each row represents a different monkey and each column represents a different day of the week. The monkeys are represented by integers 1, 2, and 3; the weekdays are "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday". The program should first prompt the user to input the data for each monkey, starting with "Sunday" for monkey #1, then monkeys #2 and #3, followed by "Monday" for monkey #1, then monkeys #2 and #3 and so on, through "Saturday". The program then creates a report that includes the following information, each properly labeled (see below):
-Average amount of food eaten per day by the whole family of monkeys.
-The least amount of food eaten during the week by any one monkey.
-The greatest amount of food eaten during the week by any one monkey.
Input Validation: Do not accept negative numbers for pounds of food eaten. When a negative value is entered, the program outputs "invalid (negative) food quantity -- re-enter" and attempts to reread the value . Prompts And Output Labels: Decimal values should be displayed using default precision, i.e. do not specify precision. Each item read should be prompted for by a string of the form "Enter the food eaten by monkey #N on DAY:" when N is 1 or 2 or 3 and DAY is "Sunday" or "Monday" or ... or "Saturday".
The output should be of the form:
Average food consumed daily: 6.23
The least daily food consumed was by Monkey #0 on Friday
The most daily food consumed was by Monkey #2 on Sunday where the specific amount of food or specific monkeys or specific days identified depend on the actual input.
However after the process of resolving the errors unable to convert to standard string and unresolved externals I now have a logical error that causes the output of the DAYNAME variable to output as what appears to be hex in the following picture:
How I can fix this and why it's casting them as this in the output.
My full code is as follows because I don't know exactly, which line of code is causing this to happen:
Code:
//
#include <iostream>
#include <iomanip>
#include <string>
using namespace std;
// constants
const int MONKEYS = 3;
const int DAYS = 7;
[Code] .....
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May 26, 2013
If input value was shifted to the right on bit level. How can I determine whether a logical or arithmetic shift is performed.
Code:
#include <stdio.h>
#include <stdlib.h>
void main ()
[Code]......
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Sep 16, 2014
Can I use Shunting-yard algorithm to evaluate Expressions (arithmetic, relational, and logical) ?
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Dec 1, 2014
This is an example of how sub string and math can be used to make logical decisions without using if/elses or switches. It works because of this equation
(x + |x|)/x = 2 if x > 0 and = 2 if x < 0.
#include <iostream>
#include <string>
#include <cmath>
using namespace std;
int main() {
//declaration of variables
[Code] ....
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Feb 22, 2015
1) ask the user to input a mathematical expression in the following format:
NUMBER Operator NUMBER Operator NUMBER
Example: 17 + 15 - 3
Example: 2 * 3 - 4
How to output the answer of the users equation. Is there a function that includes all math operators (+,-,/,*)? Would i need to write each possible scenario using if statements?
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Dec 5, 2014
i have stuck in a join and i cant figure out where the problem is, i have those tables
public class Themes
{
[PrimaryKey, AutoIncrement]
public int Id { get; set; }
[Code].....
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Apr 28, 2015
I have two questions that are related to each other. The first one is about overloading the addition operator.
I have defined a struct as the following:
Code:
#include <iostream>
#include <string>
struct Sales_data {
[Code] ....
I then overloaded the I/O operators so I could print to the screen information related Sales_data.
Code:
// overload ostream in order for cout to work
std::ostream& operator << (std::ostream & out,
const Sales_data & cSales_data) {
out << cSales_data.bookNo << ", " << cSales_data.units_sold << ", "
[Code] ....
My first issue is with overloading the addition operator. Everyone works correctly except for std::cout << item << std:endl; will no not output the ISBN number only the units_sold and revenue when added together.
Code:
// addition operator rules
Sales_data Sales_data::operator + (const Sales_data & data2) {
units_sold += data2.units_sold;
revenue += data2.revenue;
return *this;
}
Now here is the code in its entirety
Code:
#include <iostream>
#include <string>
// Sales_data structure
struct Sales_data {
std:: string bookNo;
unsigned units_sold = 0;
[code] .....
After total = total + item;, I would like to print the total for this particular ISBN. However, I only get: blank, total units, total revenue where blank is where the ISBN would go but doesn't print after addition. My second question has to do with comparing the ISBN's of the books entered during the while loop. I would like to do something like
Code:
if (item_i.bookNo == item_i+1.bookNo) {
total = total + item;
} else {
std::cerr << "Books entered must have the same ISBNs" << std::endl;
}
Unfortunately, I cannot figure out how to set up a comparison of the bookNos. If I used #include <casset> in the overload + rule, it will immediately exit since I have no way to compare the ISBNs.
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