CSI 1430 Exam 3: IF-ELSE Branches and Equality

• CSI 1430 Mastery Exam 3 study notes

IF-ELSE Branches (General)

• Branch = sequence of statements executed under a condition.
• If branch = branch only taken if an expression is true
• If-Else Branch = has two branches
• The first branch executes if an expression is true
• Else the other branch is executed

Detecting Equal Values with Branches

• If Statement = executes a group of statements if an expression is true
  • Surrounded by Braces {} which represent a grouping, such as statements
• Equality Operator (==) = results in true if the left and right sides are equal
• Inequality Operator (!=) = results in true if the left and right sides are not equal, or different
• Expressions involving these operators evaluates to a Boolean
• Boolean = a type that has just two values, true or false
• If-Else Statement = executes one group of statements when an expression is true, and another group of statements when the expression is false
  • Nested If-Else Statements = if-else statements WITHIN an if-else statement
• Relational and Equality operators can work for integer, character, and floating-point built-in types
• Compares ASCII numerical encoding
• Floating-point types should not be compared using the equality operators because of the imprecise representation of floating-point numbers
• Can also be used for string type
• Strings are equal if they have the same number of characters and corresponding characters and are identical

Detecting Ranges with Branches

• Relational Operator = checks how one operand's value relates to another, like being greater than
  • Some operators involve two characters in a specific order
  • a < b means a is less than b
  • a > b means a is greater than b
  • a <= b means a is less than or equal to b
  • a >= b means a is greater than or equal to b

Detecting Ranges Using Logical Operators

• Logical Operator = treat operands as being true or false, and evaluates to true or false.
• a AND b or a && b returns true when both of its operands are true
• a OR bora || b returns true when at least one of its two operands are true
• NOT a or !a returns true when its one operand is false, and vice-versa

Order of Evaluation

• Precedence Rules = the order in which operators are evaluated in an expression:
• () Parentheses
• ! Logical NOT
• */%+- Arithmetic Operators (using their precedence rules)
• () Parenthesis
• Unary -
• */% Complex Arithmetic
• • • Simple Arithmetic
• Left-To-Right
• < <= > >= Relational Operators
• == != Equality and Inequality Operators
• && Logical AND
• || Logical OR
• Bitwise Operators = using a singular & or | when trying to use logical operators, may yield different behavior

Switch Statements

• Switch = clearly represents multi-branch behavior involving a variable being compared to constant values
• Case = each scenario whose constant expression matches the value of the switch expression
• If no case matches, then the default case statements are executed

Omitting The Break Statement

• Omitting Break will cause the statements within the next case to be executed, but may be useful when multiple cases should yield the same result

Boolean Data Type

• Boolean = refers to a quantity that has only two possible values, true or false (bool)
  • isWeekend = true
  • isLargeParty = (partySize > 6)

String Comparisons

• Equal strings have the same number of characters, and each corresponding character is identical
• String Comparison: Relational
• Begins at index 0, and compares each character until the evaluation results in false, or the end of a string is reached
• 'A' is 65, 'B' is 66, etc, while 'a' is 97, 'b' is 98, etc.
  • “Apples" is less than “apples” because 65 is less than 97
• If existing characters are equal, the shorter string is less than

String Access Operations

• String = a sequence of characters in memory
  • Each string character has a position number called an index, starting with 0
• at() = the notation someString.at(x) accesses the character at index x of a string
  • A character in a string can be assigned (e.g., userString.at(3) = 'X'; changes userString to “abcXe”)
• size() = returns the string's length
• push_back() = adds a character to the end of a string
• append() = adds one string to the end of another
• The + operator can return a new string with one string appended to another string
• size() and length() both return string length

Common Errors

• Exception = detected runtime error that often prints an error message and terminates the program
  • .at generates an exception if the index is out of range for the string's size
  • Brackets are allowed (ex. someString[0]) but doesn't provide error checking

Character Operations

• cctype library (#includ ) = character type
  • isalpha(c) = returns true if alphabetic
  • isdigit(c) = returns true if a digit
  • isspace(c) = returns true if whitespace
  • toupper(c) = returns uppercase version of that index (letter = toupper('a'))
  • tolower(c) = returns lowercase version of that index (letter = tolower('A'))

Finding, Inserting and Replacing Text in a String

• find() = used to find a string or character in a string (s1.find(textToFind))
  • textToFind can be a string or character
  • string::npos = special value representing “no position”
• find(textToFind, startIndex) = returns the index of the first occurrence of textToFind starting at index startIndex instead of index 0

Getting a Substring

• Substring = a contiguous part of a string (“world” is a substring of “Hello world”)
  • substr() = used to get a substring of a string (s1.substr(startIndex, numCharacters))

Inserting and Replacing Text in a String

• insert() = inserts text into a string (s1.insert(startIndex, newText))
• replace() = replaces text in a string (s1.replace(startIndex, numCharacters, newText))

Conditional Expressions

• Conditional expression = has the form: condition ? exprWhenTrue : exprWhenFalse
• If the condition evaluates to true, exprWhenTrue is evaluated
• If the condition evaluates to false, then exprWhenFalse is evaluated
• Ternary operator used the “?” and “:” in the conditional expression

Floating-Point Comparison

• Floating-point numbers should not be compared using == because they cannot be exactly represented
  • Use < 0.0001 and fabs()
  • Epsilon = difference threshold indicating that floating-point numbers are equal
  • Floating point numbers are not always stored with 100% accuracy

Short Circuit Evaluation

• Short circuit evaluation = skips evaluating later operands if the result of the logical operator can already be determined
  • AND short circuits if the first operand evaluates to false
    • True && operand2 => If the first operand evaluates to true, operand2 is evaluated
    • False && operand2 => If the first operand evaluates to false, the result is always false, so operand2 is not evaluated
  • OR short circuits to true if the first operand is true
    • True || operand2 => If the first operand evaluates to true, the result is always true, so operand2 is not evaluated
    • False || operand2 => If the first operand evaluates to false, operand2 is evaluated

Study notes covering IF-ELSE branches, including the use of equality (==) and inequality (!=) operators in conditional statements. Also covers Boolean expressions and nested IF-ELSE structures. For CSI 1430 Exam 3.