Cheat sheet

Short examples of how Faber is actually written. Every snippet on these pages compiles — they are checked against the compiler on each build, not typed from memory.

This is not the corpus. The corpus is the exhaustive reference: one page per keyword, every construct registered and measured. The cheat sheet is the opposite shape — a handful of pages, each showing the two or three ways people really write something.

The feel of the language#

Three signals do most of the work. Types come before names, behaviour words are Latin, and structure is carried by glyphs rather than punctuation soup.

reader locale

faber format --locale en — English reader surface

fn divide(int a, int b) → int ∪ null {
    if b ≡ 0 then return null
    return a / b
}

faber format --locale la — canonical Faber

functio divide(numerus a, numerus b) → numerus ∪ nihil {
    si b ≡ 0 ergo redde nihil
    redde a / b
}

faber format --locale th-TH — Thai

ฟังก์ชัน divide(จำนวน a, จำนวน b) → จำนวน ∪ ว่าง {
    ถ้า b ≡ 0 ดังนั้น คืน ว่าง
    คืน a / b
}

faber format --locale zh-Hans — Simplified Chinese

函数 divide(整数 a, 整数 b) → 整数 ∪ 空 {
    如果 b ≡ 0 则 返回 空
    返回 a / b
}

faber format --locale zh-Hant — Traditional Chinese

函式 divide(整數 a, 整數 b) → 整數 ∪ 空 {
    若 b ≡ 0 則 傳回 空
    傳回 a / b
}

faber format --locale vi — Vietnamese

hàm divide(số a, số b) → số ∪ rỗng {
    nếu b ≡ 0 do_đó trả rỗng
    trả a / b
}

faber format --locale ar — Arabic

دالة divide(عدد a, عدد b) → عدد ∪ لاشيء {
    إذا b ≡ 0 إذن أعد لاشيء
    أعد a / b
}

faber format --locale hi — Hindi

फलन divide(संख्या a, संख्या b) → संख्या ∪ शून्य {
    यदि b ≡ 0 अतः लौटाओ शून्य
    लौटाओ a / b
}

numerus a — type first, then the name. → introduces the return type. ∪ joins types into a union, so this returns a number or nothing. ≡ is equality. return returns.

A whole program, doing real work:

reader locale

faber format --locale en — English reader surface

main {
    const list<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    const tensor<f32, []> seed ← vacua
    const tensor<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    const f32 medium ← matrix.media()
    print medium
}

faber format --locale la — canonical Faber

incipit {
    fixum lista<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    fixum tensor<f32, []> seed ← vacua
    fixum tensor<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    fixum f32 medium ← matrix.media()
    nota medium
}

faber format --locale th-TH — Thai

เริ่ม {
    คงที่ รายการ<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    คงที่ เทนเซอร์<f32, []> seed ← เซตว่าง
    คงที่ เทนเซอร์<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    คงที่ f32 medium ← matrix.media()
    บันทึก medium
}

faber format --locale zh-Hans — Simplified Chinese

入口 {
    常量 列表<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    常量 张量<f32, []> seed ← 空集
    常量 张量<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    常量 f32 medium ← matrix.media()
    显示 medium
}

faber format --locale zh-Hant — Traditional Chinese

入口 {
    定值 列表<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    定值 張量<f32, []> seed ← 空集
    定值 張量<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    定值 f32 medium ← matrix.media()
    註記 medium
}

faber format --locale vi — Vietnamese

bắt_đầu {
    hằng danh_sách<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    hằng ten_xo<f32, []> seed ← tập_rỗng
    hằng ten_xo<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    hằng f32 medium ← matrix.media()
    ghi_chú medium
}

faber format --locale ar — Arabic

بداية {
    ثابت قائمة<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    ثابت موتر<f32, []> seed ← فارغ
    ثابت موتر<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    ثابت f32 medium ← matrix.media()
    اعرض medium
}

faber format --locale hi — Hindi

आरंभ {
    स्थिर सूची<f32> valores ← [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
    स्थिर टेंसर<f32, []> seed ← खाली
    स्थिर टेंसर<f32, [2, 3]> matrix ← seed.strue(valores, [2, 3])
    स्थिर f32 medium ← matrix.media()
    दिखाओ medium
}

main is the entry point. const binds a constant. ← is the bind glyph — assignment reads right-to-left into the name. print prints.

By topic#

Page	What it covers
Entry points	`main`, async entry, CLI arguments and annotations
Bindings	`const` vs `var`, type holes, union holes
Types and widths	Numbers and their widths, lists, tables, tensors, vectors, and the sugar for each
Generics	Generic functions, generic containers, `class`
Loops	`for` over values, keys, and ranges; `while`
Control flow	`if` / `elif` / `else`, `switch`, `match` over unions
Errors and catching	The `⇥` error channel, `iace`, and `catch` on many block forms
Conversions	`↦` conversion, recovery with `⇥`, conversion vs casting
Imports	Standard library, local files, aliasing, `publica` vs `privata`
Reader locales	The same program in eight human languages, side by side
Testing	`probandum`, `proba`, `adfirma`, tags, running tests
Commands	The daily `faber` CLI loop

Keywords you will meet first#

The twenty that carry most Faber source. Each links to the page that shows it in use; the corpus has the exhaustive entry for every one.

Keyword	Means	Shown on
`main`	Program entry point	Entry points
`incipiet`	Async program entry point	Entry points
`fn`	Declare a function	Generics
`return`	Return a value	Control flow
`const`	Bind a constant	Bindings
`var`	Bind a mutable variable	Bindings
`class`	Declare a record type	Generics
`typus`	Name an alias for a type	Types and widths
`if`	If	Control flow
`elif`	Else-if	Control flow
`else`	Else	Control flow
`switch`	Select over a value	Control flow
`match`	Match over a union	Control flow
`case`	A case arm	Control flow
`for`	Iterate	Loops
`while`	While	Loops
`iace`	Send a value down the error channel	Errors and catching
`catch`	Catch from the error channel	Errors and catching
`import`	Import a module or item	Imports
`proba`	Declare a test	Testing

Glyphs#

Glyph	Reads as
`←`	bind — put the value on the right into the name on the left
`→`	returns this type
`⇥`	…and may fail with this error type
`≡`	equals
`∪`	union of types
`↦`	convert to this type
`∴`	closure joint
`‥`	range, as in `0‥10`

Full discussion: Glyphs and Latin.