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### D.14.8 `mpfr` conversion functions

The functions described in this section convert between `mpfr` numbers and character strings, naturals, or standard IEEE floating point format (in their list representations). Where these functions have similar or equivalent counterparts in the `mpfr` library’s native API, the names have been changed for mnemonic reasons.

`dbl2mp`

  The input is a standard floating point number as in `math`. The result is an `mpfr` number equal to the input with a fixed precision, currently set to 160 bits.

`mp2dbl`

  The input is an `mpfr` number, and the output is the best possible approximation to it by a standard a double precision number.

`str2mp`

  The input is a pair `(prec,s)`, where prec is a natural number specifying the precision, and s is a string expressing a floating point number in C format. The output is an `mpfr` number with the specified precision.

`mp2str`

  The input is an `mpfr` number, and the output is a character string expressing the number in exponential decimal notation. Sufficiently many decimal digits are included in the string to express the full precision.

`nat2mp`

  The input is a natural number represented as described in Representation of Numeric and Textual Data, and the output is an `mpfr` number of sufficient precision to express the natural number exactly.

The `mp2str` function enhances the native `mpfr_get_str` function by properly formatting the output string rather than only listing the digits of the mantissa.

The `nat2mp` function does not rely on the `mpfr` native integer conversion functions, so natural numbers with any number of bits up to `MP_PREC_MAX` can be used losslessly. There is currently no conversion in the other direction.

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