Hi Björn,
This is a bit brute force but it seems to work.
g=: i.~ f"0@:i.@:+:
g 87
75
Essentially applying f to a list up to twice the argument (y) and returning the
index (x) of the first spot f(x)=y
Cheers, bob
ps. I believe your original f can also be written as:
f1=: [: # i. -./ 2 3 ^~ i.
On 2010-12-26, at 11:47 AM, Björn Helgason wrote:
> I have a small task that looks like this
>
> f=: [: # i. -. (2 ^~ i.) , 3 ^~ i.
> f 87
> 75
>
> I want to use tacit to find what number gives me 75 numbers (the answer
> being 87)
>
> Could be asking what argument y do I need to find x numbers according to the
> formula above
>
> --
> Björn Helgason, Verkfræðingur
> Fornustekkum II
> 781 Hornafirði,
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>
>
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>
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