Operations: exponentiation

[tinybike]

No description provided.

[longemen3000]

this works in a way, it takes care of all irrational cases by going into bigfloat, if not, then the Decimal fields
are calculated manually

function ^(x::Decimal, y::Decimal)
    #(-1.23)^(something) code to catch errors prior to the routine
    x.s == 1 && begin
        (y.q < 0  && throw(DomainError(y),"Exponentiation yielding a complex result requires a complex argument."))
    end
    y.s == 1 && (return ^(inv(x),-y))
    y.q < 0 && (return Decimal(BigFloat(x)^BigFloat(y))) #add correction to precision, its too much
    
    if iseven(y.c) #squared number
        zs = 0
    else
        if x.s == 0 
            zs =0
        else
            zs = 1
        end
    end
    
        zc = x.c^((y.c)*(10^y.q))
        zq = (x.q)*((y.c)*(10^y.q))
        return  Decimal(zs,zc,zq)
 
end

[StevenSiew]

Here is source code to show how to perform exponentiation

using Decimals
import Base.sqrt

function SciNota(x::Decimal)
    prec = precision(Decimal)
    str = string(x.c)
    strlen = length(str)
    expo_adj = strlen - 1
    if strlen > prec
        str = str[1:prec]
    else
        while length(str) < prec
            str = str * "0"
        end
    end
    return (Int64(x.s),str,x.q + expo_adj)
end

function SciString(x::Decimal)
    (sign,str,expo) = SciNota(x)
    result = sign == 1 ? "-" : ""
    result = result * str[1] * "." * str[2:end] * "e" * string(expo)
    return result
end

function sqrt(x::Decimal;guard_digits=6)
    x_str = SciString(x)
    local z_str
    setprecision(BigFloat, precision(Decimal) + guard_digits; base=10) do
        z_str      = string(  Base.sqrt(parse(BigFloat,x_str))  )
    end
    z = parse(Decimal,z_str)
    return z
end

function power(x::Decimal,y::Decimal;guard_digits=6)
    x_str = SciString(x)
    y_str = SciString(y)
    local z_str
    setprecision(BigFloat, precision(Decimal) + guard_digits; base=10) do
        z_str      = string(  parse(BigFloat,x_str) ^ parse(BigFloat,y_str)  )
    end
    z = parse(Decimal,z_str)
    return z
end

x = Decimal(0,5,-1)
y = sqrt(dec"3")

println("start of program")
println( SciNota(x) )
println( SciString(x) )
println( string(power(x,y)) )

[barucden]

Ideally, we'd like to avoid conversions from/to String. @longemen3000 has already proposed a baseline implementation (#33), but it needs more work. You can offer help, if you'd like.