Crashed Julia with <

New to Julia
1

Hi,

I have defined the following two types:

struct Percentage <: Real
    value::Float64
    Percentage(x) = x < 0 ? new(0) : x > 1 ? new(1) : new(round(x, digits = 6))
end

Base.show(io::IO, x::Percentage) = print(io, "$(x.value * 100)%")

Base.convert(::Type{Percentage}, x::Real) = Percentage(x)
Base.convert(::Type{Percentage}, x::Percentage) = x

Base.promote_rule(::Type{T}, ::Type{Percentage}) where T <: Real = Percentage

import Base: +, -, <, >, <=, >=, ==

+(x::Percentage, y::Percentage) = Percentage(x.value + y.value)
-(x::Percentage) = Percentage(-x.value)
-(x::Percentage, y::Percentage) = Percentage(x.value - y.value)
<(x::Percentage, y::Percentage) = x.value < y.value
<=(x::Percentage, y::Percentage) = x.value <= y.value
>(x::Percentage, y::Percentage) = x.value > y.value
>=(x::Percentage, y::Percentage) = x.value >= y.value
==(x::Percentage, y::Percentage) = x.value == y.value

Base.max(x::Percentage, y::Percentage) = Percentage(max(x.value, y.value))
Base.min(x::Percentage, y::Percentage) = Percentage(min(x.value, y.value))

mutable struct Health <: Real
    current::Percentage
    Health(current=1) = new(current)
end

Base.convert(::Type{Health}, x::Real) = Health(x)
Base.convert(::Type{Health}, x::Health) = x

Base.promote_rule(::Type{T}, ::Type{Health}) where T <: Real = Health


import Base: +, -, <, >, <=, >=, ==

+(x::Health, y::Health) = Health(x.current + y.current)
-(x::Health) = Health(-x.current)
-(x::Health, y::Health) = Health(x.current - y.current)
<(x::Health, y::Health) = x.current < y.current
<=(x::Health, y::Health) = x.current <= y.current
>(x::Health, y::Health) = x.current > y.current
>=(x::Health, y::Health) = x.current >= y.current
==(x::Health, y::Health) = x.current == y.current

Base.max(x::Health, y::Health) = Health(max(x.current, y.current))
Base.min(x::Health, y::Health) = Health(min(x.current, y.current))

When I type

Health(0.1) < Percentage(0.2)

in the REPL, I get the message that Julia has exited.

Iā€™m using JuliaPro 1.5.2-2 on Mac OS X 10.15.7

Is there anyone who has an idea what is going on?

Thanks in advance,
Stef

2

You have specified that Health and Percentage take precedence over other Real types but have not specified which of them takes precedence. As both are subtypes of Real themselves, that triggers an error.

On Linux, I get stack overflow from promotions.

In short, you need promote_rule(::Type{Percentage}, ::Type{Health}).

3 Likes
3

Apparently I needed to reverse the order of the types to solve it.

promote_rule(::Type{Health}, ::Type{Percentage})