Lesson 30 of 55
9 mins readType Conversions & Promotion Rules
In Plain English
Julia conversion and promotion system automatically elevates mixed types (e.g. Int32 + Float64 -> Float64) to a common precision type without loss of mathematical precision.
Deep Dive: How It Works
Explicit Conversion: convert(Float64, 42) converts integer 42 to 42.0.
Promotion System: promote(1, 2.5) returns (1.0, 2.5) by determining the common supertype/precision.
Custom Rules: Define Base.promote_rule(::Type{MyType}, ::Type{Float64}) to integrate custom types with standard mathematical operators.
Core Rules to Remember
convert(): Convert a value of one type to another explicitly.
promote(): Elevate multiple mixed-type arguments to a shared common type.
Live Interactive Example
Hit Run Code to see it liveConversions and Promotion Examples
Python 3.12
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Output Console
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How it works: 10 was promoted to Float64 so both values share the same concrete type.
Your Turn: Micro Challenge
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Micro Exercise
Parse and Convert String to Float
- Parse `"99.95"` into a `Float64` using `parse(Float64, "99.95")`.
- Print `"Parsed price: $price"`.
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Sandbox Output
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