stillwater-sc / universal / 25962306993

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Commit Message

feat(integer, fixpnt): migrate/implement parse() onto string_parse (Phase B1 of #835) (#839)

* feat(integer, fixpnt): migrate/implement parse() onto string_parse (Phase B1 of #835)

Phase B1 of issue #835: bring `integer` and `fixpnt` onto the shared
constexpr string-parsing foundation that landed in Phase A (#838).

integer
-------
Replaces the std::regex + std::map + reverse-iteration parser body in
parse(const std::string&, integer&) with a clean MSB-first scan that
delegates prefix/sign detection and character classification to the
`sw::universal::string_parse` primitives.

Notable functional changes:
  - The previous octal branch was a `// TODO` that always returned false
    after detecting C-style leading-zero octal. Replaced with a real
    implementation gated on the explicit `0o` / `0O` prefix.
  - Binary (`0b` / `0B`) is newly supported.
  - Hex still accepts apostrophe as a digit separator (e.g. `0xDE'AD').
  - Decimal accepts a single optional leading `+` or `-`.
  - Drops the `<regex>` and `<map>` includes from integer_impl.hpp.

fixpnt
------
`fixpnt::parse()` was previously forward-declared (fixpnt_fwd.hpp:22) and
called by `operator>>` (fixpnt_impl.hpp:2073) but had no definition --
a latent link error that nobody had hit because no test exercises stream
input on fixpnt. This PR provides the definition.

Accepted syntax:
  [+-]? ( 0[bB][01]+ | 0[oO][0-7]+ | 0[xX][0-9A-F']+ | [0-9]+ )

Bit-pattern parsing (binary / octal / hex) fills the underlying storage
MSB-first via setbit(0) + left shift -- matches the convention of
setbits(). Decimal parsing is integer-only in this phase: the digit
string is accumulated as an integer K and stored as `K << rbits`, so
parse("5") on fixpnt<8,4> yields the value 5.0. Decimal-fraction
parsing ("3.14") is deferred to Phase B2 along with the analogous
float-from-string work for posit and cfloat.

Tests
-----
- static/integer/binary/api/string_parse.cpp -- 33 assertions covering
  decimal, binary, octal... (continued)

Coverage Stats

104 of 110 new or added lines in 2 files covered. (94.55%)

1 existing line in 1 file now uncovered.

46103 of 54895 relevant lines covered (83.98%)

6455983.32 hits per line