On Thursday, 25 May 2017 23:44:58 UTC+10, David K. Storrs wrote:
> This isn't smooth, but it works:
>
> #lang at-exp racket
> (first (regexp-match @pregexp{\d+\.\d{0,4}} "15.123456789"))
> (first (regexp-match @pregexp{\d+\.\d{0,4}} "15.12"))
>
Thank you - that is certainly more complicated than I though it would be.
Another way would be to create a new real number, something like
(exact->inexact (bigfloat->real x))
and then apply the conversion to and from a string to it. For example:
> (require math/bigfloat)
> (bf-precision 255)
> (define x (bfsqrt (bf 3)))
> x
(bf
#e1.73205080756887729352744634150587236694280525381038062805580697945193301690881)
> (displayln (string->number (real->decimal-string (exact->inexact
> (bigfloat->real x)) 4 )))
1.732
I was just hoping there might be something neater!
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