[julia-users] scope of the expression (made with Expr)
Hi, just a quick question on the scope/environment of an expression. I am using the Expr construct inside a function to create an expression, and I would then want to use this expression in various different places. Here's a short example First we have a simple function funky that takes in a function ff, and applies it to two symbolic arguments :x and :y julia function funky(ff::Function) Expr(:call, ff, :x, :y) end funky (generic function with 1 method) We define x and y to be 1 and 2 respectively julia x,y = 1,2 (1,2) No surprise here, when funky is passed with the function +, it adds x and y together julia eval(funky(+)) 3 However, now I want to use this expression with different bindings for x and y, I attempt the following julia function funfun(x, y) eval(funky(+)) end funfun (generic function with 1 method) Which doesn't seem to work. Here the result is sitll 3, presumably it is using the earlier bindings of x=1, y=2 julia funfun(4,5) 3 I would really liked the last result to be 9. So far it seems the expression uses static scoping and it's looking up the binding for :x and :y in the frame generated by calling funky, and not finding it there, it looks up :x and :y in the global frame, which is 1 and 2. Is there a way to bind the symbols in an expression to different things? is there like an environment dictionary where we can mess with, or is there some clean way of doing it? Much much much appreciated!!! --evan
[julia-users] how do I overwrite the toString equivalent in Julia?
I have a type with a lot of fields, but when I want to print it I only want to output the name field of that type. So when I print an array of objects of this type, I get a on the prinout an array of names instead of a huge clutter of prints. how might I do that? much thanks!!
[julia-users] pair-wise operation on an array?
say I want to compute a pair-wise diff for all the elements in the array. input:[1, 2, 4, 7, 8] output:[1, 2, 3, 1] is there some kind of beautiful way of doing it? i.e. w/o using a for loop nor using explicit indecies
Re: [julia-users] pair-wise operation on an array?
i see, maybe my example is too special. What i meant is I have an array of elements and I have a binary operator which I want to apply to every adjacent elements. On Saturday, February 7, 2015 at 7:26:55 AM UTC-5, Tamas Papp wrote: diff([1, 2, 4, 7, 8]) I don't think it gets more beautiful than this :D Best, Tamas On Sat, Feb 07 2015, Evan Pu evanth...@gmail.com javascript: wrote: say I want to compute a pair-wise diff for all the elements in the array. input:[1, 2, 4, 7, 8] output:[1, 2, 3, 1] is there some kind of beautiful way of doing it? i.e. w/o using a for loop nor using explicit indecies
[julia-users] incomplete println? (and debugging memory in general)
I'm trying to find a memory bug where all of a sudden my program freezes and eats up all the memory. I tried to do some printing, and tried to understand which line of code is responsible for causing the memory leak to happen. The print statement looks like this: println(computing cost for..., fact.f_name, , dom) where fact is an object with a name, f_name, which is a string, and dom is simply a list of tuple of numbers. Usually, this line of code will output something like this in the console: computing cost for...f_inte1 [(7.2109375,7.21875)] Indicating that it is about to start computing the cost for the fact object. However, when this memory bug occurs, it only prints this: computing cost for...^CERROR: interrupt It does not give me the name of fact before the bug happens, nor does it attempt to print out the dom. It doesn't even give me a stack trace! I am very clueless on what could be happening. So here is my 3 questions: 1) What could cause a print statement to not finish printing? the fact objects are all already allocated, and all with a valid f_name field. 2) If there is some memory error where I am forced to ^C before my computer freezes, how can I recover a call-stack? the answer here I think... is I am using the @profile macro so something happened that prevented the call-stack from showing. 3) Is there some way of knowing which part of the program is consuming most of the memory at the time of the bug? I tried using --track-allocation=all, but I do not care about memories that are already re-claimed by the garbage collector, but I do care about memory yet to be claimed at the time of the error. Sorry for the long post... --evan
[julia-users] julia array type?
I'm trying to construct an array while making an array of pairs of floats.
The error below is extremely confusing and I have no idea why.
=
# create the array w/o type declarations works fine
julia x = [(0.0, 1.0), (0.0, 1.0)]
2-element Array{(Float64,Float64),1}:
(0.0,1.0)
(0.0,1.0)
# but declaring the type in the constructor breaks it?!
julia y = (Float64, Float64)[(0.0, 1.0), (0.0, 1.0)]
ERROR: `getindex` has no method matching
getindex(::Type{(Float64,Float64)}, ::(Float64,Float64),
::(Float64,Float64))
# but somehow manually adding with push! works?!
julia z = (Float64, Float64)[]
0-element Array{(Float64,Float64),1}
julia push!(z, (0.0, 1.0))
1-element Array{(Float64,Float64),1}:
(0.0,1.0)
julia push!(z, (0.0, 1.0))
2-element Array{(Float64,Float64),1}:
(0.0,1.0)
(0.0,1.0)
[julia-users] Re: What's your favourite editor?
light table juno plugin. literally cannot use the language w/o it haha, although it is buggy at times On Saturday, January 17, 2015 at 11:34:46 AM UTC-5, Terry Seaward wrote: Hi, Just curious to know what people use to write/edit their Julia code (os/app)?
[julia-users] Re: Simple type constructor question
very handy, just saw this reply now. thanks a ton On Thursday, November 6, 2014 at 5:16:31 PM UTC-5, Valentin Churavy wrote: You could using a abstract type instead of a Union abstract Element type Tree body :: Element end type Branch : Element a :: Tree b :: Tree end type Leaf : Element a end so this would create a tree julia Tree(Branch( Tree(Leaf(:a)), Tree(Branch( Tree(Leaf(:b)), Tree(Leaf(:c)) )) )) Tree(Branch(Tree(Leaf(:a)),Tree(Branch(Tree(Leaf(:b)),Tree(Leaf(:c)) adding the following methods makes it a bit more readable Tree(a :: Any) = Tree(Leaf(a)) Tree(a :: Tree,b::Tree) = Tree(Branch(a, b)) julia Tree( Tree(:a), Tree( Tree(:b), Tree(:c) ) ) Tree(Branch(Tree(Leaf(:a)),Tree(Branch(Tree(Leaf(:b)),Tree(Leaf(:c)) So this stills looks a bit clunky and you should also be aware that this allows for Tree(Tree(:a), Tree(1.0)) so some type constraints would be in order. On Thursday, 6 November 2014 21:52:05 UTC+1, Evan Pu wrote: Quick question: In haskell one can do something like the following to define a type: data Tree a = Branch (Tree a) (Tree a) | Leaf a Is there something analogous in the Julia world? I'm sure I'm doing something wrong here... julia type Tree body :: Union(Branch, Leaf) end ERROR: Branch not defined julia type Branch a :: Tree b :: Tree end ERROR: Tree not defined julia type Leaf a end thanks!
[julia-users] what do you do with strings in julia
what is the convention? I kept getting
`convert` has no method matching convert(::Type{SubString(UTF8String)}},
::ASCIIString)
all the time, every time
I I don't really know _why_ this error comes up, or how or what. I just
kept typing :: ASCIIString trying to force the types onto things and
hopefully it goes away, so of course I'm doing something wrong.
thanks~
[julia-users] Re: what do you do with strings in julia
Steven,
The error is actually an issue with LightTable's Juno plugin and actually
has nothing to do with Julia.
I think what happened is in reporting the errors the plugin makes some
mistake and ended up reporting another error(or itself had some misuse of
strings) instead.
The actual error was discovered while running it from the command shell is
in fact:
ERROR: assertion failed
in ∫ at SimplePoly.jl:286
in ∫ at SimplePoly.jl:518
in ∫ at SimplePoly.jl:786
in ∫ at Factor.jl:153
which seems more reasonable, as the assertion is the one I wrote.
sorry for the troubles!
On Tuesday, January 13, 2015 at 3:16:44 PM UTC-5, Steven G. Johnson wrote:
Though we could define such a conversion method with:
convert{T:AbstractString}(::Type{SubString{T}}, s::AbstractString) =
let s′ = T(s); SubString(s′, 1, endof(s′)); end
Evan, what is your application here? What are you trying to do?
[julia-users] Re: what do you do with strings in julia
I'll try. the call chain is rather large and I'll see if I can get it down to a few constructs. On Tuesday, January 13, 2015 at 4:34:39 PM UTC-5, Steven G. Johnson wrote: On Tuesday, January 13, 2015 at 4:10:54 PM UTC-5, Evan Pu wrote: Steven, The error is actually an issue with LightTable's Juno plugin and actually has nothing to do with Julia. Can you file an issue at: https://github.com/one-more-minute/Jewel.jl explaining how the error arose?
[julia-users] initialize array of arrays?
Imagine I want to initialize an array of array.
x = [[1,2],[3,4]]
but this gets flattened into [1,2,3,4]
Is there an easy way of constructing a nested array? I'm currently having
to do
x = Array{Int64}[]
push!(x, [1,2])
push!(x, [3,4])
which doesn't seem very clean
[julia-users] Re: initialize array of arrays?
works for me! thanks!!
On Thursday, January 8, 2015 1:07:35 PM UTC-5, Steven G. Johnson wrote:
You can do Array{Int}[[1,2],[3,4]], or Vector{Int}[[1,2],[3,4]] if you
want to restrict the entries to be 1d arrays of Int.
Re: [julia-users] Re: package proposal
is this thread still alive? a phc package would be good... On Monday, June 23, 2014 5:26:34 AM UTC-7, Andrei Berceanu wrote: By the way I recently stumbled upon NLSolve.jl, and asked them if they would be interested in PHCpack https://github.com/EconForge/NLsolve.jl/issues/12 Still no reply on their part yet though. On Monday, June 23, 2014 1:06:03 PM UTC+2, Andrei Berceanu wrote: Free binary versions for Mac and Windows of the gnu-ada compiler are available at http://libre.adacore.com/ and are very easy to install. As for HOMPACK, the main difference is that PHCpack is specifically targeted for polynomial systems. HOMPACK provides continuation methods for general nonlinear systems and has extra drivers for polynomial systems. Another main difference is that PHCpack offers polyhedral homotopies, which are absent from HOMPACK. So I guess it depends on what we want really, personally I am interested in polynomial systems. Please let me know if you succeed in installing the ada compiler for Mac from the above link. On Friday, June 20, 2014 11:36:01 PM UTC+2, Tony Kelman wrote: That sounds like the best plan for the PHCpack code. Have you looked at or are you familiar with whether HOMPACK as Hans mentioned would be able to provide similar functionality? I say that just because more of us are used to building Fortran code than Ada. Ada should be reasonable to work with on Linux, and maybe even in MinGW or Cygwin, but it doesn't look like it's set up in Homebrew for Mac users. If you know of a standard way to install GNAT and can get the library building on at least your platform of choice, go for it. On Friday, June 20, 2014 2:14:18 PM UTC-7, Andrei Berceanu wrote: I have contacted the author ( https://github.com/janverschelde/PHCpack/issues/3) and it seems redistribution under a different license is not really an option. However, if what Milan says is correct, then we should be able to include it 'as-is'. Now for the interface, I was thinking that, since there already exists a comprehensive C API to the Ada code, we could call that from Julia, what do you guys reckon? On Friday, June 6, 2014 2:18:33 PM UTC+2, Milan Bouchet-Valat wrote: Le vendredi 06 juin 2014 à 03:43 -0700, Hans W Borchers a écrit : Please notice that PHCpack is distributed under GPL license, so your first step should be to contact the author and ask for his approval to distribute it under a lesser license such as MIT. Though since it's a package rather than code to be included in Julia Base, GPL is fine too. Regards
[julia-users] how to test NaN in an array?
1 in [1,2,3] # returns true NaN in [NaN, 1.0, 2.0] # returns false how do I test if a float64 NaN is present in an array? I'm doing some numerical computation and it can have some NaN error, I want to drop the arrays that has NaN.
Re: [julia-users] how to test NaN in an array?
come to think of it that is the right semantics. well designed language this is! On Monday, December 15, 2014 3:35:22 PM UTC-5, John Myles White wrote: You need to check isnan() per element. NaN == NaN is false, so in() fails on NaN right now. -- John On Dec 15, 2014, at 3:33 PM, Evan Pu evanth...@gmail.com javascript: wrote: 1 in [1,2,3] # returns true NaN in [NaN, 1.0, 2.0] # returns false how do I test if a float64 NaN is present in an array? I'm doing some numerical computation and it can have some NaN error, I want to drop the arrays that has NaN.
[julia-users] customized hash function (or equality function)?
Hi, this should be a simple affair.
I have a polynomial object that keeps track of its coefficients, it is
defined as follows:
immutable Poly1
coef :: Array{Float64}
end
I would like to make a dictionary with keys that are Poly1 type, like
follows:
# creation
r_dict1 = [Poly1([1.0, 2.0]) = 1]
# access
r_dict1[Poly1([1.0, 2.0])]
However currently it gives the arrow key not found
By looking at the hash we can see why, the has is not identical even for
equal polynomials:
hash(Poly1([1.0, 2.0])) # gives an arbitrary hex string
hash(Poly1([1.0, 2.0])) # gives a different hex string
How would I implement my own hash so the same polynomials (by same I mean
the coefficients are same, i.e. the coef::Array{Float64} part of the two
polynomials are the same?
Much thanks!!
--evan
[julia-users] Re: customized hash function (or equality function)?
wonderful! thanks!! On Wednesday, December 10, 2014 8:24:17 PM UTC-5, Steven G. Johnson wrote: Base.hash(p::Poly1, h::Uint) = hash(p.coef, h) Base.(==)(p1::Poly1, p2::Poly2) = p1.coef == p2.coef (If you override hash you should always override == to be consistent, and vice versa.)
[julia-users] Simple type constructor question
Quick question: In haskell one can do something like the following to define a type: data Tree a = Branch (Tree a) (Tree a) | Leaf a Is there something analogous in the Julia world? I'm sure I'm doing something wrong here... julia type Tree body :: Union(Branch, Leaf) end ERROR: Branch not defined julia type Branch a :: Tree b :: Tree end ERROR: Tree not defined julia type Leaf a end thanks!
Re: [julia-users] type confusions in list comprehensions (and how to work around it?)
It does indeed happens inside the function, if you pass a function as an
argument to it (rather than refering to f implicitly in the function body,
you explicitly pass in f as an extra argument)
see below:
julia f(x) = x + 1
f (generic function with 1 method)
julia g(f, xs) = [f(x) for x in xs]
g (generic function with 1 method)
julia xs = [1,2,3]
3-element Array{Int64,1}:
1
2
3
julia g(f,xs)
3-element Array{Any,1}:
2
3
4
On Tuesday, November 4, 2014 2:22:24 AM UTC-5, Jutho wrote:
This only happens in global scope, not inside a function? If you define
f(list) = return [g(x) for x in list]
then f(xs) will return an Array{Float64,1}.
Op dinsdag 4 november 2014 03:23:36 UTC+1 schreef K leo:
I found that I often have to force this conversion, which is not too
difficult. The question why comprehension has to build with type Any?
On 2014年11月04日 07:06, Miguel Bazdresch wrote:
How could I force the type of gxs1 to be of an array of Float64?
The simplest way is:
gxs1 = Float64[g(x) for x in xs]
-- mb
On Mon, Nov 3, 2014 at 6:01 PM, Evan Pu evanth...@gmail.com
mailto:evanth...@gmail.com wrote:
Consider the following interaction:
julia g(x) = 1 / (1 + x)
g (generic function with 1 method)
julia typeof(g(1.0))
Float64
julia xs = [1.0, 2.0, 3.0, 4.0]
4-element Array{Float64,1}:
1.0
2.0
3.0
4.0
julia gxs1 = [g(x) for x in xs]
4-element Array{Any,1}:
0.5
0.33
0.25
0.2
Why isn't gxs1 type of Array{Float64,1}?
How could I force the type of gxs1 to be of an array of Float64?
julia gxs2 = [convert(Float64,g(x)) for x in xs]
4-element Array{Any,1}:
0.5
0.33
0.25
0.2
somehow this doesn't seem to work...
[julia-users] Is there an implicit apply method for a type?
Hello, I want to create a polynomial type, parametrized by its coefficients, able to perform polynomial additions and such. but I would also like to use it like a function call, since a polynomial should be just like a function Something of the following would be nice: p = Poly([1,2,3]) # creating a polynomial p(x) = 1 + 2x + 3x^2 q = Poly([1,2]) # creating a polynomial 1 + 2x r = p + q # using dynamic dispatch, creating the polynomial 2 + 4x + 3x^2 r(1) # this should give 9, by evaluating polynomial r at x = 1 Is there something in Julia that would allow me to create what I have in mind? thanks!!
[julia-users] base case for the reduce operator?
Hi I'm writing a simple polynomial module which requires addition of polynomials. I have defined the addition by overloading the function + with an additional method: +(p1::Poly, p2::Poly) = ...# code for the addition I would like to use + now in a reduce call, imagine I have a list of polynomials [p1, p2, p3], calling reduce(+, [p1, p2, p3]) behaves as expected, giving me a polynomial that's the sum of the 3 however, I would also like to cover the edge cases where there's only a single polynomial or no polynomial. I would like the following behaviours, : # reducing with a single polynomial list gives just the polynomial back reduce(+, [p1]) p1 # reducing with an empty list gives back the 0 polynomial reduce(+, []) ZeroPoly How might I add such functionality? For the empty list case, how might I annotate the type so Julia is aware that [] means an empty list of polynomials rather than an empty list of Any?
Re: [julia-users] Fully Typed Function As Argument Type
Nooo TT I was looking for it too today. Hope it gets added soon, fingers crossed! On Thursday, August 14, 2014 10:31:17 AM UTC-4, John Myles White wrote: Not possible in the current versions of Julia. Maybe one day. There are bunch of us who’d like to have this functionality, but it’s a non-trivial addition of complexity to the compiler. — John On Aug 14, 2014, at 4:59 AM, Chris Kellendonk chriske...@gmail.com javascript: wrote: I'm new to the language so I may have missed something. But is there a way to make sure a function passed as an argument is of a specific type including it's arguments? It doesn't look like from the design of the language this could be supported but I'm curious. For example I would like to be able to do: function callme(handler::Function(Int32, Float64)) handler(12, 0.2) end And the compiler would guarantee the correct type of function is called. Thanks,
[julia-users] type confusions in list comprehensions (and how to work around it?)
Consider the following interaction:
julia g(x) = 1 / (1 + x)
g (generic function with 1 method)
julia typeof(g(1.0))
Float64
julia xs = [1.0, 2.0, 3.0, 4.0]
4-element Array{Float64,1}:
1.0
2.0
3.0
4.0
julia gxs1 = [g(x) for x in xs]
4-element Array{Any,1}:
0.5
0.33
0.25
0.2
Why isn't gxs1 type of Array{Float64,1}?
How could I force the type of gxs1 to be of an array of Float64?
julia gxs2 = [convert(Float64,g(x)) for x in xs]
4-element Array{Any,1}:
0.5
0.33
0.25
0.2
somehow this doesn't seem to work...
[julia-users] how to find out how many argument a function has?
I'm assuming the function only has a single method, although a more general answer would be nice too. Imagine I have: f(x,y,z) = x + y + z I would like to have something like num_args(f) which should give back 3 is there something that could let me do this? thanks a lot!!
[julia-users] how to i get number of arguments of a function?
How do I get the number of arguments of a function? for instance, f(x, y) = x + y I want something like num_args(f), which will give me back 2. If the function has multiple methods then something more general would be nice, but so far I only care about functions with just a single method. Is there something like this? thanks alot!!
Re: [julia-users] how to i get number of arguments of a function?
thanks!! On Thursday, October 16, 2014 12:41:22 PM UTC-4, Tim Holy wrote: You might want to look into the various introspection functions, like `methods`, `code_lowered`, etc. Leah Hanson had a nice blog post: http://blog.leahhanson.us/julia-introspects.html For your specific problem, once you have a specific method, then `m.sig` returns its signature, and you can just compute the length. A MethodTable (returned by `methods(sum)`, for example) is iterable, so you can iterate over the table until you find what you want. Best, --Tim On Thursday, October 16, 2014 08:55:01 AM Evan Pu wrote: How do I get the number of arguments of a function? for instance, f(x, y) = x + y I want something like num_args(f), which will give me back 2. If the function has multiple methods then something more general would be nice, but so far I only care about functions with just a single method. Is there something like this? thanks alot!!
[julia-users] named function within a loop is overwritten?
Consider this code: function give_funs() funs = [] for i in 1:5 function newfun() i end funs = [funs, newfun] end funs end The intention is to create 5 functions and store them in a list called funs. All the functions take no argument, and when the ith function is called, it returns i. However, when run... funs1 = give_funs() funs1[1]() # this should give 1, but instead it gives 5 funs1[2]() # this should give 2, but instead it gives 5 as well This is problem goes away if I stop naming the function as newfun but instead use ananymous functions like so: funs = [funs, () - i] however in real code I would like to give it a name so to be more clear what the function is suppose to compute It seems that these functions are bound by their function names, and since they're all named newfun, the compiler over-write the old ones defined earlier. How should this be resolved?
Re: [julia-users] how to i get number of arguments of a function?
yeah, the function I'm intending to inspect will be defined by me and they shouldn't be varargs On Thursday, October 16, 2014 2:10:34 PM UTC-4, Toivo Henningsson wrote: Though you should probably look out for varargs methods too, the length of e.g. (Int...) is one, but a method with that signature can take any number of arguments.
