The conditional branch operator if-else. Types of conditional branch operators
Contents
- 1. Operator of conditional branch if-else. Types of conditional branch operators. The purpose
- 2. Abbreviated form of the conditional branch operator: if
- 3. Full form: if-else
- 4. Ladder (calcade) form: if-else-if
- 5. Examples of using the if statement (short form)
- 6. Examples of using the if-else operator (full form)
- 7. Examples of using the operator if-else-if (ladder form)
- Related topics
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1. Operator of conditional branch if-else. Types of conditional branch operators. The purpose
In the Kotlin programming language, there are tools that change the computational process depending on the fulfillment of a certain condition.
Such means include the if-else operator.
The conditional branch operator has 3 forms:
- abbreviated form if;
- full form if-else;
- ladder form if-else-if.
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2. Abbreviated form of the conditional branch operator: if
The general form of the abbreviated form of the conditional jump operator is as follows
if (condition)
statement;
here
- condition – a conditional expression that returns a Boolean result. If the value of the conditional expression is true, then the statement is executed. If condition is false, then nothing is executed (the statement following the if statement is executed);
- statement – some operator.
If you need to execute several statements in the abbreviated if statement, then according to the Kotlin syntax, these statements are enclosed in curly braces { }. In this case, the general form of the if statement is:
if (condition) { // statements // ... }
Figure 1 shows a schematic representation of the abbreviated form of an if statement.
Figure 1. The abbreviated form of the if statement
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3. Full form: if-else
The full form of the conditional branch operator is
if (condition) { // statements if condition=true // ... } else { // statements if condition=false // ... }
here
- condition – a conditional expression, the value of which determines which group of statements will be executed. If condition = true, then statements after the if keyword are executed. Otherwise, the statements after the else keyword are executed.
If only one statement needs to be executed after the if or else keyword, then the curly braces {} can be omitted.
Figure 2 shows a graphical representation of the if-else operator.
Figure 2. Statement if-else. Graphic designation
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4. Ladder (cascade) form: if-else-if
The general syntax of the ladder form of the if-else-if conditional statement is as follows
if (condition1) { // statements1 // ... } else if (condition2) { // statements2 // ... } ... else if (conditionN) { // statementsN // ... } else { // statementsN+1 // ... }
here
- condition1, condition2, conditionN – conditional expressions. If the value of one of the conditional expressions is true, then the corresponding block of statements is executed. All other blocks (branches) of operators are skipped. For example, if condition2 = true, then only one block of statement2 is executed;
- statement1, statement2, statementN – one or more statements that are executed if the corresponding conditional expression is true. If after some if or else block you need to execute only one statement, then the curly braces { } are optional.
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5. Examples of using the if statement (short form)
5.1. The absolute value of a number
Task. Given a real number a, which is entered from the keyboard. Print its absolute value. Do not use additional functions in the program.
Solution.
fun main(args:Array<String>) { // Statement if(...) { ... } // 1. Variable declaration a val a : Double // 2. Input value of a print("a = ") a = readLine().toString().toDouble() // 3. Outputting the absolute value using // the shorthand form of the if statement if (a<0) println("abs(a) = " + (-a)) if (a>=0) println("abs(a) = " + a) }
The result of the program
a = -8 abs(a) = 8
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5.2. Calculating the sum of numbers
Task. Four real numbers are given. Find the sum of those numbers that are greater than 10. Do not use the loop operator.
Solution.
fun main(args:Array<String>) { // Statement if(...) { ... } // 1. Declaring variables val a : Double val b : Double val c : Double val d : Double var summ : Double = 0.0 // The required summ val Value : Double = 10.0 // number to compare // 2. Input numbers a, b, c, d print("a = "); a = readLine().toString().toDouble() print("b = "); b = readLine().toString().toDouble() print("c = "); c = readLine().toString().toDouble() print("d = "); d = readLine().toString().toDouble() // 3. Calculation using the if statement if (a>Value) summ += a if (b>Value) summ += b if (c>Value) summ += c if (d>Value) summ += d // 4. Print the result println("summ = " + summ) }
Program execution result
a = 15 b = 5 c = 6 d = 11 summ = 26.0
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6. Examples of using the if-else operator (full form)
6.1. Determining the sum of the digits of a number
A two-digit number is given. Determine if the sum of the digits of a number is a two-digit number. For example, for number 78, the sum of the digits is 15, which means the answer is “Yes”.
Solution.
fun main(args:Array<String>) { // Statement if-else // 1. Declaring variables val num : Int // Specified number // 2. Input number num print("num = ") num = readLine().toString().toInt() // 3. Calculation // 3.1. Checking if a number is two-digit if ((num<10) || (num>99)) { println("Incorrect input.") return } // 3.2. Calculate the sum of the digits of a number val sum = (num % 10 + num / 10) // 3.3. Print the result if (sum > 9) println("Yes") else println("No") }
Program execution result
num = 57 Yes
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6.2. Checking the fulfillment of inequality
Task. Three numbers a, b, c are given. Check if the inequality a<b<c holds.
Solution.
fun main(args:Array<String>) { // Statement if-else // 1. Declaring variables val a : Int val b : Int val c : Int // 2. Print the numbers a, b, c print("a = ") a = readLine().toString().toInt() print("b = ") b = readLine().toString().toInt() print("c = ") c = readLine().toString().toInt() // 3. Calculation and output of the result if ((a<b) && (a<c)) println("a<b<c => true") else println("a<b<c => false") }
Program execution result
a = 5 b = 9 c = 12 a<b<c => true
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7. Examples of using the operator if-else-if (ladder form)
7.1. Determining a shorter distance
Task. Two distances are known, one in kilometers and the other in feet (1 foot = 0.45 m). Which of the distances is shorter and which is longer? Work through all possible options.
Solution.
fun main(args:Array<String>) { // Statement if-else-if // 1. Declaring Variables val lenKm : Double // distance in kilometers val lenFt : Double // distance in feet (1 ft = 0.45 m) // 2. Input distance print("Distance in kilometers: lenKm = "); lenKm = readLine().toString().toDouble() print("Distance in feet: lenFt = "); lenFt = readLine().toString().toDouble() // 3. Calculation. The if-else-if statement is used if (lenKm*1000 > lenFt*0.45) // Bring all distances to meters println("lenKm > lenFt") else if (lenKm*1000 < lenFt*0.45) println("lenKm < lenFt") else println("lenKm == lenFt") }
Program execution result
Distance in kilometers: lenKm = 0.9 Distance in feet: lenFt = 2000 lenKm == lenFt
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7.2. Determining the quarter number on the coordinate plane
Task. Display the number of the quarter of the coordinate plane to which the point with coordinates (x, y) belongs, provided that x≠0 and y≠0.
fun main(args:Array<String>) { // Statement if-else-if // 1. Declaring variables val x : Double val y : Double // 2. Input values x, y print("x = ") x = readLine().toString().toDouble() print("y = ") y = readLine().toString().toDouble() // 3. Calculation and output the result if ((x==0.0) || (y==0.0)) { println("Incorrect input") return } if ((x>0) && (y>0)) println("1") else if ((x>0) && (y<0)) println("4") else if ((x<0) && (y>0)) println("2") else println("3") }
Program execution result
x = 5 y = -2 4
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Related topics
- Basic types. Numeric literals. Numeric constants. Examples
- Variables and constants. Keywords var, val, const
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