Read(“count_heads.jl”, String) conversion error

Specific Domains Julia at Scale
,
1

I am going through Parallel Loops and Maps and I am seeming to have difficulty with even accessing the file count_heads.jl

I saved it in my working directory

function count_heads(n)
	c::Int = 0
	for i = 1:n
		c += rand(Bool)
	end
	c
end

And I can verify it’s existence in that directory:

filter(r"count_heads.jl", readdir())
#1-element Array{String,1}:
#"count_heads.jl"

Yet when I attempt the next step in the tutorial.

@everywhere include_string(Main, $(read("count_heads.jl", String)), "count_heads.jl")
ERROR: MethodError: Cannot `convert` an object of type Type{String} to an object of type Array{UInt8,1}
This may have arisen from a call to the constructor Array{UInt8,1}(...),
since type constructors fall back to convert methods.

Looking at just the read("count_heads.jl", String) function I get the source of the error (I think).

2

x-ref: Julia: read("count_heads.jl", String) conversion error - Stack Overflow

3

Yeah, I don’t know what the issue is. Maybe not a good SO question.

4

I think read("count_heads.jl", String) is valid only for Julia v0.7.

For earlier versions, you can either use readstring("count_heads.jl"), which is deprecated in v0.7.
Or to use the new syntax, using Compat; read("count_heads.jl", String)

5

It works on 0.6. @EconometricsBySimula are you on 0.5? Then you should use the appropriate version of the documentation.

6

Are you sure?

AFAICT, readstring was deprecated to read(io, String), but that PR (Deprecate readstring in favor of read(io, String) by jpfairbanks · Pull Request #22864 · JuliaLang/julia · GitHub) didn’t make it into v0.6.

On v0.6 or earlier, you can either use readstring("count_heads.jl"), or write using Compat before the new syntax read("count_heads.jl", String).

Also note that read(filename, String) should work in Juno, since Juno is implicitly using Compat.

7 
               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0 (2017-06-19 13:05 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-apple-darwin13.4.0

julia> @everywhere include_string(Main, $(read("count_heads.jl", String)), "count_heads.jl")

works, at least.

8

Very strange.

               _
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation: https://docs.julialang.org
   _ _   _| |_  __ _   |  Type "?help" for help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.6.0 (2017-06-19 13:05 UTC)
 _/ |\__'_|_|_|\__'_|  |  Official http://julialang.org/ release
|__/                   |  x86_64-w64-mingw32

Julia-0.6.0> @everywhere include_string(Main, $(read("count_heads.jl", String)), "count_heads.jl")
ERROR: MethodError: Cannot `convert` an object of type Type{String} to an object of type Array{UInt8,1}
This may have arisen from a call to the constructor Array{UInt8,1}(...),
since type constructors fall back to convert methods.
read(::IOStream, ::Type{T} where T) at .\io.jl:528
open(::Base.##190#191{Tuple{DataType}}, ::String) at .\iostream.jl:152
(::##1#3)() at .\distributed\macros.jl:102
Stacktrace:
 [1] sync_end() at .\task.jl:287
 [2] macro expansion at .\distributed\macros.jl:112 [inlined]
 [3] anonymous at .\<missing>:?

Perhaps a difference in Windows and Mac?

You don’t have using Compat in your .juliarc.jl? (can see if Compat is loaded by running whos())

1 Like
9

Well, what do you know, that’s it :slight_smile: I have using OhMyREPL in my .juliarc.jl file, and that loads Compat.