AML If-else

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, else is 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 (or else 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 | TextBlock

Guidelines:

• 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   // false

AML 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