ECE160 - Lesson 2
Operators, Precedence, Conditional Statements, Basic Input/Output
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
## Increment & Decrement Operators
## Increment & Decrement Operators * <code>i++</code> -- adds 1 to the variable after it is used * <code>++i</code> -- adds 1 to the variable before it is used * <code>i--</code> -- subtracts 1 to the variable after it is used * <code>--1</code> -- subtracts 1 to the variable before it is used
## Increment & Decrement Operators Example ``` #include <stdio.h> int main() { int i = 0; printf("%d\n", i); printf("%d\n", i++); printf("%d\n", ++i); i++; printf("%d\n", i--); printf("%d\n", --i); printf("%d\n", i--); printf("%d\n", i); return 0; } ```
## Bitwise Operators
## Bitwise Operators * <code>&</code> -- bitwise AND * <code>|</code> -- bitwise inclusive OR * <code>^</code> -- bitwise exclusive OR * <code><<</code> -- left shift * <code>>></code> -- right shift * <code>~</code> -- one's complement (unary)
## Bitwise Operators Example ``` #include <stdio.h> int main() { printf("5 & 4 = %d\n", 5 & 4); printf("5 | 4 = %d\n", 5 | 4); printf("5 ^ 4 = %d\n", 5 ^ 4); printf("5 << 2 = %d\n", 5 << 2); printf("12 >> 2 = %d\n", 12 >> 2); printf("~5 = %d\n", ~5); // Note 2's complement // 5 is 0000...0101 // Doing on's complement, we have // ~5 is 1111...1010 // which is MIN+sum(2^n) where n excludes n=0 and n=2 // Or simpler: -8 + 0 + 2 + 0 return 0; } ```
## Assignment Operators
## Assignment Operators * <code>i = i + 2 </code> is equivalent to <code> i += 2</code> * <code>i = i \* 2 </code> is equivalent to <code> i \*= 2</code> * <code>expr1 = (expr1) op (expr2)</code> is equivalent to <code>expr1 op= expr2</code> * Also works for: <code>* / % << >> & ^ |</code> * Commonly used in loops
## Precedence
## Precedence & Associativity Operators <img data-src="https://github.com/hong3cooper/ECE160B-Fall2018-Lesson2/blob/master/precedence.png?raw=true">
## Conditional Statements
## If Statements ``` if (a > b) { z = a; // do something } ``` * Example ``` #include <stdio.h> int main() { int a = 0; int b = 5; if (a < b) { printf("a is less than b\n"); } return 0; } ```
## If-Else Statements ``` if (a > b) { z = a; // do something } else { z = b; // do something else } ``` or ``` expr1 ? expr 2 : expr 3 ```
## If-Else Statement Example ``` #include <stdio.h> int main() { int a = 7; int b = 5; if (a < b) { printf("a is less than b\n"); } else { printf("a is greater than or equal to b\n"); } return 0; } ```
## If-Else If-Else Statements ``` if (a > b) { z = a; // do something } else if (a > c) { z = c; // do something } else { z = b; // do something else } ```
## If-Else If-Else Statement Example ``` #include <stdio.h> int main() { int a = 1; int b = 2; int c = 3; if (a < b) { printf("a is less than b\n"); } else if(a < c) { printf("a is less than c and greater than or equal to b\n"); } else { printf("a is greater than or equal to b and a is greater than or equal to c\n"); } return 0; } ```
## Basic Input/Output
## getchar * gets **one** character from the command line ``` #include <stdio.h> int main() { char c = getchar(); putchar(c); printf("%c", c); return 0; } ```