Dala Formula Language

The Dala Formula Language is a light weight language, that is heavily inspired by Excel and Google Sheets formulas, for example: SUM(1, 2, 3, 4, 5) will yield 15.

It is currently a work in progress.

The Rust API

You can use the dala::eval To evaluate a Dala from expression inside a Rust program. For example:

use dala::{eval, DalaValue};

let result = eval("CONCAT(\"Hello\", \" \", \"World\")");

let DalaValue::Str(value) = result[0].as_ref().unwrap() else { panic!("Not a string") };
assert_eq!(value, "Hello World");

The eval function

The eval function takes a string slice and returns a Vec<Result<DalaValue, DalaError>>, with the result of each expression that was evaluated.

The DalaValue enum represents the possible values that can be returned from a Dala expression: a Str, a Num or a Boolean.

The DalaError enum represents the possible errors that can occur during the evaluation:

• BuildError: returned when there is an processing the Dala Expression, before its evaluation.
• RuntimeError: returned when there is an error during the evaluation of the Dala Expression.
• ParseError: returned when there is an error parsing the Dala Expression.

The Repl

You can try out the language on our Repl, by using this command: cargo run -p repl.

Once it is running, just type in your Dala Expression and press enter to evaluate it, for example:

> CONCAT("Hello", " ", "World")
"Hello World"

The Language

Primitives

These primitive values are used as arguments and as return values from functions.

Primitive	Description	Syntax
Str	A string of characters enclosed by double quotes	"Hello World"
Num	A number	1, 2.5, 3.1415
Boolean	A boolean value	TRUE, FALSE

Functions

Each function can take primitive or other functions as arguments.

Function	Syntax	Example	Description
EQ	EQ(a, b) -> Boolean	EQ(1, 1) -> TRUE	Returns TRUE if the arguments are equal, otherwise returns FALSE
NEQ	EQ(a, b) -> Boolean	EQ(1, 1) -> FALSE	Returns TRUE if the arguments are different, otherwise returns FALSE
CONCAT	CONCAT(a, b, c, ...) -> Str	CONCAT("Hello", " ", "World") -> "Hello World"	Concatenates all the arguments together into a single string
DIVIDE	DIVIDE(a, b) -> Num	DIVIDE(10, 2) -> 5	Divides the first argument by the second argument
IF	IF(condition, if_true, if_false) -> Lit	IF(TRUE, "Hello", "World") -> "World"	If the condition is true, evaluates if_true, otherwise evaluates if_false
MULTIPLY	MULTIPLY(a, b) -> Num	MULTIPLY(5, 2) -> 10	Multiplies the arguments
SUBTRACT	SUBTRACT(a, b) -> Num	SUBTRACT(1, 2) -> -1	Subtracts the second argument from the first
SUM	SUM(a, b, c, ...) -> Num	SUM(1, 2, 3, 4, 5) -> 15	Sums all the arguments together
UPPER	UPPER(a) -> Str	UPPER("Hello World") -> "HELLO WORLD"	Converts the string to upper case