# \[ANN\] WildcardArrays.jl

**URL:** https://discourse.julialang.org/t/ann-wildcardarrays-jl/112693
**Category:** Package Announcements
**Tags:** announcement, arrays, sparsearrays
**Created:** [April 8, 2024, 7:11pm UTC](https://discourse.julialang.org/t/ann-wildcardarrays-jl/112693 "2024-04-08T19:11:17Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![licioromao](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/licioromao/32/208349_2.png) [@licioromao](https://discourse.julialang.org/u/licioromao)
#### Post date: [April 8, 2024, 7:11pm UTC](https://discourse.julialang.org/t/ann-wildcardarrays-jl/112693/1 "2024-04-08T19:11:17Z")

</div>

Hi all,

I would like to share with you the package [WildcardArrays.jl](https://github.com/sisl/WildcardArrays.jl). It allows us to specify sparse matrices from text files; repeated entries can be specified using a wildcard character (’\*’). Version 0.1.0 API is described in the README file as part of the above github repository. Below is a minimal example that illustrates the current functionality:

```julia
using WildcardArrays

A = """ : * : * 
1 2 
1 2. 
3 8. 
1 90000 
2. 2 
1 10 """ 

dim1 = 4 
dim2 = 2 
dim3 = 6 
dim4 = 2 

wA = WildcardArray(A, [dim1,dim2,dim3,dim4]) 
wA[1,1,1,1] # This should be equal to one 
wA[4,2,4,2] # This should be equal to 90000

```

The inspiration for this package arouse during our attempt to parse POMDPs described using the file format described in [POMDP File Format](http://pomdp.org/code/pomdp-file-spec.html) into the [POMDPs.jl](https://github.com/JuliaPOMDP/POMDPs.jl) Julia framework.

We believe that the WilcardArray data structure is general enough, with potential to be used in several applications, so we decide to wrap its functionalities within WildcardArrays.jl and share with the Julia community. Of course, any feedback is greatly appreciated!