Functions, Subroutines, Calling Sequence

Functions, Subroutines, Calling Sequence

Perform computations and return a value.

Functions

Execute a series of instructions but do not return a value.

Subroutines

Advantages of Functions and Subroutines

• Modularity

• Reusability

• Easier debugging

• Readability

FUNCTION or SUBROUTINE?

Calculate the square of a number.

FUNCTION

FUNCTION or SUBROUTINE?

Displaying messages

SUBROUTINE

Anatomy of a Function

• Parameters

• body

• return statement

Types of functions

• Void

• Value-returning

Scope and Lifetime of Functiosn

• Local

• Global

• Static

Return Values of Functions

• Single

• Multiple

Standalone blocks of reusable code.

Subroutines

Simplifying complex logic by splitting tasks into subroutines.

Procedural Abstraction

When to Use Subroutines?

• For repetitive tasks (e.g., input/output operations).

• To increase maintainability and clarity.

Subroutines and Procedural Abstraction Examples

• Subroutine for data validation.

• Recursive subroutines for algorithms like factorial or Fibonacci.

Defining functions inside other functions.

Nested Functions/Subroutines

Two cases inside when performing recursive call

• Base Case

• Recursive Case

Functions that take other functions as parameters or return them

Higher Order Functions

Examples of Higher-Order Functions

• Map

• Filter

• Reduce

Reducing overhead with inline functions or efficient recursion.

Optimization

Best Practices for Functions and Subroutines

• Naming conventions

• Modular design principles

• Avoiding side effects

The set of actions taken by a program to transfer control to a subroutine and back.

Calling sequence

Calling sequence includes managing?

• Function arguments

• return values

• call stack

Steps in a Calling Sequence:

Caller Responsibilities

• Save necessary registers and program state.

• Push arguments onto the stack or into registers.

• Jump to the function's address.

Steps in a Calling Sequence:

Callee Responsibilities

• Allocate space for local variables.

• Execute the function body.

• Store the return value.

• Restore the caller's state and return control.

Specifies how arguments are passed, return values are handled, and the stack is managed.

Calling Conventions

Common conventions for Calling Sequence

• CDECL

• STDCALL

• FASTCALL

Caller cleans up the stack.

CDECL

Callee cleans up the stack.

STDCALL

Uses registers for argument passing.

FASTCALL

are variables that act as placeholders for the input data a function or method needs to operate.

Parameters

They allow a function to receive and process information dynamically, making it reusable and versatile.

Parameters

Types of Parameters

• Formal Parameters

• Actual Parameters

These are defined in the function's declaration or definition.

Formal Parameters

They specify the input that the function expects when it is called.

Formal Parameters

These are the actual values or data passed to the function when it is called.

Actual Parameters/Arguments

Kinds of Parameters

• Positional Parameters

• Default Parameters

• Keyword Parameters

• Variable-Length Parameters

Arguments are matched to parameters based on their position in the function call.

Positional Parameters

Parameters with default values that are used if no argument is provided for them.

Default Parameters

Arguments are matched to parameters by name, regardless of their position.

Keyword Parameters

Functions can accept a variable number of arguments using special syntax.

Variable-Length Parameters

Functions can accept a variable number of arguments using special syntax. What are these?

• *args for positional arguments

• **kwargs for keyword arguments

Functions can accept a variable number of arguments using special syntax for positional arguments?

*args

Functions can accept a variable number of arguments using special syntax for keyword arguments?

**kwargs

Importance of Parameters

• Reusability

• Modularity

• Flexibility

Parameter Passing Mechanisms

• Pass by Value

• Pass by Reference

• Pass by Pointer

• Pass by Name

A copy of the argument is passed.

Pass by Value

A reference to the argument is passed.

Pass by Reference

When using this passing mechanism, modifying the parameter does not affect the original value.

Pass by Value

When using this passing mechanism, changes to the parameter reflect in the original variable.

Pass by Reference

A pointer to the memory address of the argument is passed.

Pass by Pointer

Expressions are re-evaluated each time they are accessed.

Pass by Name

Which of these is least commonly used?

• Pass by Value

• Pass by Reference

• Pass by Pointer

• Pass by Name

Pass by Name

Mechanism for writing generic, reusable code.

Templates

Useful for functions and classes that operate on different data types.

Templates

Types of Templates

• Function Templates

• Class Templates

Define functions with generic types.

Function Templates

Define classes with generic types.

Class Templates

What language is this?

Generic programming using type hints (typing).

Python

What language is this?

Generics with for collections (ArrayList).

Java

What language is this?

template T add(T a, T b) { return a + b;}

C++

Advantages of Templates

• Type safety and reusability.

• Reducing code duplication.

refers to the practice of writing programs that can manipulate, generate, or analyze other programs (or themselves) as their data. It enables developers to create highly dynamic and adaptable systems.

Metaprogramming

Programs can inspect and modify their own structure and behavior during runtime.

Reflection

Code can be treated as data structures that can be manipulated programmatically.

Code as Data

In Lisp, code is written in the same form as data structures, making it easy to manipulate. What concept is portrayed here?

Code as Data

Using reflection APIs in Java to dynamically call methods or change fields. What concept is portrayed here?

Reflection

Programs can write or modify other programs, often at compile time or runtime.

Code Generation

Using templates in C++ or macros in Lisp to generate boilerplate code. What concept is portrayed here?

Code Generation

A feature of many languages (e.g., Lisp, Rust) that allows compile-time code transformations.

Macros

Programs can execute code constructed as strings or data structures during runtime.

Dynamic Evaluation

Types of Metaprogramming

• Compile-Time Metaprogramming

• Runtime Metaprogramming

Code manipulation occurs during compilation.

Compile-Time Metaprogramming

Compile-Time Metaprogramming Tools

• C++ Templates

• Rust Macros

• MetaOCaml

Benefits of Compile-Time Metaprogramming

Performance improvements by resolving computations at compile time.

Code changes or decisions happen while the program is running.

Runtime Metaprogramming

Runtime Metaprogramming Tools

• Python decorators

• Java reflection.

Benefits of Runtime Metaprogramming

Greater flexibility and adaptability.

Advantages of Metaprogramming

• Code Reusability

• Flexibility

• Abstraction

  • Efficiency

Challenges of Metaprogramming

• Complexity

• Performance Overhead

• Maintainability

Applications of Metaprogramming

• Domain-Specific Languages (DSLs)

• Dynamic Frameworks

• Code Generation Tools

• Aspect-Oriented Programmign (AOP)

Python:

Reflection:

Dynamic Code Execution:

Metaclasses:

• Reflection: getattr() and setattr().

• Dynamic Code Execution: eval() and exec().

• Metaclasses: Customizing class creation.

JavaScript:

Dynamic Property Access:

Code Generation:

• Dynamic Property Access: Object.defineProperty.

• Code Generation: Use of eval for runtime code evaluation.

C++

Metaprogramming:

Templates for compile-time metaprogramming.

Example: Standard Template Library (STL) heavily uses metaprogramming techniques.

Macros to manipulate code as data, offering unparalleled flexibility. What language is this?

Lisp

Open classes and metaprogramming-friendly syntax. What language is this ?

Rust

In Rust, we can dynamically defining methods using ?

define_method

It is a set of statements that take inputs, do some specific computation and produces output.

Function

•A C++ function definition consists of a?

• function return type

• function name

• parameters

• function body

A C++ function consist of two parts:

• Declaration

• Definition

the function's name, return type, and parameters (if any)

Declaration

the body of the function (code to be executed)

Definition

It act as variables inside the function

Parameters

When a parameter is passed to the function, it is called an?

 argument.