Introduction

Dew is a minimal expression language that compiles to multiple backends. Parse once, emit to WGSL (GPU shaders), Cranelift (native JIT), or Lua (scripting).

Part of the Rhizome ecosystem.

Architecture

dew-core               # Syntax only: AST, parsing
    |
    +-- dew-cond       # Conditional backend helpers
    |
    +-- dew-scalar     # Scalar domain: f32/f64 math functions
    |
    +-- dew-linalg     # Linalg domain: Vec2, Vec3, Mat2, Mat3
    |
    +-- dew-complex    # Complex numbers: [re, im]
    |
    +-- dew-quaternion # Quaternions: [x, y, z, w], Vec3

All domain crates have WGSL, Lua, and Cranelift backends (feature flags).

Core = syntax only, domains = semantics. Each domain crate has its own:

• Value types and type system
• Function registry
• Self-contained backends (behind feature flags)

Feature Flags

dew-core uses feature flags to manage complexity:

Feature	Description
(none)	Basic expressions: numbers, variables, arithmetic
cond	Conditionals: if/then/else, comparisons (<, >=, ==), boolean logic (and, or, not)
func	Function calls: name(args...) with extensible registry

Domain crates automatically enable func (they rely on function calls).

Quick Example

use rhizome_dew_core::Expr;
use rhizome_dew_scalar::{eval, scalar_registry};

// Parse an expression
let expr = Expr::parse("sin(x) + cos(y)").unwrap();

// Evaluate with variables
let mut vars = std::collections::HashMap::new();
vars.insert("x".to_string(), 0.5_f32);
vars.insert("y".to_string(), 1.0_f32);

let registry = scalar_registry();
let result = eval(expr.ast(), &vars, &registry).unwrap();

With Conditionals

When dew-core is compiled with the cond feature:

use rhizome_dew_core::Expr;
use rhizome_dew_scalar::{eval, scalar_registry};

// Conditional expression
let expr = Expr::parse("if x > 0 then sqrt(x) else 0").unwrap();

let mut vars = std::collections::HashMap::new();
vars.insert("x".to_string(), 9.0_f32);

let result = eval(expr.ast(), &vars, &scalar_registry()).unwrap();
// result = 3.0

Backends

Each domain crate includes three backends as optional features:

Backend	Feature	Use case
WGSL	wgsl	GPU shaders (WebGPU)
Lua	lua	Scripting, hot-reload
Cranelift	cranelift	Native JIT compilation

Enable in Cargo.toml:

[dependencies]
rhizome-dew-scalar = { version = "0.1", features = ["wgsl", "lua", "cranelift"] }

Crates

Crate	Description
rhizome-dew-core	Core AST and parsing (feature-gated conditionals and functions)
rhizome-dew-cond	Conditional backend helpers for domain crates
rhizome-dew-scalar	Scalar math: sin, cos, exp, lerp, etc.
rhizome-dew-linalg	Linear algebra: Vec2-4, Mat2-4, dot, cross, etc.
rhizome-dew-complex	Complex numbers: exp, log, polar, conjugate, etc.
rhizome-dew-quaternion	Quaternions: rotation, slerp, axis-angle, etc.