Patternia v0.9.1 Release Note¶

Release Date: March 18, 2026 Version: 0.9.1

Overview¶

Patternia v0.9.1 is an API refinement and packaging stabilization release.

Compared with v0.9.0, this version finishes the roadmap transition from function-style static patterns to variable-template entry points, promotes the new structural and literal forms across the public docs, and tightens the vcpkg packaging flow for clean installs.

New Features¶

`val<V>` Replaces `lit<V>()`¶

Compile-time literal matching now uses val<V>:

match(x) | PTN_ON(
  val<1> >> 1,
  val<2> >> 2,
  _ >> 0
);

This aligns static literal patterns with the existing variable-template style used by is<T> and alt<I>.

Runtime literal patterns are unchanged:

match(x) | on(
  lit(1) >> "one",
  _ >> "other"
);

C++20 Floating-Point Static Literals¶

When you compile Patternia in C++20 or later mode, val<V> now accepts floating-point non-type template parameters:

match(x) | on(
  val<3.25> >> "three-point-two-five",
  _ >> "other"
);

In C++17 builds, floating-point static literals remain unavailable by design. Use lit(3.25) there.

`has<...>` Is Now the Canonical Structural Entry¶

Structural matching continues the same DSL direction as val<V>:

match(p) | on(
  $(has<&Point::x, &Point::y>) >> [](int x, int y) {
    return x + y;
  },
  _ >> 0
);

The old has<...>() factory-style spelling is no longer part of the public surface.

vcpkg Packaging Follow-Up¶

This release keeps the vcpkg port aligned with the upstream install layout and documents vcpkg as the primary installation path. It also includes the cleanup needed for a clean package install after the initial v0.9.0 port landing.

Migration Notes¶

`lit<V>()` -> `val<V>`¶

// Before
match(x) | on(
  lit<1>() >> 1,
  lit<2>() >> 2,
  _ >> 0
);

// After
match(x) | on(
  val<1> >> 1,
  val<2> >> 2,
  _ >> 0
);

`has<...>()` -> `has<...>`¶

// Before
$(has<&Point::x, &Point::y>()) >> [](int x, int y) {
  return x + y;
}

// After
$(has<&Point::x, &Point::y>) >> [](int x, int y) {
  return x + y;
}

C++17 vs C++20 Static Floating-Point Matching¶

// C++17
match(x) | on(
  lit(3.25) >> "three-point-two-five",
  _ >> "other"
);

// C++20+
match(x) | on(
  val<3.25> >> "three-point-two-five",
  _ >> "other"
);

Internal¶

include/ptn/pattern/lit.hpp: replaced the compile-time literal factory function with the val<V> variable template.
include/ptn/patternia.hpp: re-exported val through the umbrella header.
tests/compile_fail/: added regression coverage for removed lit<V>() and has<...>() forms, plus pre-C++20 floating-point static literals.
packaging/vcpkg/: version metadata updated for the 0.9.1 release cycle.