Dart Programming - Decision Making

 

Dart Programming - Decision Making 

A conditional/decision-making construct evaluates a condition before the instructions are executed.

Conditional constructs in Dart are classified in the following table.

Sr.No	Statement & Description
1	if statement An if statement consists of a Boolean expression followed by one or more statements.
2	If...Else Statement An if can be followed by an optional else block. The else block will execute if the Boolean expression tested by the if block evaluates to false.
3	else…if Ladder The else…if ladder is useful to test multiple conditions. Following is the syntax of the same.
4	switch…case Statement The switch statement evaluates an expression, matches the expression’s value to a case clause and executes the statements associated with that case.

Dart Programming - Numbers

Dart numbers can be classified as −

• int − Integer of arbitrary size. The int data type is used to represent whole numbers.

• double − 64-bit (double-precision) floating-point numbers, as specified by the IEEE 754 standard. The double data type is used to represent fractional numbers

The num type is inherited by the int and double types. The dart core library allows numerous operations on numeric values.

The syntax for declaring a number is as given below −

int var_name;      // declares an integer variable 
double var_name;   // declares a double variable 

Example

void main() {
   // declare an integer
   int num1 = 10;             
     
   // declare a double value
   double num2 = 10.50;  

   // print the values
   print(num1);
   print(num2);
}

It will produce the following output −

10 
10.5 

Note − The Dart VM will throw an exception if fractional values are assigned to integer variables.

Parsing

The parse() static function allows parsing a string containing numeric literal into a number. The following illustration demonstrates the same −

 Live Demo

void main() { 
   print(num.parse('12')); 
   print(num.parse('10.91')); 
}

The above code will result in the following output −

12 
10.91

The parse function throws a FormatException if it is passed any value other than numerals. The following code shows how to pass an alpha-numeric value to the parse() function.

Example

 Live Demo

void main() { 
   print(num.parse('12A')); 
   print(num.parse('AAAA')); 
}

The above code will result in the following output −

Unhandled exception: 
FormatException: 12A 
#0 num.parse (dart:core/num.dart:446) 
#1 main (file:///D:/Demos/numbers.dart:4:13) 
#2 _startIsolate.<anonymous closure> (dart:isolatepatch/isolate_patch.dart:261) 
#3 _RawReceivePortImpl._handleMessage (dart:isolatepatch/isolate_patch.dart:148)

Number Properties

The following table lists the properties supported by Dart numbers.

Sr.No	Property & Description
1	hashcode Returns a hash code for a numerical value.
2	isFinite True if the number is finite; otherwise, false.
3	isInfinite True if the number is positive infinity or negative infinity; otherwise, false.
4	isNan True if the number is the double Not-a-Number value; otherwise, false.
5	isNegative True if the number is negative; otherwise, false.
6	sign Returns minus one, zero or plus one depending on the sign and numerical value of the number.
7	isEven Returns true if the number is an even number.
8	isOdd Returns true if the number is an odd number.

Number Methods

Given below are a list of commonly used methods supported by numbers −

Sr.No	Method & Description
1	abs Returns the absolute value of the number.
2	ceil Returns the least integer no smaller than the number.
3	compareTo Compares this to other number.
4	Floor Returns the greatest integer not greater than the current number.
5	remainder Returns the truncated remainder after dividing the two numbers.
6	Round Returns the integer closest to the current numbers.
7	toDouble Returns the double equivalent of the number.
8	toInt Returns the integer equivalent of the number.
9	toString Returns the string equivalent representation of the number.
10	truncate Returns an integer after discarding any fractional digits.