Logging interface

Log.jl

module Log

export AbstractLogger, call, logging
import Base: call, getindex

@enum Level OFF=0 FATAL=100 ERROR=200 WARN=300 INFO=400 DEBUG=500 TRACE=600 ALL=1000

abstract AbstractLogger
type LogWrapper{T <: AbstractLogger}
    logger::T
    warn::Function
    LogWrapper(l) = new(l)
end
LogWrapper{T <: AbstractLogger}(l::T) = LogWrapper{T}(l)
function create{L<:AbstractLogger}(l::L)
    w = LogWrapper(l)
    w.warn = (msg...)->logging(w.logger, WARN, msg...)
    return w
end
call(wrapper::LogWrapper, msg...) = logging(wrapper.logger, msg...)
getindex(wrapper::LogWrapper, level::Level) = (msg...)->logging(wrapper.logger, level, msg...)

"This function is common interface"
function logging end

end

using_log.jl

import Log
import Log: create, WARN

# Definition of backend
type IOLogger <: Log.AbstractLogger
    io::IO
end
Log.logging(l::IOLogger, msg...) = println(l.io, "=>", msg...)

# Create logging object
lgr = Log.create(IOLogger(STDOUT))
lgr[WARN](1, " a ", 0.9)
lgr.warn(1, " a ", 0.9)
lgr(1, " a ", 0.9)