Simpler Syntax For Conversion to integers

I am trying to find some simpler syntax for variable type converters. In my scripts, I have been declaring variables for controlling the behavior like this:

FFT_Size = 128

I may then use this variable to control loops, create arrays, etc. The problem is that the numbers are treated as floats and I need them to be integers. For example in C, if I assign a float to an int, it will auto truncate the value. In many cases I need to divide this control variable by an integer.

For example:

Data = Array{Complex64}(convert(UInt32,floor(FFT_Size/2)))

I would like to simple do something like this:

Data = Array{Complex64}(FFT_Size/2)

In this case I am simple trying initialize an array of complex numbers with a length of the FFT_Size. I am sure there is a much simpler way of achieving this.

It does not seem like globals can have a type assigned like this:


Lastly it seems if I doing something like this:

a = 128::Int

the expression

a/2 or a/2::Int

will always yield a Float64

I often have to create new arrays where the length is dependent on some prior computation. Maybe I am simply approaching this incorrectly?

Use div, which performs integer division. If you’re in the REPL or an editor with tab-completion, you can also use ÷ (typed as \div <tab>).

julia> 11 ÷ 4

julia> typeof(ans)

128 is an integer, and is treated as such. If you want a floating point number, you have to write 128.0. That’s not your problem. What is hitting you is that / does ‘floating point division’. It has to, otherwise 1/2 wouldn’t give you 0.5.

As @stillyslalom says, in order to keep the output as integers you have to explicitly ask for it, by using integer division, div.


The div function also produces an integer by rounding down. If FFT_Size happens to be odd I would venture that your Data array will be too short by 1.

Note that you can use a::Int = 128 to ensure that a stays as an integer. In this case if you do floating point division you might run into some InexactErrors. For example

julia> function div2(a)
       b::Int = a
       b = b/2
       return b
div2 (generic function with 1 method)

julia> div2(128)

julia> div2(129)
ERROR: InexactError: Int64(Int64, 64.5)
 [1] Type at ./float.jl:692 [inlined]
 [2] convert at ./number.jl:7 [inlined]
 [3] div2(::Int64) at ./REPL[10]:3
 [4] top-level scope at none:0
floor(Int, 9/2)
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