AUNSHIFT / >@

(aunshift aref-expression expr1 expr2 ... exprN)
(aunshift foo expr)               ; push to the front of foo
(>@ foo expr)                     ; same as above, short form

The AUNSHIFT instruction has the short-form >@. The greater-than sign facing towards the @ symbol is meant to visually indicate that something is being added to the front of the array. The value(s) can be any valid back-end expressions.

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Examples

Here is the FELT source we are going to convert to PHP and javaScript:

(defvar items [])
(>@ items []) ; items now contains a nested array
(aunshift (items 0) "World")
(>@ (items 0) "Hello")
(defvar message (implode (@ items 0) " "))
(emit "That message says: " message "\n")

Now let's render the code as PHP and execute it to show it worked:

$items = array();
array_unshift($items, array());
array_unshift($items[0], "World");
array_unshift($items[0], "Hello");
$message = implode($items[0], " ");
echo "That message says: ", $message, "\n";

and when run through the PHP interpreter we get this output:

$ felt docex.felt -cw | php
That message says: Hello World
felt docex.felt -cw | php
That message says: Hello World

And finally for Node/javaScript, this being the modified code as javaScript has no "implode" function so we have to fake it:

(defvar items [])
(>@ items []) ; items now contains a nested array
(aunshift (items 0) "World")
(>@ (items 0) "Hello")
(defvar message (implode (@ items 0) " "))
(emit "That message says: " message "\n")
(defun implode (x) (return (x.join)))

The generated code from the above FELT source is:

felt docex.felt -as nodejscoder
var items = [];
items.unshift([]);
items[0].unshift("World");
items[0].unshift("Hello");
var message = implode(items[0], " ");
console.log("That message says: " + message + "\\n");
function implode(x)
{return x.join();}

$ felt docex.felt -as nodejscoder | node
That message says: Hello, World