Skuld.Syntax (skuld v0.32.1)

Syntax module providing the computation do-notation macro.

Usage

use Skuld.Syntax

# Now you have access to:
# - comp (inline computation block)
# - defcomp, defcompp (function definitions)

Example

use Skuld.Syntax
alias Skuld.Effects.State

comp do
  x <- State.get()
  y = x + 1
  _ <- State.put(y)
  y
end

Defining Functions

defcomp increment() do
  x <- State.get()
  _ <- State.put(x + 1)
  x + 1
end

defcompp private_helper() do
  ctx <- Reader.ask()
  ctx.value
end

Query Syntax

For query, defquery, and defqueryp macros, use use Skuld.Query (provided by the skuld_query package).

Syntax Reference

• x <- effect() - bind the result of an effectful computation
• x = expr - pure variable binding (unchanged)
• Last expression is auto-lifted if not already a computation

Auto-Lifting

Non-computation values are automatically wrapped in Comp.pure/1. This means:

• Final expressions don't need wrapping: x + 1 works as final line
• if without else works: _ <- if cond, do: effect() (nil auto-lifted)
• Any plain value in a bind position is treated as a pure computation

See Also

• Skuld.Comp.CompBlock - macro implementation details
• Skuld.Comp - core computation primitives
• Skuld.Query - query do-notation macros (in skuld_query package)