aimx::expressions

Module conditional

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Conditional expression parsing and evaluation.

This module provides the parsing and evaluation infrastructure for conditional expressions in the AIMX (Agentic Inference Markup Expressions) language. It specifically handles the ternary conditional operator (? :), which has right associativity and a specific precedence in the expression grammar.

§Operator Precedence

The conditional operator has higher precedence than closure expressions:

  1. Primary - Literals, references, parentheses
  2. Postfix - Method calls, indexing, function calls
  3. Unary - Prefix operators (!, +, -, casts)
  4. Multiplicative - Multiplication, division, modulo (*, /, %)
  5. Additive - Addition, subtraction (+, -)
  6. Relational - Comparison operators (<, <=, >, >=)
  7. Equality - Equality and inequality (=, !=)
  8. Logical - Logical AND and OR (&, |)
  9. Conditional - Ternary operator (?, :)
  10. Closure - Anonymous functions (=>)
  11. Procedure - Sequence expressions (;)

§Grammar

The conditional operator has the following grammar:

conditional := or_expression (S? '?' S? expression S? ':' S? conditional)?

Where S represents optional whitespace. The optional conditional part makes the operator right associative, meaning a ? b : c ? d : e is parsed as a ? b : (c ? d : e).

§Truthiness Evaluation

The condition expression is evaluated for truthiness using the following rules:

  • Boolean values: true evaluates to truthy, false to falsy
  • Arrays: Non-empty arrays are truthy, empty arrays are falsy
  • Other types: Converted to boolean using Rust’s standard truthiness rules
    • Numbers: Non-zero values are truthy, zero is falsy
    • Text: Non-empty strings are truthy, empty strings are falsy
    • Empty values: Always falsy

§AST Representation

The module uses AST flattening optimization where Conditional includes variants for all lower-precedence expression types. This allows efficient evaluation without deep recursion.

§Examples

§Basic Usage

5 > 3 ? "yes" : "no"              // → "yes"
true ? 1 : 0                      // → 1
x > 0 ? "positive" : "non-positive" // conditional assignment

§Complex Conditions

is_valid & (x > threshold) ? "pass" : "fail"
status == "completed" ? final_score : pending_score

§Right Associativity

a ? b : c ? d : e         // Parsed as: a ? b : (c ? d : e)
x > 0 ? 1 : y > 0 ? 2 : 3 // Parsed as: x > 0 ? 1 : (y > 0 ? 2 : 3)

§Runtime Behavior

  • Short-circuit evaluation: Only the selected branch (true or false) is evaluated
  • Error handling: Errors in the condition propagate immediately, errors in unselected branches are not evaluated
  • Type safety: The true and false expressions can have different types
  • logical - Higher precedence logical operations (&, |)
  • expression - Top-level expression parsing
  • evaluate - Core evaluation traits
  • primary - Lower precedence expressions

Enums§

Conditional
A conditional expression node in the abstract syntax tree.

Functions§

parse_conditional
Parse a conditional expression.