Expressions

1
Expressions
2
Expressions

• A sequence of operands and operators that reduces
  to a single value.
• e.g. 5 3 (reduces to 8)
• Operator a syntactical token of the language
  that requires some action (mathematical, logical,
  bitwise, etc.).
• Operand Receives an operators action. May be
  one, two, or more operands in an expression.

3
Expressions

• Formats
• Primary identifier, constant, or parenthetical
  expression.
• Postfix expression/ operator
• Unary operator/ expression.
• Binary expression/ operator/ expression
• Ternary binary expression/ operator/ expression/
  operator/ expression
• Assignment variable/ operator/ expression

4
Expressions

• Primary
• a b12 name SIZE
• 5 3.14 a Hello
• (2 3 10) (a 5 b)
• Binary
• 5 3 a b a 5
• Assignment
• a 5

5
Cs Primary Math Operators

• Definitions
• Overloaded operator an operator that can perform
  more than one operation.
• Unary operator an operator that acts on one
  operand.
• Binary operator an operator that acts on two
  operands.

6
Cs Primary Math Operators

• Unary specifies positive amount
• Binary addition
• - Unary specifies negative amount
• Binary subtraction
• Multiplication
• / Division
• Modulus (remainder)

7
Cs Primary Math Operators

• Unary /-
• May be placed in front of single numeric
  literals, constants, or variables.
• age39 percentLoss-6.5
• scoretotal-numWrong
• define TEMP(10)
• num-TEMP

8
Cs Primary Math Operators

• Unary /-
• Always put a space between two s or two s
  when using as math operators.
• If is omitted C assumes the number is positive.
• int a
• int b5
• int c2
• a-(bc) /a gets -10/

9
Cs Primary Math Operators

• Division
• Use forward slash for division /.
• Performs integer division when both operands are
  integers.
• Performs floating-point division when at least
  one operand is non-integer.
• int score180
• int score295
• float avg
• avg(score1score2)/2 //What is stored in avg?

10
Cs Primary Math Operators

• Modulus
• is the modulus operator.
• Returns the remainder of a division
• Works with integers only.
• int remain
• remain102 //remain holds 0
• remain92 //remain holds 1

11
Cs Primary Math Operators

• Operator precedence
• Hierarchical structure of operators.
• Determines the order of operations performed.
• Operators of equal precedence calculated left to
  right.
• Highest Unary -
• /
• -
• Lowest

12
Cs Primary Math Operators

• Operator precedence
• Operators of highest precedence are calculated
  first.
• ans673 //ans gets 27
• Operators of equal precedence are calculated left
  to right (usually).
• ans34/6 //ans gets 2
• ans4/63 //ans gets 0

13
Cs Primary Math Operators

• Parenthesis
• Used to override precedence and make your code
  easier to read.
• ans(67)3 //ans gets 39
• You may want to split lengthy expressions into
  multiple lines of code to make it easier to
  understand.

14
Cs Primary Math Operators

• Multiple assignments
• Math operators are left associative (left to
  right).
• The equals assignment operator is right
  associative.
• num1num2num30

15
Cs Math Operators

• Compound operators ( - /
• --)
• Lower precedence than operators previously
  discussed.
• Shortens your statements.
• No advantage in efficiency.
• scorescore2
• priceprice0.75
• countcount1
• score2
• price0.75
• count

16
Type Conversion

• Implicit Type Conversion
• C will automatically convert any intermediate
  values to the proper type so that the expression
  can be evaluated.
• In all expressions (except assignments) any
  implicit type conversions will always be made to
  the more general type according to the following
  promotion order
• Promotion Hierarchy
• char?short ? int ? uint ? long ? ulong ? float ?
  double ? long double

17
Type Conversion

• Implicit Type Conversion

18

• include ltstdio.hgt
• int main(void)
• int x12
• int y5
• float c0
• ccx/y //right side implicitly cast as float
• printf("f",c) //outputs 2.000000
• return 0

19
Type Conversion

• Explicit Type Conversion
• Instead of letting the compiler implicitly
  convert your data, you can do it yourself using a
  cast expression operator.
• (float) a //must use parentheses
• (float) (ab) //operand must be unary expression.
• (float) a/b //explicit and implicit conversion.

20
Type Conversion

• include ltstdio.hgt
• int main(void)
• int x12
• int y5
• float c0
• cc(float)x/y //right side explicitly cast as
  float
• printf("f",c) //outputs 2.400000
• return 0

21

• /
  
• File rad_degree.c
• Author Duane Birnbaum
• Project Sample C Program
• Description This program converts radians to
  degrees.
• 
  /
• include ltstdio.hgt
• define PI 3.14159
• define FACTOR 180.0/PI
• int main(void)
• int radians
• float degrees
• printf("Enter the angle in radians ")
• scanf("d",radians)
• degreesradiansFACTOR //Will this work
  properly?