Add ifloor, iceil and itrunc to BigFloat (JuliaLang#3040)

They convert to a Int64 if it fits, otherwise to BigInt.

base/mpfr.jl

@@ -21,7 +21,7 @@ import
         isinf, isnan, ldexp, log, log2, log10, max, min, mod, modf, nextfloat,
         prevfloat, promote_rule, rem, round, show, showcompact, sum, sqrt,
         string, trunc, get_precision, exp10, expm1, gamma, lgamma, digamma,
-        erf, erfc, zeta, log1p, airyai,
+        erf, erfc, zeta, log1p, airyai, iceil, ifloor, itrunc,
     # import trigonometric functions
         sin, cos, tan, sec, csc, cot, acos, asin, atan, cosh, sinh, tanh,
         sech, csch, coth, acosh, asinh, atanh, atan2
@@ -347,6 +347,20 @@ for f in (:ceil, :floor, :trunc)
     end
 end
 
+for (f, g) in ((:iceil, :ceil), (:ifloor, :floor), (:itrunc, :trunc))
+    @eval begin
+        function ($f)(x::BigFloat)
+            fits = ccall((:mpfr_fits_slong_p, :libmpfr), Int32, (Ptr{BigFloat}, Int32), &x, RoundUp)
+            if fits != 0
+                z = BigFloat()
+                ccall(($(string(:mpfr_,g)), :libmpfr), Int32, (Ptr{BigFloat}, Ptr{BigFloat}), &z, &x)
+                return ccall((:mpfr_get_si, :libmpfr), Clong, (Ptr{BigFloat}, Int32), &z, ROUNDING_MODE[end])
+            end
+            return convert(BigInt, ($g)(x))
+        end
+    end
+end
+
 function ^(x::BigFloat, y::Unsigned)
     z = BigFloat()
     ccall((:mpfr_pow_ui, :libmpfr), Int32, (Ptr{BigFloat}, Ptr{BigFloat}, Culong, Int32), &z, &x, y, ROUNDING_MODE[end])

test/mpfr.jl

@@ -359,6 +359,32 @@ with_bigfloat_precision(53) do
     @test ldexp(BigFloat(24.5), 0x48) == ldexp(24.5, 72)
 end
 
+# ceil / iceil / floor / ifloor / trunc / itrunc
+x = BigFloat("28273.2312487489135135135")
+y = BigInt(28273)
+z = BigInt(28274)
+a = BigFloat("123456789012345678901234567890.2414")
+b = BigInt("123456789012345678901234567890")
+c = BigInt("123456789012345678901234567891")
+@test ceil(x) == z
+@test typeof(ceil(x)) == BigFloat
+@test floor(x) == y
+@test typeof(floor(x)) == BigFloat
+@test trunc(x) == y
+@test typeof(trunc(x)) == BigFloat
+@test iceil(x) == z
+@test typeof(iceil(x)) == Int64
+@test ifloor(x) == y
+@test typeof(ifloor(x)) == Int64
+@test itrunc(x) == y
+@test typeof(itrunc(x)) == Int64
+@test iceil(a) == c
+@test typeof(iceil(a)) == BigInt
+@test ifloor(a) == b
+@test typeof(ifloor(a)) == BigInt
+@test itrunc(a) == b
+@test typeof(itrunc(a)) == BigInt
+
 # basic arithmetic
 # Signed addition
 a = BigFloat("123456789012345678901234567890")