Programming Language Syntax and semantics

UNIT I

BB yy

Kainjan Sanghavi

Contents

• Routines

• Generic Routines

• Aliasing and Overloading

• Parameter Passing Methods

Routines

In programming language routines come

into two forms :

1. Procedures : does not return a value

2. Functions : Return a value

Assembly language

• Subprograms

FORTRAN

• Subroutines

Pascal

• Procedures

Ada , C

• Functions

Routines Routines are called as : follows depending upon the programming language :

Routines Routines have

1. Name : Routine declaration

2. Scope : From starting of function till closing

3. Type : Routines header defines its routine

type…….i.e method signature

4. L-value : Reference to the memory area which

stores the routines executable statements

int (*ps)(int) ; ps = ∑

1. R-value : Executable statements : int i = (*ps)(5);

Generic Routines means templates

Refer :

https://kainjan1.wordpress.com/oop-course-file/oop-

notes/

Lec37 : 16-8-2016FunctionTemplates Lec38 : 19-8-2016ClassTemplates Lec39:20-8-2016OverloadingTemplates

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Aliasing

• In computing, aliasing describes a situation in which a data location in memory can be accessed through different symbolic names in the program.

• Thus, modifying the data through one name implicitly

modifies the values associated with all aliased names, which may not be expected by the programmer.

Aliasing

• As a result, aliasing makes it particularly difficult to

understand, analyze and optimize programs.

• Aliasing analyzers intend to make and compute

useful information for understanding aliasing in

programs.

Overloading

Refer : https://kainjan1.wordpress.com/oop-course-file/oop-notes/ Lec16:9-7-2016Function Overloading Lec 17,18 :12-7-2016: UNIT II OperatorOverloading

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Parameter Passing

Methods 1. call by value : copy going into the procedure 2. call by result : copy going out of the procedure 3. call by value-result : copy going in, and again

going out 4. call by reference : pass a pointer to the actual

parameter, and indirect through the pointer 5. call by name : re-evaluate the actual parameter on every use.

For actual parameters that are simple variables, this is the same as call by reference. For actual parameters that are expressions, the expression is re-evaluated on each access

Parameter Passing

Methods

• Fortran uses call by reference

• Algol 60 has call by name, call by value

• Lisp and Smalltalk use call-by-value with

pointer semantics.

• Java uses call-by-value

Example 1: illustrates call by

value, value-result, reference

begin integer n; procedure p(k: integer); begin n := n+1; k := k+4; print(n); end; n := 0; p(n); print(n); end;

Note that when using call by reference, n and k are aliased. Output: call by value: 1 1 call by value-result: 1 4 call by reference: 5 5

Example 2: Call by value and

call by name

begin integer n; procedure p(k: integer); begin print(k); n := n+1; print(k); end; n := 0; p(n+10); end;

Output: call by value: 10 10 call by name: 10 11

Example 3: Call by value and call by

name (with evaluation errors)

begin integer n; procedure p(k: integer); begin print(n); end; n := 5; p(n/0); end;

Output: call by value: divide by zero error call by name: 5

Thank You!

Angelin