Meaning of ";" in PlotlyJS

General Usage
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1

I was always wondered what does “;” means in all examples.

The following functions give me the same output.

using PlotlyBase

function linescatter1()
    trace1 = scatter(;x=1:4, y=[10, 15, 13, 17], mode="markers")
    trace2 = scatter(;x=2:5, y=[16, 5, 11, 9], mode="lines")
    trace3 = scatter(;x=1:4, y=[12, 9, 15, 12], mode="lines+markers")
    Plot([trace1, trace2, trace3])
end

function linescatter2()
    trace1 = scatter(x=1:4, y=[10, 15, 13, 17], mode="markers")
    trace2 = scatter(x=2:5, y=[16, 5, 11, 9], mode="lines")
    trace3 = scatter(x=1:4, y=[12, 9, 15, 12], mode="lines+markers")
    Plot([trace1, trace2, trace3])
end
2

I think it’s just function syntax for keyword parameters: Functions · The Julia Language
example:

julia> function t(; x = 1, y = 2 )
       println(x,y)
       end

julia> t(x=4,y=5)
45

julia> t(;x=4,y=5)
45

You can omit the ;

When the function is called, the semicolon is optional

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3

I see. But why should I use it? In other words, why all examples are written with “;” in function calls?

4

Perhaps to make it clear that these are keyword parameter? I don’t know, why is this important?

5

You don’t need it for keyword arguments, but you do need it for splatting keyword arguments.

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6

I was just looking for a reason why to use it.

7

Oh and you also need it when defining functions with keyword arguments. And for these reasons some people just always add them so they don’t have to think about it

8

Here’s two other cases where you would need to use ;

If we define

kwargs = Dict(:x => 3, :y => 4)
foo(; x, y) = x + y # x and y are keyword arguments

Then you need to use

foo(; kwargs...) # equivalent to foo(; x=3, y=4)

Instead of

foo(kwargs...) # equivalent to foo(x => 3, y => 4)

Also with

bar = "baz"
foo(; bar) = println(bar)

Then you want

foo(; bar) # equivalent to foo(bar=bar)

Instead of

foo(bar)

Although these are fairly specific cases. In most cases you can just ignore the semicolon.

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