Re: [Haskell-beginners] How to convert a float or double number into a string?

In fact, I am not looking for some way to convert a float 0.75 to 3%4. Your reply is helpful! What I need is just as much number of digits as possible. If I can hold as many digits of pi, i.e. 3.1415926535... as possible and save it in a String, it will be perfect! Yi On Wed, Sep 18, 2013 at 9:00 PM, Oscar Benjamin wrote:

On 18 September 2013 13:48, yi lu wrote:

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If I use `show`, show 123.45, it will return "123.45", a desired answer.

However, for show 123.45678901234567890, it will return "123.45678901234568".

I want to save all digits into a string. I suppose I use a wrong type of number, which is Float.

Yes, it is the wrong type of number. Float can only store finitely many digits and you're asking for slightly too many. Also even if it *looks like* float has enough digits for your number in fact it has converted them from decimal to binary. For non-integers exact decimal to binary conversion is rarely possible. In this case the nearest binary float is 123.4567890123456805895330035127699375152587890625 but many of these decimal digits will be truncated from display.

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But what can I do to work right?

Are rational numbers acceptable in your problem?

http://stackoverflow.com/questions/7056791/how-to-parse-a-decimal-fraction-i...

Oscar _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners