We can declare a function like this:

def function = { atom1 atom2 ... atomN }

Example:

noc> def square = {dup *}
noc> 5 square
=> [25]
noc> zap
noc> def number = {6} # We define a constant
noc> number square
=> [36]

It’s like the substitution, when we called the declared function, in fact it give this:

noc> 5 dup *

We can also declare a function like this:

def (function) = { atom1 atom2 ... atomN }

It’s useful for have a better syntax to define operators.

Source: std/string.noc

def ($) = {
    ---
    Convert a string to a quote of chars
    (example)
    "abc" $ => ['a' 'b' 'c']
    ---
    chars
}

When we declare a function, the function is pushed in the env. And we can access to this env with the 'env' command:

noc> :env
square: [dup *],