Context

src/Decimals.jl

@@ -21,6 +21,7 @@ struct Decimal <: AbstractFloat
 end
 
 include("bigint.jl")
+include("context.jl")
 
 # Convert between Decimal objects, numbers, and strings
 include("decimal.jl")

src/arithmetic.jl

@@ -4,7 +4,8 @@ Base.promote_rule(::Type{Decimal}, ::Type{<:Real}) = Decimal
 Base.promote_rule(::Type{BigFloat}, ::Type{Decimal}) = Decimal
 Base.promote_rule(::Type{BigInt}, ::Type{Decimal}) = Decimal
 
-const BigTen = BigInt(10)
+Base.:(+)(x::Decimal) = fixed(x)
+Base.:(-)(x::Decimal) = fixed(Decimal(!x.s, x.c, x.q))
 
 # Addition
 # To add, convert both decimals to the same exponent.
@@ -24,9 +25,6 @@ function Base.:(+)(x::Decimal, y::Decimal)
     return normalize(Decimal(s, abs(c), y.q))
 end
 
-# Negation
-Base.:(-)(x::Decimal) = Decimal(!x.s, x.c, x.q)
-
 # Subtraction
 Base.:(-)(x::Decimal, y::Decimal) = +(x, -y)
 

src/bigint.jl

@@ -4,6 +4,8 @@ else
     const libgmp = Base.GMP.libgmp
 end
 
+const BigTen = BigInt(10)
+
 function isdivisible(x::BigInt, n::Int)
     r = ccall((:__gmpz_divisible_ui_p, libgmp), Cint,
               (Base.GMP.MPZ.mpz_t, Culong), x, n)

src/context.jl

@@ -0,0 +1,95 @@
+# Number of significant digits
+const PRECISION = Ref(9)
+const ROUNDING = Ref{RoundingMode}(RoundNearest)
+const EMAX = Ref(99999)
+const EMIN = Ref(-99999)
+
+function Base.setprecision(::Type{Decimal}, precision::Int)
+    PRECISION[] = precision
+    return precision
+end
+Base.precision(::Type{Decimal}) = PRECISION[]
+
+function Base.setrounding(::Type{Decimal}, rounding::RoundingMode)
+    ROUNDING[] = rounding
+    return rounding
+end
+Base.rounding(::Type{Decimal}) = ROUNDING[]
+
+"""
+    fixed(x)
+
+Round `x` if necessary to keep within `PRECISION`.
+"""
+function fixed(x::Decimal)
+    prec = precision(Decimal)
+    rmod = rounding(Decimal)
+
+    Emin, Emax = EMIN[], EMAX[]
+    Etiny = Emin - prec + 1
+    Etop = Emax - prec + 1
+
+    if iszero(x)
+        return Decimal(x.s, x.c, clamp(x.q, Etiny, Etop))
+    end
+
+    clen = ndigits(x.c)
+    exp_min = clen + x.q - prec
+
+    if exp_min > Etop
+        throw(OverflowError("Exponent limit ($Emax) exceeded: $x"))
+    end
+
+    subnormal = exp_min < Etiny
+    if subnormal
+        exp_min = Etiny
+    end
+
+    # Number of digits and exponent within bounds
+    if x.q ≥ exp_min
+        return x
+    end
+
+    # Signed coefficient for rounding modes like RoundToZero
+    c = (-1)^x.s * x.c
+    q = exp_min
+
+    # Number of digits of the resulting coefficient
+    digits = clen + x.q - exp_min
+    if digits < 0
+        c = big(1)
+        q = exp_min - 1
+        digits = 0
+    end
+
+    # Number of least significant digits to remove from `c`
+    trun_len = clen - digits
+
+    # Split `c` into `digits` most significant digits and `trun_len` least
+    # significant digits
+    # This is like round(c, rmod, sigdigits=digits), except here we can
+    # tell from `rem` if the rounding was lossless
+    c, rem = divrem(c, BigTen ^ trun_len, rmod)
+
+    # Rounding is exact if the truncated digits were zero
+    exact = iszero(rem)
+
+    # If the number of digits exceeded `digits` after rounding,
+    # it means that `c` was like 99...9 and was rounded up,
+    # becoming                  100...0, so `c` is divisible by 10
+    if ndigits(c) > prec
+        c = exactdiv(c, 10)
+        q += 1
+    end
+
+    # Exponent might have exceeded due to rounding
+    if q > Etop
+        throw(OverflowError("Exponent limit ($Emax) exceeded: $x"))
+    end
+
+    if subnormal && !exact
+        #            throw(ErrorException("Underflow"))
+    end
+
+    return Decimal(signbit(c), abs(c), q)
+end

test/runtests.jl

@@ -24,5 +24,7 @@ include("test_norm.jl")
 include("test_round.jl")
 
 include("test_compare.jl")
+include("test_minus.jl")
+include("test_plus.jl")
 
 end

test/test_minus.jl

@@ -0,0 +1,241 @@
+@testset "Minus" begin
+    setprecision(Decimal, 9)
+    setrounding(Decimal, RoundNearestTiesAway)
+    Decimals.EMAX[] = 384
+    Decimals.EMIN[] = -383
+
+    # minx001
+    @test -(dec"1") == dec"-1"
+    # minx002
+    @test -(dec"-1") == dec"1"
+    # minx003
+    @test -(dec"1.00") == dec"-1.00"
+    # minx004
+    @test -(dec"-1.00") == dec"1.00"
+    # minx005
+    @test -(dec"0") == dec"0"
+    # minx006
+    @test -(dec"0.00") == dec"0.00"
+    # minx007
+    @test -(dec"00.0") == dec"0.0"
+    # minx008
+    @test -(dec"00.00") == dec"0.00"
+    # minx009
+    @test -(dec"00") == dec"0"
+    # minx010
+    @test -(dec"-2") == dec"2"
+    # minx011
+    @test -(dec"2") == dec"-2"
+    # minx012
+    @test -(dec"-2.00") == dec"2.00"
+    # minx013
+    @test -(dec"2.00") == dec"-2.00"
+    # minx014
+    @test -(dec"-0") == dec"0"
+    # minx015
+    @test -(dec"-0.00") == dec"0.00"
+    # minx016
+    @test -(dec"-00.0") == dec"0.0"
+    # minx017
+    @test -(dec"-00.00") == dec"0.00"
+    # minx018
+    @test -(dec"-00") == dec"0"
+    # minx020
+    @test -(dec"-0e3") == dec"0e+3"
+    # minx021
+    @test -(dec"-0e2") == dec"0e+2"
+    # minx022
+    @test -(dec"-0e1") == dec"0e+1"
+    # minx023
+    @test -(dec"-0e0") == dec"0"
+    # minx024
+    @test -(dec"+0e0") == dec"0"
+    # minx025
+    @test -(dec"+0e1") == dec"0e+1"
+    # minx026
+    @test -(dec"+0e2") == dec"0e+2"
+    # minx027
+    @test -(dec"+0e3") == dec"0e+3"
+    # minx030
+    @test -(dec"-5e3") == dec"5e+3"
+    # minx031
+    @test -(dec"-5e8") == dec"5e+8"
+    # minx032
+    @test -(dec"-5e13") == dec"5e+13"
+    # minx033
+    @test -(dec"-5e18") == dec"5e+18"
+    # minx034
+    @test -(dec"+5e3") == dec"-5e+3"
+    # minx035
+    @test -(dec"+5e8") == dec"-5e+8"
+    # minx036
+    @test -(dec"+5e13") == dec"-5e+13"
+    # minx037
+    @test -(dec"+5e18") == dec"-5e+18"
+    # minx050
+    @test -(dec"-2000000") == dec"2000000"
+    # minx051
+    @test -(dec"2000000") == dec"-2000000"
+
+    setprecision(Decimal, 7)
+
+    # minx052
+    @test -(dec"-2000000") == dec"2000000"
+    # minx053
+    @test -(dec"2000000") == dec"-2000000"
+
+    setprecision(Decimal, 6)
+
+    # minx054
+    @test -(dec"-2000000") == dec"2.00000e+6"
+    # minx055
+    @test -(dec"2000000") == dec"-2.00000e+6"
+
+    setprecision(Decimal, 3)
+
+    # minx056
+    @test -(dec"-2000000") == dec"2.00e+6"
+    # minx057
+    @test -(dec"2000000") == dec"-2.00e+6"
+
+    setprecision(Decimal, 9)
+
+    # minx060
+    @test -(dec"56267e-10") == dec"-0.0000056267"
+    # minx061
+    @test -(dec"56267e-5") == dec"-0.56267"
+    # minx062
+    @test -(dec"56267e-2") == dec"-562.67"
+    # minx063
+    @test -(dec"56267e-1") == dec"-5626.7"
+    # minx065
+    @test -(dec"56267e-0") == dec"-56267"
+    # minx066
+    @test -(dec"56267e+0") == dec"-56267"
+    # minx067
+    @test -(dec"56267e+1") == dec"-5.6267e+5"
+    # minx068
+    @test -(dec"56267e+2") == dec"-5.6267e+6"
+    # minx069
+    @test -(dec"56267e+3") == dec"-5.6267e+7"
+    # minx070
+    @test -(dec"56267e+4") == dec"-5.6267e+8"
+    # minx071
+    @test -(dec"56267e+5") == dec"-5.6267e+9"
+    # minx072
+    @test -(dec"56267e+6") == dec"-5.6267e+10"
+    # minx080
+    @test -(dec"-56267e-10") == dec"0.0000056267"
+    # minx081
+    @test -(dec"-56267e-5") == dec"0.56267"
+    # minx082
+    @test -(dec"-56267e-2") == dec"562.67"
+    # minx083
+    @test -(dec"-56267e-1") == dec"5626.7"
+    # minx085
+    @test -(dec"-56267e-0") == dec"56267"
+    # minx086
+    @test -(dec"-56267e+0") == dec"56267"
+    # minx087
+    @test -(dec"-56267e+1") == dec"5.6267e+5"
+    # minx088
+    @test -(dec"-56267e+2") == dec"5.6267e+6"
+    # minx089
+    @test -(dec"-56267e+3") == dec"5.6267e+7"
+    # minx090
+    @test -(dec"-56267e+4") == dec"5.6267e+8"
+    # minx091
+    @test -(dec"-56267e+5") == dec"5.6267e+9"
+    # minx092
+    @test -(dec"-56267e+6") == dec"5.6267e+10"
+
+    Decimals.EMAX[] = 999999999
+    Decimals.EMIN[] = -999999999
+    setprecision(Decimal, 3)
+
+    # minx100
+    @test_throws OverflowError -(dec"9.999e+999999999")
+    # minx101
+    @test_throws OverflowError -(dec"-9.999e+999999999")
+
+    setprecision(Decimal, 3)
+    Decimals.EMAX[] = 999
+    Decimals.EMIN[] = -999
+
+    # minx110
+    @test -(dec"1.00e-999") == dec"-1.00e-999"
+    # minx111
+    @test -(dec"0.1e-999") == dec"-1e-1000"
+    # minx112
+    @test -(dec"0.10e-999") == dec"-1.0e-1000"
+    # minx113
+    @test -(dec"0.100e-999") == dec"-1.0e-1000"
+    # minx114
+    @test -(dec"0.01e-999") == dec"-1e-1001"
+    # minx115
+    @test -(dec"0.999e-999") == dec"-1.00e-999"
+    # minx116
+    @test -(dec"0.099e-999") == dec"-1.0e-1000"
+    # minx117
+    @test -(dec"0.009e-999") == dec"-1e-1001"
+    # minx118
+    @test -(dec"0.001e-999") == dec"-0e-1001"
+    # minx119
+    @test -(dec"0.0009e-999") == dec"-0e-1001"
+    # minx120
+    @test -(dec"0.0001e-999") == dec"-0e-1001"
+    # minx130
+    @test -(dec"-1.00e-999") == dec"1.00e-999"
+    # minx131
+    @test -(dec"-0.1e-999") == dec"1e-1000"
+    # minx132
+    @test -(dec"-0.10e-999") == dec"1.0e-1000"
+    # minx133
+    @test -(dec"-0.100e-999") == dec"1.0e-1000"
+    # minx134
+    @test -(dec"-0.01e-999") == dec"1e-1001"
+    # minx135
+    @test -(dec"-0.999e-999") == dec"1.00e-999"
+    # minx136
+    @test -(dec"-0.099e-999") == dec"1.0e-1000"
+    # minx137
+    @test -(dec"-0.009e-999") == dec"1e-1001"
+    # minx138
+    @test -(dec"-0.001e-999") == dec"0e-1001"
+    # minx139
+    @test -(dec"-0.0009e-999") == dec"0e-1001"
+    # minx140
+    @test -(dec"-0.0001e-999") == dec"0e-1001"
+
+    Decimals.EMAX[] = 999
+    Decimals.EMIN[] = -999
+    setprecision(Decimal, 9)
+
+    # minx301
+    @test -(dec"12345678000") == dec"-1.23456780e+10"
+    # minx302
+    @test -(dec"1234567800") == dec"-1.23456780e+9"
+    # minx303
+    @test -(dec"1234567890") == dec"-1.23456789e+9"
+    # minx304
+    @test -(dec"1234567891") == dec"-1.23456789e+9"
+    # minx305
+    @test -(dec"12345678901") == dec"-1.23456789e+10"
+    # minx306
+    @test -(dec"1234567896") == dec"-1.23456790e+9"
+
+    setprecision(Decimal, 15)
+
+    # minx321
+    @test -(dec"12345678000") == dec"-12345678000"
+    # minx322
+    @test -(dec"1234567800") == dec"-1234567800"
+    # minx323
+    @test -(dec"1234567890") == dec"-1234567890"
+    # minx324
+    @test -(dec"1234567891") == dec"-1234567891"
+    # minx325
+    @test -(dec"12345678901") == dec"-12345678901"
+    # minx326
+    @test -(dec"1234567896") == dec"-1234567896"
+end