Programming Fundamentals Chapter 05 – Functions Part-B, Slides of Programming Languages

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Programming Fundamentals

Chapter 05 – Functions

Part-B

Functions

• Collection of Statements that perform

specific task

• Introduces Modular programming

• The breaking up of a program into a set of

manageable functions

Functions

• Defining/Calling Functions

• Function Call is a statement that causes a

function to execute

• Function Call will give a name and may

pass an argument

• So far, we see main() as a function … but

without any argument.

Functions

• Benefits

• Makes coding manageable
• Software re-usability (use existing blocks to

create new programs)

• Avoid repeating code in a program
• Saves time
• Reduces coding complexities

Functions

• Example: Math Library Functions
  • Perform common mathematical calculations
  • cout << sqrt( 900.0 );
    • Name
    • Open Parenthesis
    • Argument
    • Close Parenthesis
  • Math functions always take argument of type double and always returns result of type double
  • #include
  • Alternate → cout << sqrt (c1 + d * f );
    • i.e., arguments can be constants, variables, or even expressions

Functions

• Example: Math Library Functions
  • ceil(x) → rounds x to smallest integer not less than x
  • cos(x) → cosine of x
  • exp(x) → exponential function e x
  • floor(x) → rounds x to larger integer not greater than x
  • fmod(x,y) → remainder of x/y as float
  • log(x) → natural log of x
  • log10(x) → log of x (base 10)
  • pow(x,y) → x ^ y
  • sin(x) → sign of x
  • sqrt(x) → square root of x
  • tan(x) → Tangent of x

Moving Ahead

• So far we have seen Functions in two

forms:

• As the main() function (of every program)
• As a call to a library function (e.g., sqrt and

pow)

• Next Step → Creating our own functions

Function Usage (

st

Example)

Our User Defined Function = Square() Calculates Square of No.s from 1 to 10 integer values are passed to and forth Function square is invoked from within main() with call square(x) The actual call is the (). Don’t forget this.

• Actual Function Definition
• square receives value of x in parameter y
• If function is not returning anything to main(), then at least it should simply pass control back with return; Function Prototype Declaration int tells compiler that square returns integer void means nothing returned Omitting type would be syntax error

Function This Function That

• Function Prototype

• Function Signature

• Function Header

Function Prototype/Function

Declaration

• int square (int)
  • Right int informs compiler that square expects an integer value from caller
  • Left int informs compiler that square returns an integer result to caller
• Compiler checks:
  • Correct return type?
  • Correct number of arguments?
  • Correct argument types?
  • Correct order of arguments?
• Not required if function body appears BEFORE

first use in program

Function Signature

• Signature or Function Signature is the

portion of function prototype containing:

• Name of function
• Type of arguments Signature portion of the function prototype

Function Header

• The declaration preceding the actual

Function Block

Header Preceding the Function Body

General Format

Return-value-type function-name(parameter-list) { declaration and statements; }

• Function-name → Can be any valid identifier
• Return-value-type → data type of result returned from function to caller
• Parameter-list → comma separated. If no arguments passed, then will be left empty.
• Decl. & statements → Form the function body (or Block)

Return of Control

1 Caller Function 2