Operators

Teckel's expression language provides arithmetic, comparison, logical, and special operators. This page documents each category and defines the precedence rules that govern evaluation order.

Operator Precedence Table

Operators are listed from highest precedence (evaluated first) to lowest precedence (evaluated last).

Precedence	Operator	Associativity	Description
1	(), function calls	—	Grouping, function application
2	unary -	Right	Numeric negation
3	*, /, %	Left	Multiplication, division, modulo
4	+, -	Left	Addition, subtraction
5	=, !=, <>, <, >, <=, >=, IS, IN, BETWEEN, LIKE	—	Comparison and special operators
6	NOT	Right	Logical negation
7	AND	Left	Logical conjunction
8	OR	Left	Logical disjunction
9	as	—	Aliasing (lowest)

Parentheses override default precedence. When in doubt, use them for clarity.

Precedence example:

NOT a AND b OR c

This parses as ((NOT a) AND b) OR c because NOT binds tighter than AND, which binds tighter than OR.

Arithmetic Operators

Arithmetic operators work on numeric types (integer, long, float, double, decimal).

Operator	Description	Example	Result
+	Addition	price + tax	Sum of price and tax
-	Subtraction	total - discount	Difference
*	Multiplication	price * quantity	Product
/	Division	total / count	Quotient
%	Modulo	id % 10	Remainder after division
unary -	Negation	-balance	Negated value

columns:
  - "price * quantity as line_total"
  - "(price * quantity) - discount as net_total"
  - "total / count as average"
  - "id % 100 as bucket"
  - "-balance as inverted_balance"

Any arithmetic operation involving NULL produces NULL:

x + NULL   -->  NULL
NULL * 5   -->  NULL

Comparison Operators

Comparison operators return a boolean result (or NULL when either operand is NULL).

Operator	Description	Example
=	Equal to	status = 'active'
!=	Not equal to	status != 'cancelled'
<>	Not equal to (alternative)	status <> 'cancelled'
<	Less than	age < 18
>	Greater than	amount > 1000
<=	Less than or equal to	score <= 100
>=	Greater than or equal to	balance >= 0

Canonical Equality

The canonical equality operator is = (single equals), consistent with ANSI SQL. The double-equals form == is accepted as an alias and is treated identically, but = is the preferred form.

# Preferred
condition: "status = 'active'"

# Also accepted, but not canonical
condition: "status == 'active'"

NULL Comparison Behavior

Comparing anything with NULL using =, !=, or any other comparison operator produces NULL, not true or false:

NULL = NULL     -->  NULL  (not true)
NULL != NULL    -->  NULL  (not true)
42 = NULL       -->  NULL

To test for NULL, use IS NULL or IS NOT NULL (see Special Operators below).

Logical Operators

Logical operators combine boolean expressions. Teckel follows SQL three-valued logic where the third value is NULL.

Operator	Description	Example
AND	Logical conjunction	age >= 18 AND status = 'active'
OR	Logical disjunction	role = 'admin' OR role = 'owner'
NOT	Logical negation	NOT is_deleted

Three-Valued Logic Truth Tables

AND:

Left	Right	Result
true	true	true
true	false	false
true	NULL	NULL
false	true	false
false	false	false
false	NULL	false
NULL	true	NULL
NULL	false	false
NULL	NULL	NULL

OR:

Left	Right	Result
true	true	true
true	false	true
true	NULL	true
false	true	true
false	false	false
false	NULL	NULL
NULL	true	true
NULL	false	NULL
NULL	NULL	NULL

NOT:

Input	Result
true	false
false	true
NULL	NULL

# Combine conditions
condition: "age >= 18 AND country = 'ES' AND NOT is_blacklisted"

# Either condition
condition: "role = 'admin' OR role = 'superadmin'"

# Grouping with parentheses
condition: "(status = 'active' OR status = 'pending') AND amount > 0"

Special Operators

IS NULL / IS NOT NULL

The only operators guaranteed to return true or false (never NULL) when testing for null values.

condition: "email IS NOT NULL"
condition: "deleted_at IS NULL"

Expression	Value is NULL	Value is not NULL
x IS NULL	true	false
x IS NOT NULL	false	true

IN

Tests whether a value matches any element in a list.

condition: "status IN ('active', 'pending', 'review')"
condition: "country_code IN ('ES', 'FR', 'DE', 'IT')"

The negated form excludes matches:

condition: "status NOT IN ('deleted', 'archived')"

BETWEEN

Tests whether a value falls within a closed range (inclusive of both endpoints).

condition: "age BETWEEN 18 AND 65"
condition: "order_date BETWEEN '2025-01-01' AND '2025-12-31'"

BETWEEN is equivalent to age >= 18 AND age <= 65. The negated form:

condition: "salary NOT BETWEEN 0 AND 999"

LIKE

Pattern matching for strings. Supports two wildcards:

Wildcard	Meaning
%	Matches zero or more characters
_	Matches exactly one character

condition: "name LIKE 'John%'"          # starts with "John"
condition: "email LIKE '%@example.com'"  # ends with "@example.com"
condition: "code LIKE 'A_B'"            # "A", any single char, "B"
condition: "name NOT LIKE '%test%'"      # does not contain "test"

Combined Examples

Operators can be freely combined, respecting the precedence table:

# Arithmetic inside comparison inside logical
condition: "price * quantity > 100 AND status = 'confirmed'"

# Multiple special operators
condition: "age BETWEEN 18 AND 65 AND country IN ('ES', 'FR') AND email IS NOT NULL"

# Parentheses to override default precedence
condition: "(priority = 'high' OR priority = 'critical') AND assigned_to IS NOT NULL"

# Expression with alias
columns:
  - "price * (1 - discount / 100.0) as discounted_price"