c-10

Lecture 10Lecture 10Version 1.0Version 1.0

More on FunctionsMore on Functions

Scope RulesScope Rules

Math Library FunctionsMath Library Functions

2Rushdi Shams, Dept of CSE, KUET, Bangladesh

More Knowledge on More Knowledge on FunctionsFunctions

Actual Arguments

Formal Arguments



Instead of using different variable Instead of using different variable names names xx, , y y and and zz, we could have , we could have used the same variable names used the same variable names aa, , b b and and cc

compiler would still treat them as compiler would still treat them as different variables since they are in different variables since they are in different functions different functions



There is no restriction on the number of There is no restriction on the number of return return statements that may be present in a statements that may be present in a function function

return return statement need not always be statement need not always be present at the end of the called function present at the end of the called function



All the following are valid All the following are valid return return statements statements In the last statement a garbage value is In the last statement a garbage value is

returned to the calling function since we are returned to the calling function since we are not returning any specific value not returning any specific value

Note that in this case the parentheses after Note that in this case the parentheses after return return are dropped are dropped



A function can return only one value at a A function can return only one value at a time time

the following statements are invalid the following statements are invalid



If the value of a formal argument is If the value of a formal argument is changed in the called function, the changed in the called function, the corresponding change does not take place corresponding change does not take place in the calling function in the calling function


Calling ConventionsCalling Conventions

Calling convention indicates the order in Calling convention indicates the order in which arguments are passed to a function which arguments are passed to a function when a function call is encountered when a function call is encountered

There are two possibilities here: There are two possibilities here:

1.1. Arguments might be passed from left to Arguments might be passed from left to right. right.

2.2. Arguments might be passed from right to Arguments might be passed from right to left. left.

C language follows the second order C language follows the second order



In this call it doesn’t matter whether the In this call it doesn’t matter whether the arguments are passed from left to right or from arguments are passed from left to right or from right to left right to left

However, in some function call the order of However, in some function call the order of passing arguments becomes an important passing arguments becomes an important consideration consideration


Scope RulesScope Rules

The scope of an identifier is the The scope of an identifier is the portion of the program in which an portion of the program in which an identifier is referenced identifier is referenced

When we declare a local variable in When we declare a local variable in a block, it can be referenced only in a block, it can be referenced only in that block or in blocks nested within that block or in blocks nested within that block that block



Math library functions allow the Math library functions allow the programmer to perform certain common programmer to perform certain common mathematical calculations mathematical calculations

A programmer desiring to calculate and A programmer desiring to calculate and print the square root of 900.0 can write-print the square root of 900.0 can write-



When the statement is executed, sqrt() is When the statement is executed, sqrt() is called to calculate the square root of the called to calculate the square root of the number contained in the parenthesis (900.0) number contained in the parenthesis (900.0)

The number 900.0 is the argument of sqrt() The number 900.0 is the argument of sqrt() function function

The statement will print 30.00 The statement will print 30.00 sqrt() function takes an argument of type sqrt() function takes an argument of type

double and returns a result of type double double and returns a result of type double All math library functions return the data All math library functions return the data

type double type double



If c1=13.0, d=3.0 and f=4.0, then the line If c1=13.0, d=3.0 and f=4.0, then the line would print 5.00 would print 5.00


Other Useful Math Other Useful Math FunctionsFunctions

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