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### TODO

More a list of what could be done, rather than what should be done (which may be a much smaller list!).

- Add back-end support for libdecNumber.
- Add an adaptor back-end for complex number types.
- Add better multiplication routines (Karatsuba, FFT etc) to cpp_int_backend.
- Add assembly level routines to cpp_int_backend.
- Can ring types (exact floating-point types) be supported? The answer should be yes, but someone needs to write it, the hard part is IO and binary-decimal conversion.
- Should there be a choice of rounding mode (probably MPFR specific)?
- We can reuse temporaries in multiple subtrees (temporary caching).
- cpp_dec_float should round to nearest.
- A 2's complement fixed precision int that uses exactly N bits and no more.

Things requested in review:

- The performances of mp_number<a_trivial_adaptor<float>, false>respect to float and mp_number<a_trivial_adaptor<int>, false> and int should be given to show the cost of using the generic interface (Mostly done, just need to update docs to the latest results).
- Should we provide min/max overloads for expression templates? (Not done - we can't overload functions declared in the std namespace :-( ).
- The rounding applied when converting must be documented (Done).
- Document why we don't abstract out addition/multiplication algorithms etc. (done - FAQ)
- Document why we don't use proto (compile times) (Done).
- We can reuse temporaries in multiple subtrees (temporary caching) Moved to TODO list.
- Emphasise in the docs that ET's may reorder operations (done 2012/10/31).
- Document what happens to small fixed precision cpp_int's (done 2012/10/31).
- The use of bool in template parameters could be improved by the use of an enum class which will be more explicit. E.g `enum class expression_template {disabled, enabled}; enum class sign {unsigned, signed};` (Partly done 2012/09/15, done 2012/10/31).
- Each back-end should document the requirements it satisfies (not currently scheduled for inclusion: it's deliberately an implementation detail, and "optional" requirements are optimisations which can't be detected by the user). Not done: this is an implementation detail, the exact list of requirements satisfied is purely an optimization, not something the user can detect.
- A backend for an overflow aware integers (done 2012/10/31).
- IIUC convert_to is used to emulate in c++98 compilers C++11 explicit conversions. Could the explicit conversion operator be added on compilers supporting it? (Done 2012/09/15).
- The front-end should make the differences between implicit and explicit construction (Done 2012/09/15).
- The tutorial should add more examples concerning implicit or explicit conversions. (Done 2012/09/15).
- The documentation must explain how move semantics helps in this domain and what the backend needs to do to profit from this optimization. (Done 2012/09/15).
- The documentation should contain Throws specification on the mp_number and backend requirements operations. (Done 2012/09/15).
- The library interface should use the noexcept (BOOST_NOEXCEPT, ...) facilities (Done 2012/09/15).
- It is unfortunate that the generic mp_number front end can not make use constexpr as not all the backends can ensure this (done - we can go quite a way).
- literals: The library doesn't provide some kind of literals. I think that the mp_number class should provide a way to create literals if the backend is able to. (Done 2012/09/15).
- The ExpresionTemplate parameter could be defaulted to a traits class for more sensible defaults (done 2012/09/20).
- In a = exp1 op exp2 where a occurs inside one of exp1 or exp2 then we can optimise and eliminate one more temporary (done 2012/09/20).

##### Pre-Review Comments

- Make fixed precision orthogonal to Allocator type in cpp_int. Possible solution - add an additional MaxBits template argument that defaults to 0 (meaning keep going till no more space/memory). Done.
- Can ring types (exact floating-point types) be supported? The answer should be yes, but someone needs to write it (Moved to TODO list).
- Should there be a choice of rounding mode (probably MPFR specific)? Moved to TODO list.
- Make the exponent type for cpp_dec_float a template parameter, maybe include support for big-integer exponents. Open question - what should be the default - int32_t or int64_t? (done 2012/09/06)
- Document the size requirements of fixed precision ints (done 2012/09/15).
- Document std lib function accuracy (done 2012/09/15).
- Be a bit clearer on the effects of sign-magnitude representation of cpp_int - min == -max etc - done.
- Document cpp_dec_float precision, rounding, and exponent size (done 2012/09/06).
- Can we be clearer in the docs that mixed arithmetic doesn't work (no longer applicable as of 2012/09/06)?
- Document round functions behaviour better (they behave as in C++11) (added note 2012/09/06).
- Document limits on size of cpp_dec_float (done 2012/09/06).
- Add support for fused multiply add (and subtract). GMP mpz_t could use this (done 2012/09/20).