bool-and-or – Conjunction and disjunction – Computer Science by Example

bool-and-or – Conjunction and disjunction

Boolean values are those which have a value of true or false. (cf. “4.1. Data types” and “Boolean operators and comparison operators”.) Given two boolean values, we can perform and/or operations or conjunction/disjunction operations:

The result of a conjunction is true if and only if both boolean operands are true.
The result of a disjunction is false if and only if both boolean operands are false.

Write a program that reads several and/or conjunction/disjunction operations and prints their result.

Input and output

Input will consist of several lines each containing a boolean p, an operator x and a boolean q separated by a single space. Booleans p and q are either of the strings true or false and the operator x is either of the strings and or or. For each line of input, there should be a line of output containing a line with the result of the given input operation.

Example input

true and false
false or true

Example output

false
true

The `conjunction` and `disjunction` functions

The submitted program should contain the conjunction and disjunction functions that receive two boolean as arguments and return a boolean. Please refer to the information for the chosen language:

Python definitions: def conjunction(p, q): and def disjunction(p, q):
C prototypes: int conjunction(int p, int q); and int disjunction(int p, int q);
Haskell type: conjunction, disjunction :: Bool -> Bool -> Bool
C++ prototypes: bool conjunction(bool p, bool q); and bool disjunction(bool p, bool q); (see hint below)
C# definitions: public static bool Conjunction(bool p, bool q) and public static bool Disjunction(bool p, bool q) in a public class Program.
Java definitions: public static boolean conjunction(boolean p, boolean q) and public static boolean disjunction(boolean p, boolean q) in a public class BoolAndOr.
JavaScript definitions: function conjunction(p,q) and function disjunction(p,q)
Lua definitions: function conjunction (p, q) and function disjunction (p, q)
Ruby definitions: def conjunction(p, q) and def disjunction(p, q)

Scoring

1/6: works for the above example but produces output in an incorrect format
2/6: works for the above example and produces output in the correct format
6/6: works for other test cases

Hints

Comparing strings to arrive at a bool. You can use string equality to create a boolean value from strings.

In Python and Haskell, you can compare strings s1 and s2 using the equality operator:
```
 s1 == s2
```
This operator also works with literal strings:
```
 str == "hello"
```
In C, you can compare strings using the strcmp function:
```
 strcmp(s1, s2) == 0
```
When the result of strcmp is 0 that means the given strings are equal. The strcmp function also works with literal strings:
```
 strcmp(str, "hello") == 0
```
What are booleans? Read both “4.1. Data types” and “Boolean operators and comparison operators” sections of the Computer Science by Example book for an explanation of what are booleans and how to use them in programming.
Beware of the data types. Users of Python and dinamically-typed languages beware. The conjunction and disjunction functions will be tested with proper boolean values as their arguments and not with booleans encoded in strings. This is similar to how the add function of earlier exercises add1 and add does take proper integer values and not integer values encoded as strings.

In Python, there is a distinction between the boolean value False and the string 'False'. Confusingly enough, in Python 'False' has a boolean value of True:
```
>>> bool('False')
True
```
This comes from the fact that in Python, boolean conversion from strings defaults to treating empty strings as False-valued and non-empty strings as True-valued. This similar to the distinction between the integer 12 and the string "12".
C++ namespace conflicts. If you are facing namespace conflicts locally, read on. Starting with C++17, the std namespace does export two names called conjunction and disjunction. In this exercise, you should avoid using namespace std; and import required std symbols one by one:
```
 using std::cin;
 using std::cout;
```
Or, you can simply prefix all uses with std::, e.g.: std::cin and std::cout.

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