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digits(n, [base, [pad]]): returns an array of digits of n [close #2737]
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@StefanKarpinski
StefanKarpinski committed Apr 4, 2013
1 parent 3eb0c05 commit 0d22e92
Showing 1 changed file with 12 additions and 1 deletion.
13 changes: 12 additions & 1 deletion base/intfuncs.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -291,7 +291,6 @@ base(base::Integer, n::Integer, pad::Integer) = _base(dig_syms,int(base),unsigne
base(symbols::Array{Uint8}, n::Integer, p::Integer) = _base(symbols,length(symbols),unsigned(abs(n)),p,n<0)
base(base_or_symbols::Union(Integer,Array{Uint8}), n::Integer) = base(base_or_symbols, n, 1)


for sym in (:bin, :oct, :dec, :hex)
@eval begin
($sym)(x::Unsigned, p::Int) = ($sym)(x,p,false)
Expand All @@ -307,6 +306,18 @@ bits(x::Union(Char,Int32,Uint32,Float32)) = bin(reinterpret(Uint32,x),32)
bits(x::Union(Int64,Uint64,Float64)) = bin(reinterpret(Uint64,x),64)
bits(x::Union(Int128,Uint128)) = bin(reinterpret(Uint128,x),128)

function digits{T<:Integer}(n::Integer, base::T=10, pad::Int=1)
2 <= base || error("invalid base: $base")
i = max(pad,ndigits0z(n,base))
a = zeros(T,i)
while i > 0
a[i] = rem(n,base)
n = div(n,base)
i -= 1
end
return a
end

const PRIMES = [
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
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3 comments on commit 0d22e92

@JeffBezanson
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It seems more useful to me to return the digits in the reverse order of this, i.e. with the ones place always in a[1]. That way the place values are the same for all numbers, and the identity n == sum([a[k]*b^(k-1) for k=1:length(a)]) holds.

@StefanKarpinski
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That seems reasonable enough. This was just the order they print in.

@alanedelman
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... and it respects column major order too.

Can we generalize to take a base vector like APL's encode, (and also inspired by a "zero based" Cartesian)
(note the code is practically the same)

function Alandigits(n,base::Array,pad::Int=1)
    k=length(base);
    a=zeros(Int,max(k,pad));i=k;
    for i=k:-1:1
        a[k+1-i] = rem(n,base[i])
        n = div(n,base[i])
    end
   a
 end

map(n->Alandigits(n,[5,3],3),0:14)
15-element Array{Array{Int64,1},1}:
[0,0,0]
[1,0,0]
[2,0,0]
[0,1,0]
[1,1,0]
[2,1,0]
[0,2,0]
[1,2,0]
[2,2,0]
[0,3,0]
[1,3,0]
[2,3,0]
[0,4,0]
[1,4,0]
[2,4,0]

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