Expression Syntax

Ordo uses a powerful expression language for defining conditions in rules.

Basic Syntax

Comparisons

age >= 18
status == "active"
score != 0
amount < 1000
count <= 10
level > 5

Logical Operators

# AND
age >= 18 && status == "active"

# OR
tier == "gold" || tier == "platinum"

# NOT
!is_blocked

# Combined
(age >= 18 && income > 30000) || has_cosigner == true

Arithmetic

price * quantity
total - discount
(base + bonus) * multiplier
amount / 100
count % 2

Field Access

Object Properties

user.name
order.items.count
profile.settings.notifications

Array Indexing

items[0]
items[0].price
users[1].name

Nested Access

data.users[0].profile.email
order.items[2].product.category

Built-in Functions

String Functions

Function	Description	Example
len(s)	String length	len(name) > 0
upper(s)	Uppercase	upper(code) == "VIP"
lower(s)	Lowercase	lower(email)
trim(s)	Remove whitespace	trim(input)
contains(s, sub)	Check substring	contains(email, "@")
starts_with(s, prefix)	Check prefix	starts_with(code, "PRE")
ends_with(s, suffix)	Check suffix	ends_with(file, ".pdf")

Array Functions

Function	Description	Example
len(arr)	Array length	len(items) > 0
sum(arr)	Sum of numbers	sum(prices) >= 100
avg(arr)	Average	avg(scores) > 70
min(arr)	Minimum value	min(bids)
max(arr)	Maximum value	max(scores) == 100

Numeric Functions

Function	Description	Example
abs(n)	Absolute value	abs(balance) < 100
round(n)	Round to nearest	round(price)
floor(n)	Round down	floor(score)
ceil(n)	Round up	ceil(amount)

Utility Functions

Function	Description	Example
exists(field)	Check if field exists	exists(discount)
coalesce(a, b, ...)	First non-null value	coalesce(nickname, name, "Guest")

Conditional Expressions

# If-then-else
if exists(discount) then price * (1 - discount) else price

# Nested conditionals
if tier == "gold" then 0.20
else if tier == "silver" then 0.10
else 0.05

Type Coercion

Ordo automatically handles type conversions:

# String to number comparison
"100" > 50  # true (string converted to number)

# Boolean expressions
1 == true   # true
0 == false  # true

Examples

Complex Discount Calculation

# VIP users get 20%, others get 5%
if user.vip == true then order.total * 0.80 else order.total * 0.95

Risk Score Evaluation

# Check multiple risk factors
credit_score >= 700 && debt_ratio < 0.4 && employment_years >= 2

Order Validation

# Validate order has items and meets minimum
len(order.items) > 0 && sum(order.items.*.price) >= 10

Null-safe Field Access

# Use coalesce for optional fields
coalesce(user.preferred_name, user.name, "Customer")

Array Aggregation

# Check if any item exceeds limit
max(order.items.*.quantity) <= 100

# Validate total
sum(cart.items.*.price) <= user.credit_limit

Operator Precedence

From highest to lowest:

1. () - Parentheses
2. ! - NOT
3. *, /, % - Multiplication, Division, Modulo
4. +, - - Addition, Subtraction
5. <, <=, >, >= - Comparisons
6. ==, != - Equality
7. && - AND
8. || - OR

Best Practices

1. Use parentheses for clarity: (a && b) || c is clearer than a && b || c
2. Check for existence: Use exists(field) before accessing optional fields
3. Use coalesce for defaults: coalesce(value, default) instead of complex conditionals
4. Keep expressions simple: Break complex logic into multiple steps
5. Test edge cases: Empty arrays, null values, missing fields