Make precision a keyword argument, improve handling of rounding mode. (…

…JuliaLang#29157)

* Improve handling of precision and rounding mode arguments in BigFloat constructors.

This makes a few changes to avoid unnecessarily calling `setrounding` and `setprecision`. It also changes `precision` to be a keyword argument (though does not yet deprecate the old behaviour).

NEWS.md

@@ -11,7 +11,9 @@ Language changes
 ----------------
 
  * the constructor `BigFloat(::BigFloat)` now respects the global precision setting and always
- returns a `BigFloat` with precision equal to `precision(BigFloat)` ([#29127]).
+ returns a `BigFloat` with precision equal to `precision(BigFloat)` ([#29127]). The optional
+ `precision` argument to override the global setting is now a keyword instead of positional
+ argument ([#29157]).
  * Parser inputs ending with a comma are now consistently treated as incomplete.
  Previously they were sometimes parsed as tuples, depending on whitespace ([#28506]).
  * `Regex` now behave like a scalar when used in broadcasting ([#29913]).

base/deprecated.jl

@@ -168,4 +168,9 @@ function promote_eltype_op end
 one(::CartesianIndex{N}) where {N} = one(CartesianIndex{N})
 one(::Type{CartesianIndex{N}}) where {N} = CartesianIndex(ntuple(x -> 1, Val(N)))
 
+MPFR.BigFloat(x, prec::Int) = BigFloat(x; precision=prec)
+MPFR.BigFloat(x, prec::Int, rounding::RoundingMode) = BigFloat(x, rounding; precision=prec)
+MPFR.BigFloat(x::Real, prec::Int) = BigFloat(x; precision=prec)
+MPFR.BigFloat(x::Real, prec::Int, rounding::RoundingMode) = BigFloat(x, rounding; precision=prec)
+
 # END 1.0 deprecations

base/irrationals.jl

@@ -147,14 +147,18 @@ macro irrational(sym, val, def)
  esym = esc(sym)
  qsym = esc(Expr(:quote, sym))
  bigconvert = isa(def,Symbol) ? quote
- function Base.BigFloat(::Irrational{$qsym})
- c = BigFloat()
+ function Base.BigFloat(::Irrational{$qsym}, r::MPFR.MPFRRoundingMode=MPFR.ROUNDING_MODE[]; precision=precision(BigFloat))
+ c = BigFloat(;precision=precision)
  ccall(($(string("mpfr_const_", def)), :libmpfr),
- Cint, (Ref{BigFloat}, Int32), c, MPFR.ROUNDING_MODE[])
+ Cint, (Ref{BigFloat}, MPFR.MPFRRoundingMode), c, r)
  return c
  end
  end : quote
- Base.BigFloat(::Irrational{$qsym}) = $(esc(def))
+ function Base.BigFloat(::Irrational{$qsym}; precision=precision(BigFloat))
+ setprecision(BigFloat, precision) do
+ $(esc(def))
+ end
+ end
  end
  quote
  const $esym = Irrational{$qsym}()