Changed Functions (GNU MPFR 4.2.1)
Description: How to install and use GNU MPFR, a library for reliable multiple precision floating-point arithmetic, version 4.2.1.

### 6.3 Changed Functions

The following functions and function-like macros have changed after MPFR 2.2. Changes can affect the behavior of code written for some MPFR version when built and run against another MPFR version (older or newer), as described below.

- The formatted output functions (`mpfr_printf`, etc.) have slightly changed in MPFR 4.1 in the case where the precision field is empty: trailing zeros were not output with the conversion specifier ‘`e`’ / ‘`E`’ (the chosen precision was not fully specified and it depended on the input value), and also on the value zero with the conversion specifiers ‘`f`’ / ‘`F`’ / ‘`g`’ / ‘`G`’ (this could partly be regarded as a bug); they are now kept in a way similar to the formatted output functions from C. Moreover, the case where the precision consists only of a period has been fixed in MPFR 4.2 to be like ‘`.0`’ as specified in the ISO C standard (it previously behaved as a missing precision).
- `mpfr_abs`, `mpfr_neg` and `mpfr_set` changed in MPFR 4.0. In previous MPFR versions, the sign bit of a NaN was unspecified; however, in practice, it was set as now specified except for `mpfr_neg` with a reused argument: `mpfr_neg(x,x,rnd)`.
- `mpfr_check_range` changed in MPFR 2.3.2 and MPFR 2.4. If the value is an inexact infinity, the overflow flag is now set (in case it was lost), while it was previously left unchanged. This is really what is expected in practice (and what the MPFR code was expecting), so that the previous behavior was regarded as a bug. Hence the change in MPFR 2.3.2.
- `mpfr_eint` changed in MPFR 4.0. This function now returns the value of the E1/eint1 function for negative argument (before MPFR 4.0, it was returning NaN).
- `mpfr_get_f` changed in MPFR 3.0. This function was returning zero, except for NaN and Inf, which do not exist in MPF. The erange flag is now set in these cases, and `mpfr_get_f` now returns the usual ternary value.
- `mpfr_get_si`, `mpfr_get_sj`, `mpfr_get_ui` and `mpfr_get_uj` changed in MPFR 3.0. In previous MPFR versions, the cases where the erange flag is set were unspecified.
- `mpfr_get_str` changed in MPFR 4.0. This function now sets the NaN flag on NaN input (to follow the usual MPFR rules on NaN and IEEE 754 recommendations on string conversions from Subclause 5.12.1) and sets the inexact flag when the conversion is inexact.
- `mpfr_get_z` changed in MPFR 3.0. The return type was `void`; it is now `int`, and the usual ternary value is returned. Thus programs that need to work with both MPFR 2.x and 3.x must not use the return value. Even in this case, C code using `mpfr_get_z` as the second or third term of a conditional operator may also be affected. For instance, the following is correct with MPFR 3.0, but not with MPFR 2.x:

      bool ? mpfr_get_z(...) : mpfr_add(...);

  On the other hand, the following is correct with MPFR 2.x, but not with MPFR 3.0:

      bool ? mpfr_get_z(...) : (void) mpfr_add(...);

  Portable code should cast `mpfr_get_z(...)` to `void` to use the type `void` for both terms of the conditional operator, as in:

      bool ? (void) mpfr_get_z(...) : (void) mpfr_add(...);

  Alternatively, `if ... else` can be used instead of the conditional operator.

  Moreover the cases where the erange flag is set were unspecified in MPFR 2.x.

- `mpfr_get_z_exp` changed in MPFR 3.0. In previous MPFR versions, the cases where the erange flag is set were unspecified. Note: this function has been renamed to `mpfr_get_z_2exp` in MPFR 3.0, but `mpfr_get_z_exp` is still available for compatibility reasons.
- `mpfr_out_str` changed in MPFR 4.1. The argument base can now be negative (from −2 to −36), in order to follow `mpfr_get_str` and GMP’s `mpf_out_str` functions.
- `mpfr_set_exp` changed in MPFR 4.0. Before MPFR 4.0, the exponent was set whatever the contents of the MPFR object in argument. In practice, this could be useful as a low-level function when the MPFR number was being constructed by setting the fields of its internal structure, but the API does not provide a way to do this except by using internals. Thus, for the API, this behavior was useless and could quickly lead to undefined behavior due to the fact that the generated value could have an invalid format if the MPFR object contained a special value (NaN, infinity or zero).
- `mpfr_strtofr` changed in MPFR 2.3.1 and MPFR 2.4. This was actually a bug fix since the code and the documentation did not match. But both were changed in order to have a more consistent and useful behavior. The main changes in the code are as follows. The binary exponent is now accepted even without the ‘`0b`’ or ‘`0x`’ prefix. Data corresponding to NaN can now have an optional sign (such data were previously invalid).
- `mpfr_strtofr` changed in MPFR 3.0. This function now accepts bases from 37 to 62 (no changes for the other bases). Note: if an unsupported base is provided to this function, the behavior is undefined; more precisely, in MPFR 2.3.1 and later, providing an unsupported base yields an assertion failure (this behavior may change in the future).
- `mpfr_subnormalize` changed in MPFR 3.1. This was actually regarded as a bug fix. The `mpfr_subnormalize` implementation up to MPFR 3.0.0 did not change the flags. In particular, it did not follow the generic rule concerning the inexact flag (and no special behavior was specified). The case of the underflow flag was more a lack of specification.
- `mpfr_sum` changed in MPFR 4.0. The `mpfr_sum` function has completely been rewritten for MPFR 4.0, with an update of the specification: the sign of an exact zero result is now specified, and the return value is now the usual ternary value. The old `mpfr_sum` implementation could also take all the memory and crash on inputs of very different magnitude.
- `mpfr_urandom` and `mpfr_urandomb` changed in MPFR 3.1. Their behavior no longer depends on the platform (assuming this is also true for GMP’s random generator, which is not the case between GMP 4.1 and 4.2 if `gmp_randinit_default` is used). As a consequence, the returned values can be different between MPFR 3.1 and previous MPFR versions. Note: as the reproducibility of these functions was not specified before MPFR 3.1, the MPFR 3.1 behavior is not regarded as backward incompatible with previous versions.
- `mpfr_urandom` changed in MPFR 4.0. The next random state no longer depends on the current exponent range and the rounding mode. The exceptions due to the rounding of the random number are now correctly generated, following the uniform distribution. As a consequence, the returned values can be different between MPFR 4.0 and previous MPFR versions.
- Up to MPFR 4.1.0, some macros of the Custom Interface had undocumented limitations. In particular, their arguments may be evaluated multiple times or none.