## val
[](https://github.com/terror/val/releases/latest)
[](https://crates.io/crates/val)
[](https://github.com/terror/val/actions/workflows/ci.yaml)
[](https://docs.rs/val)
[](https://deps.rs/repo/github/terror/val)
**val** (e**val**) is a simple arbitrary precision calculator language built
on top of [**chumsky**](https://github.com/zesterer/chumsky) and
[**ariadne**](https://github.com/zesterer/ariadne).
<img width="1667" alt="Screenshot 2025-04-17 at 7 57 27 PM" src="https://github.com/user-attachments/assets/8977c82c-1e9f-413e-8f0d-7ce124f1ca66" />
## Installation
`val` should run on any system, including Linux, MacOS, and the BSDs.
The easiest way to install it is by using [cargo](https://doc.rust-lang.org/cargo/index.html),
the Rust package manager:
```bash
cargo install val
```
### Pre-built binaries
Pre-built binaries for Linux, MacOS, and Windows can be found on [the releases
page](https://github.com/terror/val/releases).
## Usage
The primary way to use **val** is via the provided command-line interface. There
is currently ongoing work on a Rust library and web playground, which will
provide a few extra ways to interact with the runtime.
Below is the output of `val --help`, which describes some of the
arguments/options we support:
```present cargo run -- --help
val 0.3.2
Liam <liam@scalzulli.com>
An arbitrary precision calculator language
Usage: val [OPTIONS] [FILENAME]
Arguments:
[FILENAME] File to evaluate
Options:
-e, --expression <EXPRESSION> Expression to evaluate
-p, --precision <PRECISION> Decimal precision to use for calculations [default: 1024]
-r, --rounding-mode <ROUNDING_MODE> Rounding mode to use for calculations [default: to-even]
-h, --help Print help
-V, --version Print version
```
Running **val** on its own will spawn a repl (read–eval–print loop) environment,
where you can evaluate arbitrary **val** code and see its output immediately. We
use [rustyline](https://github.com/kkawakam/rustyline) for its implementation,
and we support a few quality of life features:
- Syntax highlighting (see image above)
- Persistent command history
- Emacs-style editing support by default
- Filename completions
- Hints (virtual text pulled from history)
The **val** language supports not only expressions, but quite a few
[statements](https://github.com/terror/val/blob/ea0c163934ee3f4afe118384b1281d296f116539/src/ast.rs#L35) as well.
You may want to save **val** programs and execute them later, so
the command-line interface provides a way to evaluate entire files.
For instance, lets say you have the following **val** program at
`factorial.val`:
```rust
fn factorial(n) {
if (n <= 1) {
return 1
} else {
return n * factorial(n - 1)
}
}
println(factorial(5));
```
You can execute this program by running `val factorial.val`, which will write to
standard output `120`.
Lastly, you may want to evaluate a **val** expression and use it within another
program. The tool supports executing arbitrary expressions inline using the
`--expression` or `-e` option:
```bash
val -p 53 -e 'sin(2) * e ^ pi * cos(sum([1, 2, 3]))'
16.481455793912883588
```
**n.b.** The `--expression` option and `filename` argument are mutually
exclusive.
## Features
This section describes some of the language features **val** implements in
detail, and should serve as a guide to anyone wanting to write a **val**
program.
### Statements
**val** supports a few statement constructs such as `if`, `while`, `loop`, `fn`,
`return`, etc. Check out the [grammar](https://github.com/terror/val/blob/master/GRAMMAR.txt)
for all of the various statement types.
Here's an example showcasing most of them in action:
```rust
fn fib(n) {
if (n <= 1) {
return n
}
return fib(n - 1) + fib(n - 2)
}
i = 0
while (i < 10) {
println("fib(" + i + ") = " + fib(i))
i = i + 1
}
```
### Expressions
**val** supports a variety of expressions that can be combined to form more
complex operations:
| **Arithmetic** | Addition | `a + b` | `1 + 2` |
| | Subtraction | `a - b` | `5 - 3` |
| | Multiplication | `a * b` | `4 * 2` |
| | Division | `a / b` | `10 / 2` |
| | Modulo | `a % b` | `7 % 3` |
| | Exponentiation | `a ^ b` | `2 ^ 3` |
| | Negation | `-a` | `-5` |
| **Logical** | And | `a && b` | `true && false` |
| | Or | <code>a || b</code> | <code>true || false</code> |
| | Not | `!a` | `!true` |
| **Comparison** | Equal | `a == b` | `x == 10` |
| | Not Equal | `a != b` | `y != 20` |
| | Less Than | `a < b` | `a < b` |
| | Less Than or Equal | `a <= b` | `i <= 5` |
| | Greater Than | `a > b` | `count > 0` |
| | Greater Than or Equal | `a >= b` | `value >= 100` |
| **Other** | Function Call | `function(args)` | `sin(x)` |
| | List Indexing | `list[index]` | `numbers[0]` |
| | List Creation | `[item1, item2, ...]` | `[1, 2, 3]` |
| | List Concatenation | `list1 + list2` | `[1, 2] + [3, 4]` |
| | String Concatenation | `string1 + string2` | `"Hello, " + name` |
| | Variable Reference | `identifier` | `x` |
### Values
**val** has several primitive value types:
#### Number
Numeric values are represented as arbitrary precision floating point numbers (using
[astro_float](https://docs.rs/astro-float/latest/astro_float/index.html) under
the hood):
```rust
> pi
3.141592653589793115997963468544185161590576171875
> e
2.718281828459045090795598298427648842334747314453125
> sin(2) * e ^ pi * cos(sum([1, 2, 3]))
16.4814557939128835908118223753548409318930600432600320575175542910885566534716862696709583557263450637540094805515971245058657340687939442764118452427864231041058959960049996970569867866035825048029794926250103816423751837050040821914044725396611746570949840536443560831710407959633707222226883928822125018007
>
```
You can specify the rounding mode, and what sort of precision you'd like to see
in the output by using the `--rounding-mode` and `--precision` options
respectively.
#### Boolean
Boolean values represent truth values:
```rust
a = true
b = false
c = a && b
d = a || b
e = !a
```
#### String
Text values enclosed in single or double quotes:
```rust
greeting = "Hello"
name = 'World'
message = greeting + ", " + name + "!"
```
#### List
Collections of values of any type:
```rust
numbers = [1, 2, 3, 4, 5]
mixed = [1, "two", true, [3, 4]]
empty = []
first = numbers[0]
numbers[0] = 10
combined = numbers + [6, 7]
```
#### Function
A function is a value, and can be used in assignments, passed around to other
functions, etc.
Check out the [higher order functions example](https://github.com/terror/val/blob/master/examples/hoc.val)
for how this works.
```rust
fn reduce(l, f, initial) {
i = 0
result = initial
while (i < len(l)) {
result = f(result, l[i])
i = i + 1
}
return result
}
fn sum(a, b) {
return a + b
}
l = [1, 2, 3, 4, 5]
println(reduce(l, sum, 0))
```
#### Null
Represents the absence of a value.
```rust
fn search(l, x) {
i = 0
while (i < len(l)) {
if (l[i] == x) {
return i
}
i = i + 1
}
}
l = [1, 2, 3, 4, 5]
index = search(l, 6)
if (index == null) {
println("Value not found")
} else {
println("Value found at index " + index)
}
```
### Built-ins
**val** offers a many built-in functions and constants:
| **Constants** | `pi` | Mathematical constant π (≈3.14159) | `area = pi * r^2` |
| | `e` | Mathematical constant e (≈2.71828) | `growth = e^rate` |
| | `phi` | Golden ratio φ (≈1.61803) | `ratio = phi * width` |
| | `tau` | Tau constant τ (≈6.28318, 2π) | `circum = tau * r` |
| **Trigonometric** | `sin(x)` | Sine of x (radians) | `sin(pi/2)` |
| | `cos(x)` | Cosine of x (radians) | `cos(0)` |
| | `tan(x)` | Tangent of x (radians) | `tan(pi/4)` |
| | `csc(x)` | Cosecant of x (radians) | `csc(pi/6)` |
| | `sec(x)` | Secant of x (radians) | `sec(0)` |
| | `cot(x)` | Cotangent of x (radians) | `cot(pi/4)` |
| **Inverse Trig** | `asin(x)` | Arc sine (-1≤x≤1) | `asin(0.5)` |
| | `acos(x)` | Arc cosine (-1≤x≤1) | `acos(0.5)` |
| | `arc(x)` | Arc tangent | `arc(1)` |
| | `acsc(x)` | Arc cosecant (abs(x)≥1) | `acsc(2)` |
| | `asec(x)` | Arc secant (abs(x)≥1) | `asec(2)` |
| | `acot(x)` | Arc cotangent | `acot(1)` |
| **Hyperbolic** | `sinh(x)` | Hyperbolic sine | `sinh(1)` |
| | `cosh(x)` | Hyperbolic cosine | `cosh(1)` |
| | `tanh(x)` | Hyperbolic tangent | `tanh(1)` |
| **Logarithmic** | `ln(x)` | Natural logarithm | `ln(e)` |
| | `log2(x)` | Base-2 logarithm | `log2(8)` |
| | `log10(x)` | Base-10 logarithm | `log10(100)` |
| | `e(x)` | e raised to power x | `e(2)` |
| **Numeric** | `sqrt(x)` | Square root (x≥0) | `sqrt(16)` |
| | `ceil(x)` | Round up to integer | `ceil(4.3)` |
| | `floor(x)` | Round down to integer | `floor(4.7)` |
| | `abs(x)` | Absolute value | `abs(-5)` |
| **Collections** | `len(x)` | Length of list or string | `len("hello")` |
| | `sum(list)` | Sum list elements | `sum([1,2,3])` |
| **Conversion** | `int(x)` | Convert to integer | `int("42")` |
| | `float(x)` | Convert to float | `float("3.14")` |
| | `bool(x)` | Convert to boolean | `bool(1)` |
| | `list(x)` | Convert to list | `list("abc")` |
| **I/O** | `print(...)` | Print without newline | `print("Hello")` |
| | `println(...)` | Print with newline | `println("World")` |
| | `input([prompt])` | Read line from stdin | `name = input("Name: ")` |
| **String** | `split(str, delim)` | Split string | `split("a,b,c", ",")` |
| | `join(list, delim)` | Join list elements | `join(["a","b"], "-")` |
| **Program** | `exit([code])` | Exit program | `exit(1)` |
| | `quit([code])` | Alias for exit | `quit(0)` |
## Prior Art
[bc(1)](https://linux.die.net/man/1/bc) - An arbitrary precision calculator
language