Lesson 26 of 55
9 mins readImmutable Composite Types (struct)
In Plain English
In Julia, structs are immutable by default. Immutable structs are stack-allocated with zero garbage collection overhead and inline memory layout.
Deep Dive: How It Works
Struct Syntax: struct Point2D x::Float64; y::Float64 end.
Field Access: Accessed via dot notation: pt.x, pt.y.
Immutability: Attempting to assign pt.x = 10.0 throws an error. Immutability allows the compiler to optimize data structures into pure CPU registers.
Core Rules to Remember
Immutable by Default: Enables extreme compiler optimizations and thread-safe data access.
Type-Annotated Fields: Always annotate fields with concrete types (e.g. x::Float64) for maximum speed.
Live Interactive Example
Hit Run Code to see it liveImmutable Struct and Geometric Calculations
Python 3.12
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Output Console
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How it works: Point is stack-allocated; distance evaluates with pure hardware registers.
Your Turn: Micro Challenge
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Micro Exercise
Define Rectangle Struct
- Define `struct Rectangle width::Float64; height::Float64 end`.
- Define `area(r::Rectangle) = r.width * r.height`.
- Create `rect = Rectangle(4.0, 5.0)` and print `"Area: $(area(rect))"`.
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Sandbox Output
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