val

val (eval) is a simple arbitrary precision calculator language built on top of chumsky and ariadne.

Installation

val should run on any system, including Linux, MacOS, and the BSDs.

The easiest way to install it is by using cargo, the Rust package manager:

cargo install val

Pre-built binaries

Pre-built binaries for Linux, MacOS, and Windows can be found on the releases page.

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:

val 0.3.6
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
  -l, --load <LOAD>                    Load files before entering the REPL
  -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]
      --stack-size <STACK_SIZE>        Stack size in MB for evaluations [default: 128]
  -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 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 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:

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:

val -p 53 -e 'sin(2) * e ^ pi * cos(sum([1, 2, 3]))'
20.203684508229124193

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 for all of the various statement types.

Here's an example showcasing most of them in action:

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:

Category	Operation	Syntax	Example
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	a || b	true || false
	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 under the hood):

> 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:

a = true
b = false
c = a && b
d = a || b
e = !a

String

Text values enclosed in single or double quotes:

greeting = "Hello"
name = 'World'
message = greeting + ", " + name + "!"

List

Collections of values of any type:

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 for how this works.

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.

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:

Category	Function/Constant	Description	Example
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)
	gcd(a, b)	Greatest common divisor	gcd(12, 8)
	lcm(a, b)	Least common multiple	lcm(4, 6)
Collections	len(x)	Length of list or string	len("hello")
	sum(list)	Sum list elements	sum([1,2,3])
	append(list, val)	Add element to end of list	append([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) - An arbitrary precision calculator language