move DirectIndexString from Base

src/LegacyStrings.jl

@@ -5,6 +5,7 @@ __precompile__(true)
 module LegacyStrings
 
 export
+    DirectIndexString,
     ByteString,
     ASCIIString,
     RepString,
@@ -97,4 +98,11 @@ using Compat
     else
         include("rep.jl")
     end
+
+    if isdefined(Base, :DirectIndexString)
+        using Base: DirectIndexString
+    else
+        include("directindex.jl")
+    end
+
 end # module

src/directindex.jl

@@ -0,0 +1,34 @@
+# This file includes code that was formerly a part of Julia. License is MIT: http://julialang.org/license
+
+abstract type DirectIndexString <: AbstractString end
+
+next(s::DirectIndexString, i::Int) = (s[i],i+1)
+
+length(s::DirectIndexString) = endof(s)
+
+isvalid(s::DirectIndexString, i::Integer) = (start(s) <= i <= endof(s))
+
+prevind(s::DirectIndexString, i::Integer) = Int(i)-1
+nextind(s::DirectIndexString, i::Integer) = Int(i)+1
+
+function prevind(s::DirectIndexString, i::Integer, nchar::Integer)
+    nchar > 0 || throw(ArgumentError("nchar must be greater than 0"))
+    Int(i)-nchar
+end
+
+function nextind(s::DirectIndexString, i::Integer, nchar::Integer)
+    nchar > 0 || throw(ArgumentError("nchar must be greater than 0"))
+    Int(i)+nchar
+end
+
+ind2chr(s::DirectIndexString, i::Integer) = begin checkbounds(s,i); i end
+chr2ind(s::DirectIndexString, i::Integer) = begin checkbounds(s,i); i end
+
+length(s::SubString{<:DirectIndexString}) = endof(s)
+
+isvalid(s::SubString{<:DirectIndexString}, i::Integer) = (start(s) <= i <= endof(s))
+
+ind2chr(s::SubString{<:DirectIndexString}, i::Integer) = begin checkbounds(s,i); i end
+chr2ind(s::SubString{<:DirectIndexString}, i::Integer) = begin checkbounds(s,i); i end
+
+reverseind(s::Union{DirectIndexString,SubString{DirectIndexString}}, i::Integer) = length(s) + 1 - i