[julia-users] isapprox Fallback

[Jared Crean]

I am comparing two arrays that contain both numbers and strings using 
FactCheck and got an error

  Error   :: (line:-1)
    data_code => roughly(data_ref,atol=1.0e-13)
MethodError: `isapprox` has no method matching 
isapprox(::SubString{ASCIIString}, ::SubString{ASCIIString})


so I defined a new method:

import Base.isapprox

# generic fallback
function isapprox(a::SubString{ASCIIString}, b::SubString{ASCIIString})
  return a == b
end


and now I get the error:

  Error   :: (line:-1)
    data_code => roughly(data_ref,atol=1.0e-13)
MethodError: `isapprox` has no method matching 
isapprox(::SubString{ASCIIString}, ::SubString{ASCIIString})
Closest candidates are:
  isapprox(::SubString{ASCIIString}, ::SubString{ASCIIString})


I get a similar error if I don't restrict the argument types of isapprox:

  Error   :: (line:-1)
    data_code => roughly(data_ref,atol=1.0e-13)
MethodError: `isapprox` has no method matching 
isapprox(::SubString{ASCIIString}, ::SubString{ASCIIString})
Closest candidates are:
  isapprox(::Any, ::Any)


In all cases the backtrace is:

 in anonymous at no file:46
 in anonymous at /users/creanj/.julia/v0.4/FactCheck/src/FactCheck.jl:140
 in anonymous at /users/creanj/.julia/v0.4/FactCheck/src/FactCheck.jl:142
 in do_fact at /users/creanj/.julia/v0.4/FactCheck/src/FactCheck.jl:201
 in anonymous at 
/users/creanj/.julia/v0.4/PumiInterface/test/pdepumiinterface.jl:142
 in facts at /users/creanj/.julia/v0.4/FactCheck/src/FactCheck.jl:315
 in include at ./boot.jl:253
 in include_from_node1 at ./loading.jl:133
 in include at ./boot.jl:253
 in include_from_node1 at loading.jl:133
 in process_options at ./client.jl:312
 in _start at ./client.jl:412


Why does  isapprox(::SubString{ASCIIString}, ::SubString{ASCIIString}) not 
match the fallback I defined?
Here is a minimal example (although it generates a slightly different error:
 MethodError: `isapprox` has no method matching isapprox(::ASCIIString, 
::ASCIIString)
): 

using FactCheck

import Base.isapprox

function isapprox(a, b)
  return a == b
end

facts("----- A non working example -----") do

  a = [1.5, "abc"]
  @fact a => roughly(a, atol=1e-14)
end


  Jared Crean