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Type ConversionPrecedence & Associativity
- Aakash Singh
C
Learners
Type Conversion
What is Type Conversion?
• Type Casting or Type Conversion is a way to convert a variable from one data type to another data type.
• For example, if you want to store a long value into a simple integer then you can type cast long to int.
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Type Conversion
Types of Type Conversion
• There are two types of type conversion –
1. Implicit Type Conversion
2. Explicit Type Conversion
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1. Implicit Type Conversion
What is Implicit Type Conversion?
• C automatically converts any intermediate values to the proper type so that the expression can be evaluated without losing any significance.
• This automatic conversion is known implicit type
conversion.
• If the operands are of different types, the ‘lower type’ is automatically converted to the ‘higher’ type before the operation proceeds.
• The result is of the higher type.
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Implicit Type Conversion
short char
int
Unsigned int
long int
Unsigned long int
float
double
long double
Conversion
Hierarchy
C uses rule that, in all expressions except assignments, any implicit type conversions are made from a lower size to a higher size type as shown below.
This hierarchy
can be used
while evaluating
expressions.
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Example of Implicit Type Conversion
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Example of Implicit Type Conversion
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1. Explicit Type Conversion
What is Explicit Type Conversion?
• The type conversion performed by the programmer by posing the data type of the expression of specific type is known as explicit type conversion.
• The general form of a cast is :
(type-name) expression
• Here, ‘type-name’ is one of the standard C data types and the expression may be a constant, variable, or an expression.
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Use of Explicit Type Casting
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Example Action
X=(int)7.57.5 is converted to integer by truncation.
a = (int)21.3/(int)4.5Evaluated as (21/4) and the result would be 5.
b = (double)sum/n Division is done in floating point mode.
y = (int)(a+b)The result of (a+b) is converted to integer.
z = (int)a+ba is converted to integer and then added to b.
p = cos((double)x) Converts x to double before using it.
Example of Explicit Type Conversion
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Example of Explicit Type Conversion
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Precedence & Associativity
What is Precedence?• C has a precedence associated with it. This
precedence is used to determine how an expression involving more than one operator is evaluated.
What is Associativity?• The operators at higher level of precedence are
evaluated first.
• The operators of the same precedence are evaluated either from ‘left to right’ or from ‘right to left’ depending on the level. This is known as the associativity property of an operator.
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Precedence & Associativity
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Precedence rules decides the order in which different operators are applied.
Associativity rule decides the order in which multiple occurrences of the same level operator are applied.
C Operators with their Precedence & Associativity are listed in the following table.
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Operator Description Associativity Rank
()[]
Function callArray element reference
Left to right 1
+-++--!~*&sizeof(type)
Unary plusUnary minusIncrementDecrementLogical NegationOnes complementPointer referenceAddressSize of an objectType cast
Right to left 2
*/%
MultiplicationDivisionModulus
Left to right 3
+-
AdditionSubtraction
Left to right 4
<<>>
Left shiftRight shift
Left to right 5
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Operator Description Associativity Rank
<<=>>=
Less thanLess than or equal toGreater thanGreater than or equal to
Left to right 6
==!=
EqualityInequality
Left to right 7
& Bitwise AND Left to right 8
^ Bitwise XOR Left to right 9
| Bitwise OR Left to right 10
&& Logical AND Left to right 11
|| Logical OR Left to right 12
?: Conditional expression Right to left 13
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Operator Description Associativity Rank
=*= /= %=+= -= &=^= |=<<= >>=
Assignment operators
Right to left 14
, Comma operator Left to right 15
Summary of operator precedence
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‘Comma’ operator has lowest precedence.
‘Unary Operators’ are operators having highest precedence.
Operators sharing common block in the above table have equal priority or precedence.
While solving expression, equal priority operators are handled on the basis of FIFO [First in First Out]i.e., Operator Coming First is handled First.
Example of Precedence
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Example of Associativity
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