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Declaring and Instantiating Custom Structures on the Fly in Various Programming Languages

Declaring and Instantiating Custom Structures on the Fly in Various Programming Languages

February 20, 2025 Digital

Declaring and Instantiating Custom Structures on the Fly in Various Programming Languages

When working with data in programming, it is often necessary to define and instantiate custom data structures. This can be done in various ways depending on the programming language being used. In this article, we will explore how to declare and instantiate a structure on the fly in several popular programming languages, including C, C , Python, JavaScript, and Go, each with its unique approach.

Introduction to Structs

A struct is a composite data type that allows you to group together different data types under a single name. Defining and instancing a struct can be done in a single step, which is particularly useful when creating temporary data structures or when prototyping new components.

C and C : Named and Anonymous Structs

Both C and C provide direct support for struct definitions. You can define a struct and create an instance of it on the fly, as shown in the following example in C:

include stdio.h
int main() {
    struct {
        int x;
        float y;
    } point;
    point.x  10;
    point.y  20.5;
    printf("%d %f
", point.x, point.y);
    return 0;
}

In C , the same functionality can be achieved using the struct keyword:

include iostream
int main() {
    struct {
        int x;
        float y;
    } point;
    point.x  10;
    point.y  20.5;
    std::cout

Python: NamedTuples and Classes

Python offers a more flexible approach with the namedtuple from the collections module and the use of classes. Here, we can define a Point using namedtuple:

from collections import namedtuple
Point  namedtuple('Point', ['x', 'y'])
point  Point(x10, y20.5)
print(f'Point: x{point.x}, y{point.y}')

Alternatively, you can use a simple class to define a similar structure:

class Point:
    def __init__(self, x, y):
        self.x  x
        self.y  y
point  Point(x10, y20.5)
print(f'Point: x{point.x}, y{point.y}')

JavaScript: Object Literals

JavaScript uses object literals for similar purposes. Here’s how to create a Point using an object literal:

const point  {
    x: 10,
    y: 20.5
}
console.log(`Point: {point.x} {point.y}`);

Go: On-the-Fly Struct Instantiation

Go also allows for the definition and instantiation of structs on the fly, similar to C and C :

package main
import "fmt"
func main() {
    point : struct {
        x int
        y float64
    }{x: 10, y: 20.5}
    ("Point: x%d y%f
", point.x, point.y)
}

Summary

The ability to declare a struct on the fly varies by language but the general idea is to define the structure and create an instance in a single step. This approach is particularly useful when you need to create lightweight, temporary data structures.

For specific programming languages, you can use named structs, anonymous structs, namedtuples, classes, or object literals. Each method has its own advantages and trade-offs, and the choice depends on the project requirements and the flexibility needed.

Keywords: structural definition, on-the-fly struct, custom struct declaration

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