mtac
Reverse the order of an array
mtac
takes input from stdin and reverses the order of
it.
It’s name is derived from a program called tac
- a tool
that functions like cat
but returns the contents in the
reverse order. The difference with the mtac
builtin is that
it is data-type aware. So it doesn’t just function as a replacement for
tac
but it also works on JSON arrays, s-expressions, and
any other data-type supporting arrays compiled into Murex.
<stdin> -> mtac -> <stdout>
» ja [Monday..Friday] -> mtac
[
"Friday",
"Thursday",
"Wednesday",
"Tuesday",
"Monday"
]
# Normal output (without mtac)
» ja [Monday..Friday]
[
"Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday"
]
Please bare in mind that while Murex is optimised with concurrency
and streaming in mind, it’s impossible to reverse an incomplete array.
Thus all all of stdin must have been read and that file closed before
mtac
can output.
In practical terms you shouldn’t notice any difference except for when stdin is a long running process or non-standard stream (eg network pipe).
mtac
list.reverse
prefix
:
Prefix a string to every item in a listsuffix
:
Prefix a string to every item in a listappend
: Add data to the end of an arrayprepend
: Add data to the start of an arraymsort
:
Sorts an array - data type agnosticcount
: Count
items in a map, list or array2darray
: Create a 2D JSON array from multiple input
sourcesja
:
A sophisticated yet simply way to build a JSON arraymap
:
Creates a map from two data sourcesta
: A
sophisticated yet simple way to build an array of a user defined
data-typea
: A sophisticated yet simple way to stream an array or
list (mkarray)pretty
: Prettifies data documents to make it human
readablejsplit
: Splits stdin into a JSON array based on a regex
parameterThis document was generated from builtins/core/lists/mtac_doc.yaml.
This site's content is rebuilt automatically from murex's source code after each merge to the master
branch. Downloadable murex binaries are also built with the website.
Last built on Sat Aug 23 22:28:13 UTC 2025 against commit ad23f13ad23f131bfecd82ea8a12d9b3e92aab5d8398ae9.
Current version is 7.0.2129 (website) which has been verified against tests cases.