Expression evaluation

Laze supports inline expression evaluation using the $(...) syntax.

Expressions are evaluated after variable expansion (${...}), so variables are resolved first, then expressions are evaluated.

Expression evaluation is powered by the evalexpr crate.

Syntax

• $(expression) evaluates the expression and substitutes the result.
• Nesting is supported: inner expressions are evaluated first.
• $$(...) escapes the dollar sign and is not evaluated.

Examples

Arithmetic:

env:
  RESULT: "$(1 + 1)"
  # evaluates to "2"

Nested expressions:

env:
  RESULT: "$(1 + $(1 + 1))"
  # evaluates to "3"

Functions:

env:
  MAX_VAL: "$(max(1, 2, 3, 4))"
  # evaluates to "4"

String functions:

env:
  UPPER: '$(str::to_uppercase "foobar")'
  # evaluates to "FOOBAR"

Combined with variable expansion:

env:
  BASE: "10"
  OFFSET: "$(${BASE} + 5)"
  # evaluates to "15"

Supported operations

• Arithmetic: +, -, *, /, %, ^
• Comparison: ==, !=, <, <=, >, >=
• Boolean: &&, ||, !
• String concatenation: + (on strings)
• Conditional: if(condition, then, else)

Supported functions

Math: min, max, floor, ceil, round, abs, sqrt, exp, ln, log

String: str::to_uppercase, str::to_lowercase, str::trim, str::contains, str::starts_with, str::ends_with, str::len, str::from, str::substring, str::regex_matches, str::regex_replace