HeaderREPLs.jl is a Julia package that allows you to extend Julia's amazing REPL
to support "mini-applications" that need to communicate more information to the user.
They allow you to define a custom "header" type that you can use to print extra
information above the prompt.
To demonstrate, here we build a
CountingHeader type and show how the header is printed:
mutable struct CountingHeader <: AbstractHeader # note must be mutable and contain nlines field n::Int # internal data needed by the header nlines::Int # the number of lines needed for display---update this in print_header end function HeaderREPLs.print_header(io::IO, header::CountingHeader) if header.nlines == 0 if header.n > 0 printstyled(io, "Header:\n"; color=:light_magenta) for i = 1:header.n printstyled(io, " ", i, '\n'; color=:light_blue) end end header.nlines = nlines(header.n) end return nothing end
test/runtests.jl there is a complete example showing how you initialize this
mode and specify the user interaction: briefly, a pipe character ('|') switches into
"count" mode, and once in "count" mode '+' and '-' increment and decrement
Here, let's check out the outcome with a series of images.
This is what you see when you first press '|'.
n starts at 0, and our
print_header method above displays nothing in that case.
This is what you get after pressing '+' three times.
Now after pressing '-'. Note the line moved up to stay aligned.
Note we can enter Julia commands as usual.
In this demo, "count" mode is non-sticky, so it reverts back to the
In theory at least, "count" mode works as you'd expect when you traverse the history: when you get to a "count" line it shows the (current) header.
The package exports a few utilities that may make it easier to define custom REPL modes.
Aside from key-binding initialization utilities (see the source for details),
perhaps the two most useful are
? for more information.
Currently this package overwrites a few methods in Julia's "REPL" standard library. This generates some warnings. Hopefully we can eliminate them in a future version of this package.