Operators Overview
datalogic-rs provides 59 built-in operators organized into logical categories. This section documents each operator with syntax, examples, and notes on behavior.
Operator Categories
| Category | Operators | Description |
|---|---|---|
| Variable Access | var, val, exists | Access and check data |
| Comparison | ==, ===, !=, !==, >, >=, <, <= | Compare values |
| Logical | !, !!, and, or | Boolean logic |
| Arithmetic | +, -, *, /, %, max, min, abs, ceil, floor | Math operations |
| Control Flow | if, ?:, ?? | Conditional branching |
| String | cat, substr, in, length, starts_with, ends_with, upper, lower, trim, split | String manipulation |
| Array | merge, filter, map, reduce, all, some, none, sort, slice | Array operations |
| DateTime | datetime, timestamp, parse_date, format_date, date_diff, now | Date and time |
| Missing Values | missing, missing_some | Check for missing data |
| Error Handling | try, throw | Exception handling |
Operator Syntax
All operators follow the JSONLogic format:
{ "operator": [arg1, arg2, ...] }
Some operators accept a single argument without an array:
{ "var": "name" }
// Equivalent to:
{ "var": ["name"] }
Lazy Evaluation
Several operators use lazy (short-circuit) evaluation:
and: Stops at first falsy valueor: Stops at first truthy valueif: Only evaluates the matching branch?:: Only evaluates the matching branch??: Only evaluates fallback if first value is null
This is important when operations have side effects or when you want to avoid errors:
{
"and": [
{ "var": "user" },
{ "var": "user.profile.name" }
]
}
If user is null, the second condition is never evaluated, avoiding an error.
Type Coercion
Operators handle types differently:
Loose vs Strict
==and!=perform type coercion===and!==require exact type match
{ "==": [1, "1"] } // true (loose)
{ "===": [1, "1"] } // false (strict)
Numeric Coercion
Arithmetic operators attempt to convert values to numbers:
{ "+": ["5", 3] } // 8 (string "5" becomes number 5)
Truthiness
Boolean operators use configurable truthiness rules. By default (JavaScript-style):
- Falsy:
false,0,"",null,[] - Truthy: Everything else
Custom Operators
You can add your own operators. See Custom Operators for details.
#![allow(unused)]
fn main() {
engine.add_operator("myop".to_string(), Box::new(MyOperator));
}Custom operators follow the same syntax:
{ "myop": [arg1, arg2] }