AML ReferenceProgrammable Constructs
AML If-else
Control-flow expression to conditionally evaluate and return values in AML.
Introduction
AML if-else is a control-flow expression. It evaluates a Boolean condition and returns the value of the executed block. The value of the if-else expression is the value of the last expression inside the executed block.
- When used as a standalone statement,
elseis optional. - When used within another expression (for example, assignment or string interpolation), the expression must evaluate to a value on all paths; include an
else(orelse if … else) branch.
Syntax
// single branch
if (condition) {
expression
}
// with else clauses
if (condition1) {
expression1
} else if (condition2) {
expression2
} else {
expression3
}- Parentheses are required around conditions.
- Braces are required around blocks.
- Conditions must be Boolean expressions.
Examples
const a = 1
if (a > 0) {
'positive'
} else if (a == 0) {
'zero'
} else {
'negative'
}
// returns 'positive'const a = 1
const b = if (a > 0) {
'positive'
} else if (a == 0) {
'zero'
} else {
'negative'
}
b // 'positive'String interpolation example:
Func greet(name: 'John' | 'Alice') {
"Hello, ${if (name == 'John') { 'sir' } else { 'madam' }}!"
}Analytics-focused examples
Conditional metric selection in a KPI block:
// Renders a KPI block for either revenue (sum) or orders (count)
Func kpi_block(metric: 'revenue' | 'orders') {
const measure_ref = if (metric == 'revenue') {
r(fact_orders.revenue)
} else {
r(fact_orders.id)
}
VizBlock {
label: "KPI - ${metric}" // dynamic label derived from selected metric
viz: SingleValue {
dataset: 'ecommerce'
series {
field {
ref: measure_ref
aggregation: if (metric == 'revenue') { 'sum' } else { 'count' }
}
}
}
}
}Conditional grouping dimension for a distribution chart:
// Switches the grouping between product category and country
Func distribution_block(by: 'category' | 'country') {
const group_dim = if (by == 'category') {
r(products.category)
} else {
r(countries.name)
}
VizBlock {
label: "Distribution by ${by}" // dynamic label derived from grouping parameter
viz: PieChart {
dataset: 'ecommerce'
legend: group_dim
series {
field {
ref: r(orders.id)
aggregation: 'count'
}
}
}
}
}Type of an if-else expression
The type is the union of all possible branch result types.
Func gen_dashboard_block(block_type: DashboardBlock) {
if (block_type == VizBlock) {
VizBlock { ... }
} else if (block_type == FilterBlock) {
FilterBlock { ... }
} else {
TextBlock { ... }
}
}
// gen_dashboard_block return type: VizBlock | FilterBlock | TextBlockGuidelines:
- Branches used in an expression context should return compatible types or a meaningful union.
- If a branch yields no value, it cannot be used where a value is required.
AML comparison operators
==: true if operands are equal!=: true if operands are not equal>: true if left is greater than right>=: true if left is greater than or equal to right<: true if left is less than right<=: true if left is less than or equal to right
Examples:
3 == 3 // true
4 != 5 // true
5 > 2 // true
2 >= 2 // true
1 < 3 // true
2 <= 1 // falseAML logical operators
&&: true if both operands are true||: true if at least one operand is true!: logical negation
Examples:
true && false // false
true && true // true
true || false // true
false || false // false
!true // false
!false // true