Julia Language Functions Anonymous functions
Example
Arrow syntax
Anonymous functions can be created using the -> syntax. This is useful for passing functions to higher-order functions, such as the map function. The below function computes the square of each number in an array A.
squareall(A) = map(x -> x ^ 2, A)
An example of using this function:
julia> squareall(1:10)
10-element Array{Int64,1}:
1
4
9
16
25
36
49
64
81
100
Multiline syntax
Multiline anonymous functions can be created using function syntax. For instance, the following example computes the factorials of the first n numbers, but using an anonymous function instead of the built in factorial.
julia> map(function (n)
product = one(n)
for i in 1:n
product *= i
end
product
end, 1:10)
10-element Array{Int64,1}:
1
2
6
24
120
720
5040
40320
362880
3628800
Do block syntax
Because it is so common to pass an anonymous function as the first argument to a function, there is a do block syntax. The syntax
map(A) do x
x ^ 2
end
is equivalent to
map(x -> x ^ 2, A)
but the former can be more clear in many situations, especially if a lot of computation is being done in the anonymous function. do block syntax is especially useful for file input and output for resource management reasons.
