Declares a named function or method.
Aliases: function
Syntax: functio <name>(<params>) [modifiers] [→ <type>] [⇥ <error-type>] <block>
Category
function
Related
Examples
examples/corpus/functio/functio.fab (canonical · keyword)
Declares a named function or method.
# Basic function declarations
#
# functio <nomen>() { <body> }
# functio <nomen>() → <type> { <body> }
#
# GRAMMAR:
# funcDecl :← 'functio' ident '(' paramList ')' ('→' type)? block
#
# EXPECTED OUTPUT:
# functio.expected — four diagnostics (greetings, name, integer).
# Function with no parameters, no return
functio saluta() {
nota "Salve, Mundus!"
}
# Function with parameter, no explicit return type
functio dic(textus verbum) {
nota verbum
}
# Function with return type
functio nomen() → textus {
redde "Marcus Aurelius"
}
# Function with parameter and return type
functio duplica(numerus n) → numerus {
redde n * 2
}
incipit {
saluta()
dic("Bonum diem!")
fixum _ rex ← nomen()
nota rex
nota duplica(21)
}Expected output:
Salve, Mundus!
Bonum diem!
Marcus Aurelius
42examples/corpus/functio/in-ex.fab (canonical · keyword)
Declares a named function or method.
# Parameter borrow markers: de (shared), in (mutable), ex (consume)
#
# de <type> <nomen> -- shared borrow (read-only from caller's view)
# in <type> <nomen> -- mutable borrow (callee may modify the binding)
# ex <type> <nomen> -- consume/move ownership into callee
#
# GRAMMAR:
# parameter :← ('de' | 'in' | 'ex')? type ident ...
#
# EXPECTED OUTPUT:
# mutabile
# 6
# salve
#
# BACKEND: Rust lowering treats `in` as immutable args (borrow lowering gap;
# whitelist: functio/in-ex.fab). Go target is runnable.
# --- Shared borrow: read label without taking ownership ---
functio imprime(de textus label) → vacuum {
nota label
}
# --- Mutable borrow: double the caller's numerus in place ---
functio duplica(in numerus value) → vacuum {
value ← value * 2
nota value
}
# --- Consume: take ownership of textus and return it ---
functio consume(ex textus buffer) → textus {
redde buffer
}
incipit {
imprime("mutabile")
varia numerus valor ← 3
# in borrows valor mutably inside duplica
duplica(valor)
# ex moves the literal into consume
nota consume("salve")
}Expected output:
mutabile
6
salve
examples/corpus/functio/recursio.fab (canonical · keyword)
Declares a named function or method.
# Recursive functions
#
# A function may call itself; every recursion path needs a base case.
#
# GRAMMAR:
# funcDecl with callExpr naming the enclosing function
#
# EXPECTED OUTPUT:
# factorial: 1, 1, 120, 3628800
# fibonacci: 0, 1, 55
# summatio: 15, 55
# Factorial: n! ← n * (n-1)!
functio factorial(numerus n) → numerus {
si n ≤ 1 {
# base case
redde 1
}
redde n * factorial(n - 1)
}
# Fibonacci: fib(n) ← fib(n-1) + fib(n-2)
functio fibonacci(numerus n) → numerus {
si n ≤ 0 {
redde 0
}
si n ≡ 1 {
redde 1
}
redde fibonacci(n - 1) + fibonacci(n - 2)
}
# Sum from 1 to n
functio summatio(numerus n) → numerus {
si n ≤ 0 {
redde 0
}
redde n + summatio(n - 1)
}
incipit {
# --- Factorial examples ---
nota factorial(0)
nota factorial(1)
nota factorial(5)
nota factorial(10)
# --- Fibonacci examples ---
nota fibonacci(0)
nota fibonacci(1)
nota fibonacci(10)
# --- Summation examples ---
nota summatio(5)
nota summatio(10)
}Expected output:
1
1
120
3628800
0
1
55
15
55
examples/corpus/functio/sponte-vel.fab (canonical · keyword)
Declares a named function or method.
# Parameters with sponte and vel
#
# sponte marks a voluntary (optional) parameter slot
# vel provides a default when the argument is omitted
#
# GRAMMAR:
# parameter :← (preposition)? type nomen sponte? ('ut' alias)? ('vel' defectum)?
#
# EXPECTED OUTPUT:
# Salve, Marcus!, Salve, Dominus Marcus!, pagina lines with defaults/overrides,
# codex length and metire results, civis summary strings
functio saluta(textus nomen, textus titulus sponte) → textus {
si titulus est nihil {
redde "Salve, §!"(nomen)
}
redde "Salve, § §!"(titulus, nomen)
}
functio pagina(numerus pagina sponte vel 1, numerus quantitas sponte vel 10) → textus {
redde "pagina § cum § rebus"(pagina, quantitas)
}
functio metire(textus fons, de numerus altitudo sponte) → numerus {
si altitudo est nihil {
# de = shared borrow of fons
redde fons.longitudo()
}
redde altitudo
}
functio civis(textus nomen, numerus aetas sponte vel 0, bivalens activus sponte vel verum) → textus {
redde "civis: §, aetas: §, activus: §"(nomen, aetas, activus)
}
incipit {
nota saluta("Marcus")
nota saluta("Marcus", "Dominus")
# both sponte params use vel defaults
nota pagina()
nota pagina(2, 25)
# quantitas defaults to 10
nota pagina(5)
nota metire("codex")
nota metire("codex", 5)
nota civis("Julia")
nota civis("Julia", 25)
nota civis("Julia", 25, falsum)
}examples/corpus/functio/typi-parametri.fab (canonical · keyword)
Declares a named function or method.
# Functions with typed parameters (type-first syntax)
#
# functio <nomen>(<type> <param>, ...) → <type> { <body> }
#
# GRAMMAR:
# funcDecl :← 'functio' ident '(' paramList ')' ('→' type)? block
#
# EXPECTED OUTPUT:
# 49, 300, "Julius habet 30 annos", falsum, verum, 5.0
# Single typed parameter
functio quadratum(numerus n) → numerus {
redde n * n
}
# Multiple typed parameters
functio adde(numerus a, numerus b) → numerus {
redde a + b
}
# Mixed types for string formatting
functio narra(textus nomen, numerus aetas) → textus {
redde "§ habet § annos"(nomen, aetas)
}
# Boolean parameter and return
functio nega(bivalens valor) → bivalens {
redde non valor
}
# fractus (floating-point) parameters
functio media(fractus a, fractus b) → fractus {
redde (a + b) / 2.0
}
incipit {
nota quadratum(7)
nota adde(100, 200)
nota narra("Julius", 30)
nota nega(verum)
nota nega(falsum)
nota media(3.0, 7.0)
}Expected output:
49
300
Julius habet 30 annos
falsum
verum
5.0