Strings, Boolean expressions

Strings, Boolean expressions#

Strings#

#include <stdio.h>
#include <string.h>
#define STR_SIZE 100

auto firstName = "Ada";
auto lastName = "Lovelace";
char fullName[STR_SIZE];

// Multiline string with interpolation (Raw string literals)
auto table = R"(
+---+---+---+---+
| x |   | x |   |
| y |   |   |   |
+---+---+---+---+
)";

int main() {
  // Length of string
  printf("First name length %lu\n", strlen(firstName));

  // Comparing
  if (strcmp(firstName, lastName) == 0)
    puts("Same word");
  else
    puts("Different names");

  // Simple concatenation
  strcat(fullName, firstName);
  strcat(fullName, " ");
  strcat(fullName, lastName);
  puts(fullName);

  // More readable using a format string
  sprintf(fullName, "%s %s", firstName, lastName);
  puts(fullName);

  puts(table);
}

Activity 16

Peek into string.h in the standard library. Select function/s which can be useful for finding a string in an array of strings.

3 min

Boolean expressions#

The questions we had previously are in fact boolean expressions.

Boolean expression

an expression that produces a Boolean value. Such a value is either true or false.

Examples#

// Simple boolean comparisons
bool isEqual = 5 == 5;            // true
bool isNotEqual = 5 != 5;         // false
bool isGreater = 10 > 5;          // true
bool isLess = 5 < 10;             // true
bool isGreaterThanEqual = 5 >= 5; // true
bool isLessThanEqual = 10 <= 5;   // false

// Combination operators
bool andCondition = 5 > 3 && 10 < 20; // true (both must be true)
bool orCondition = 5 > 10 || 3 < 4;   // true (enough if one is true)
bool notCondition = !(5 == 5);        // false (negation)

int main() {
  // Practical example: Check if a number is within a range
  auto number = 7;
  bool isInRange = number > 5 && number < 10; // true
}

We can use the Boolean expression on the right of the equal sign = in the if statement.

Activity 17

Which of the following are Boolean expressions and evaluate to false, assuming the following initialization code? The statements in the choices do not affect others.

auto t = true;
auto f = false;
auto c = 3;
auto i = 9;
auto k = 11;

Choices:

  1. t == f

  2. t = f

  3. i >= c && k > i

  4. !t

  5. k != 11

  6. 10 < c || c <= 20

Contents