# Compat usage

**URL:** <https://discourse.julialang.org/t/compat-usage/12591>\
**Category:** General Usage\
**Created:** [July 23, 2018, 3:18am UTC](https://discourse.julialang.org/t/compat-usage/12591 "2018-07-23T03:18:14Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![John\_Gibson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/john_gibson/32/5321_2.png) [@John\_Gibson](https://discourse.julialang.org/u/John_Gibson)\
**Post date:** [July 23, 2018, 3:18am UTC](https://discourse.julialang.org/t/compat-usage/12591/1 "2018-07-23T03:18:14Z")

</div>

How do I use Compat.jl to get this julia-0.7 code running on 0.6 as well? (the code’s from the Julia Microbenchmarks)

```julia
function parseintperf(t)
    local n, m
    for i=1:t
        n = rand(UInt32)
        s = string(n, base = 16) # was s = hex(n) in 0.6
        m = UInt32(parse(Int64, s, base = 16)) # was m = UInt32(parse(Int64, s, 16)) in 0.6
        @assert m == n
    end
    return n
end

```

Prefacing the key lines with `@compat` as suggested by the [Compat.jl README](https://github.com/JuliaLang/Compat.jl) doesn’t work. There doesn’t seem to be anything relevant in the README’s list of special cases, either.

```julia
using Compat
import Compat.String

function parseintperf(t)
    local n, m
    for i=1:t
        n = rand(UInt32)
        @compat s = string(n, base = 16)
        @compat m = UInt32(parse(Int64, s, base = 16))
        @assert m == n
    end
    return n
end

```

This runs fine under 0.7 but not under 0.6.

```julia
julia> include("parseintperf.jl")
parseintperf (generic function with 1 method)

julia> parseintperf(100)
ERROR: function string does not accept keyword arguments
Stacktrace:
 [1] kwfunc(::Any) at ./boot.jl:237
 [2] parseintperf(::Int64) at /home/gibson/scratch/julia/parseintperf.jl:8

julia> versioninfo()
Julia Version 0.6.3
Commit d55cadc350 (2018-05-28 20:20 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: Intel(R) Core(TM) i5-6300U CPU @ 2.40GHz
  WORD_SIZE: 64
  BLAS: libopenblas (USE64BITINT DYNAMIC_ARCH NO_AFFINITY Haswell)
  LAPACK: libopenblas64_
  LIBM: libopenlibm
  LLVM: libLLVM-3.9.1 (ORCJIT, skylake)

```

I could use a working example of Compat usage.

---

<div class="post-metadata">

**Author:** ![John\_Gibson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/john_gibson/32/5321_2.png) [@John\_Gibson](https://discourse.julialang.org/u/John_Gibson)\
**Post date:** [July 23, 2018, 6:24pm UTC](https://discourse.julialang.org/t/compat-usage/12591/2 "2018-07-23T18:24:39Z")

</div>

Answer, from @ararslan and @ChrisRackauckas on [https://julialang.slack.com](https://julialang.slack.com): The correct syntax is

```julia
using Compat
using Compat: string, parse

function parseintperf(t)
    local n, m
    for i=1:t
        n = rand(UInt32)
        @compat s = string(n, base = 16)
        @compat m = UInt32(parse(Int64, s, base = 16))
        @assert m == n
    end
    return n
end

```

However this doesn’t work because Compat doesn’t have the 0.7-style string with keyword arguments. So instead do this

```julia
function parseintperf(t)
    local n, m

    for i=1:t
        n = rand(UInt32)
        @static if VERSION >= v"0.7.0-DEV.4446"
            s = string(n, base = 16)
            m = UInt32(parse(Int64, s, base = 16))
        else
            s = hex(n)
            m = UInt32(parse(Int64, s, 16))
        end
        @assert m == n
    end
    return n
end

```

You can also do this more slickly by defining function closures like `_hex(n) = string(n, base=16)` inside an `if VERSION` statement prior to the for loop, but this has a little overhead I don’t want in the benchmarks.