Julia: keyword arguments to a function

Some times a function can be defined with more arguments, in that case it is very difficult to remember the order of arguments. Julia provides a facility that you can refer arguments by name. Semicolon is used in signature of the function to differentiate keyword arguments.

function processData(x,y;longitude=10.0,latitude=20.0, color="Black")

All the arguments after semi colon are keyword arguments, these can be referred by name.

You can call above function in following ways.

processData(10,20)

processData(10,20,color="Red")

processData(10,20,color="Red", latitude=123.4466)

julia> function processData(x,y;longitude=10.0,latitude=20.0, color="Black")
           println("x=$x")
           println("y=$y")
           println("longitude=$longitude")
           println("latitude=$latitude")
           println("color=$color")
       end
processData (generic function with 1 method)

julia> processData(10,20)
x=10
y=20
longitude=10.0
latitude=20.0
color=Black

julia> processData(10,20,color="Red")
x=10
y=20
longitude=10.0
latitude=20.0
color=Red

julia> processData(10,20,color="Red", latitude=123.4466)
x=10
y=20
longitude=10.0
latitude=123.4466
color=Red

Keyword arguments and varargs

By using varargs (…), you can collect extra keyword arguments.

function processData(x,y;color="Black", args...)

All the extra keyword arguments are collected in the argument args, args will be a collection of (key,value) tuples.

julia> function processData(x,y;color="Black", args...)
           println("x=$x")
           println("y=$y")
           println("color=$color")

           for i in args
               println(i)
           end
       end
processData (generic function with 1 method)

julia> processData(10,20,color="Red", latitude=123.4466)
x=10
y=20
color=Red
(:latitude,123.4466)

julia> processData(10,20,color="Red", latitude=123.4466, name="Krishna", area="Bangalore")
x=10
y=20
color=Red
(:latitude,123.4466)
(:name,"Krishna")
(:area,"Bangalore")

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