tpapp/autoaligns.jl

AutoAligns

This Julia package helps align text for printing with a monospace font, by keeping track of the maximum width of each column. It is useful for printing matrices, tables, and analogous structures, and in particular for writing methods for Base.print.

Installation

This package is not yet registered on Julia's METADATA.jl. To install it, you must use the usual procedure for unregistered packages:

Pkg.clone("git://github.com/tpapp/AutoAligns.jl.git")

Note that the minimum required version of Julia is 0.6.

Usage

Create an AutoAlign object, then use print to save values into it, which are strings or converted to strings. The AutoAlign object keeps track of the current column (which you can query with position, but that is rarely necessary), and you can also provide a default alignment, or specify it before printing, using the methods

print(aa::AutoAlign, xs...)
println(aa::AutoAlign, xs...)

where the latter starts a new line after saving the values. Both accept a keyword argument align, for specifying alternate alignent for the preceding arguments.

Alignment can be specified as follows:

1. an atom left, right, or center, or any other user extension which is a subtype of Alignment,

2. a vector of alignment specifiers: for positions outside the length of the vector, the last element is used,

3. a Dict of position => alignment pairs, where the position :default provides the alignment for items not in the Dict.

Example

julia> using AutoAligns

julia> aa = AutoAlign(align = Dict(1 => left, :default => right));

julia> for (i, r) in zip([1, 100, 10000], ["a", "bb", "ccc"])
           print(aa, r)
           for j in 1:5
               print(aa, "  ", i + j) # padding
           end
           println(aa)
       end

julia> print(STDOUT, aa)
a        2      3      4      5      6
bb     101    102    103    104    105
ccc  10001  10002  10003  10004  10005

Notes

Spaces or separators such as | are not treated in a special way, and therefore should be accounted for when specifying positions for alignment.

Printing an AutoAlign object to a stream pads the strings with spaces so as to achieve the desired alignment.

An AutoAlign object is not a subtype of IO, as it does not implement a write(::AutoAlign, x::UInt8) method. Unlike IOBuffer, printing does not delete the contents.

Custom alignment types can be defined as subtypes of Alignment, by implementing align_string.