DSQLEX - A SQL-like DSL for evaluating calculations in Elixir.
Usage
# Define a calculation expression (SELECT is optional)
expression = "CASE WHEN category = 'A' THEN x ELSE (y / z) END"
# Create a context with your data
context = %{
"x" => Decimal.new("100.00"),
"y" => Decimal.new("500.00"),
"category" => "B",
"z" => Decimal.new("5.00")
}
# Evaluate!
{:ok, result} = Dsqlex.eval(expression, context)
# => {:ok, Decimal.new("100")}Supported Features
- Arithmetic:
+,-,*,/ - Comparison:
=,!=,<,>,<=,>= - Logical:
AND,OR(same-operator chaining allowed) - Control flow:
CASE WHEN ... THEN ... ELSE ... END - Functions:
ROUND(),COALESCE(),UPPER(),LOWER(),ABS(),CONCAT() - Literals: Numbers, strings, booleans, NULL
Parentheses Rule
To avoid ambiguity, expressions that mix operator groups require parentheses:
# Valid
"1 + 2"
"1 + 2 + 3"
"(1 + 2) * 3"
"a = 1 AND b = 2 AND c = 3"
# Invalid (ambiguous)
"1 + 2 * 3"
"a = 1 AND b = 2 OR c = 3"Summary
Functions
Evaluates an expression against a context.
Parses an expression and returns the AST without evaluating.
Tokenizes an expression without parsing.
Functions
Evaluates an expression against a context.
The SELECT keyword is optional.
Parameters
expression- A string containing the expressioncontext- A map of field names (strings) to values
Returns
{:ok, result}- The computed result{:error, reason}- If lexing, parsing, or evaluation fails
Examples
iex> Dsqlex.eval("1 + 2", %{})
{:ok, Decimal.new("3")}
iex> Dsqlex.eval("x * 2", %{"x" => Decimal.new("50")})
{:ok, Decimal.new("100")}Parses an expression and returns the AST without evaluating.
Useful for validating expressions before storing them.
The SELECT keyword is optional.
Examples
iex> Dsqlex.parse("x / y")
{:ok, {:select, {:binary_op, :divide, {:identifier, "x"}, {:identifier, "y"}}}}Tokenizes an expression without parsing.
Useful for debugging or inspecting the lexer output.