CS102B - Lesson 2

Types, Variables, Operators

Instructor: Professor Hong

## Review & Questions

## Type Conversions

## Adding a float and an int ``` #include <stdio.h> int main() { float f = 1.5f; int i = 3; int result = i + f; printf("%d", result); return 0; } ``` Note that precision is lost if storing in an int.

## Adding a float and an int ``` #include <stdio.h> int main() { float f = 1.5f; int i = 3; float result = i + f; printf("%f", result); return 0; } ``` Note that the int is implicitly convert to a float in the addition.

## Limits ``` #include <stdio.h> #include <limits.h> int main() { printf("CHAR_MIN: %d\n", CHAR_MIN); printf("CHAR_MAX: %d\n", CHAR_MAX); printf("SHRT_MIN: %d\n", SHRT_MIN); printf("SHRT_MAX: %d\n", SHRT_MAX); printf("INT_MIN: %d\n", INT_MIN); printf("INT_MAX: %d\n", INT_MAX); printf("UINT_MAX: %d\n", UINT_MAX); return 0; } ``` <a href="http://www.cplusplus.com/reference/climits/"> http://www.cplusplus.com/reference/climits/ </a>

## Wrapping ``` #include <stdio.h> int main() { char c = 'C'; printf("%c", c + 255); return 0; } ``` <a href="http://www.cplusplus.com/reference/climits/"> http://www.cplusplus.com/reference/climits/ </a>

## Casting * Not recommended as it is "hacky" * <code>(type-name) expression</code> * This will force the expression to be the type you specified

## Casting Example * Be **very** careful when casting types as it can lead to unexpected behaviors. ``` #include <stdio.h> #include <math.h> int main() { float f = 4.5f; double result = sqrt(f); printf("%f\n", result); double castResult = sqrt((int) f); printf("%f\n", castResult); return 0; } ```

## Relational & Logical Operators

## Relational & Equailty Operators Relational Operators: * <code>></code> -- greater than * <code>>=</code> -- greater than or equal to * <code><</code> -- less than * <code><=</code> -- less than or equal to Equality Operators: * <code>==</code> -- equal to; note that you use 2 = signs * <code>!=</code> -- not equal to These operators result in a boolean (true or false).

## Relational Operators Example ``` #include <stdio.h> #include <stdbool.h> int main() { bool b = 5 < 2; printf("%d", b); return 0; } ``` We generally don't print out bools like in the example above.

## Logical Operators: * <code>&&</code> -- logical and * <code>||</code> -- logical or * These operators also result in a boolean (true or false). * For numeric types, 0 is equivalent to false and any non-zero is true. * These are different from bitwise operations which we will learn later.

## Logical Operators Example ``` #include <stdio.h> #include <stdbool.h> int main() { bool b = (true && false); printf("%d", b); return 0; } ``` Note: We generally don't print out bools like in the example above.

## The Unary Operator '!' * Negates the boolean * <code>!0</code> -- true * <code>!1</code> -- false * <code>!100</code> -- false * <code>!(5 < 2)</code> -- true * <code>!((5 < 2) || !(3 < 1))</code> -- false