# [OpenSCAD] Openscad Indirect Functions

doug moen doug at moens.org
Thu Oct 20 12:08:53 EDT 2016

```In my high school algebra text book, the → is used exactly as I have
described. Here's a quote from an exercise:

In f : x → x², x ∈ R, what is the image of 2?

Citation:
http://www.mathhelp.com/how_to/functions/function_and_arrow_notation/

The → is *also* used when describing the domain and range of a function, eg
f : R→R.

Citation: http://mathworld.wolfram.com/Function.html

So I think → notation for functions is common and well understood in high
school classrooms.

On 19 October 2016 at 09:44, Lucas Vinicius Hartmann <
lucas.hartmann at gmail.com> wrote:

> 2016-10-18 17:51 GMT-03:00 doug moen <doug at moens.org>:
>
>> The → symbol is what's used in mathematics to describe functions, eg f :
>> x → x².
>>
>
> I am not really sure, but If I remember correctly the usage of the arrow
> in math is not exactly that. It describes a property of the function, not
> the function itself.
>
> The arrow is used pointing to a SET that contains all possible answers for
> the function, but does not specify what is the answer for a partigular
> input. Basically it is equivalent to the return type of a function
> prototype in C/C++.
>
> If, for instance, we have a cubic function given by
>
> f(x) = x*x*x
>
> Then f(x) may return any real number, so the result set is all real
> numbers.
>
> f(x) -> R     (Imagine the stylish R for real numbers here)
>
> If f2(x) was a square function, then only positive real numbers could be
> returned, so...
>
> f2(x) -> R+
>
> That said, the usage of arrows in openscad or programming languages is up
> to the developers. :-)
>
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