constExpr()

구문

function constExpr<T extends ShaderType>(
  name: string,
  type: T,
  value: Node,
): ConstExprDecl<T>

매개변수

name string

the emitted constant name, and the name every reference spells.

type T extends ShaderType

the constant’s shader type, emitted as its declared type.

value Node

a constant-foldable literal node holding the value.

반환값

ConstExprDecl<T>

the ConstDecl to put in module({ consts }), carrying .node.

설명

value is any constant-foldable literal node, a vec4(...), an arrayLit(...), a struct constructor. It emits const <name>: <type> = <value>; on both WGSL and GLSL ES 3.00, and the CPU oracle, the same module run in double precision on the CPU, evaluates the same expression, so all three agree on the value.

A scalar constant is the other form. constDecl takes a { wgsl, cpu } pair and writes them into a ConstDecl’s wgslValue and cpuValue: the shader gets the spelling you want in the source, often a truncated one such as 3.14159265, while the oracle evaluates the full double. constExpr has no such split, because a folded literal node carries one value for both.

The declaration carries .node, the typed reference to read it through, so the name is written once. Without it a reader is spelled constRef('SKY', vec4fT) — a string the type checker never compares against the declaration, and a second copy of the type, so a rename or a retype is silent at every call site until the GPU compiler sees it.

예제

import { constExpr, arrayLit, arrayT, vec4, vec4fT } from 'typeshade'

const SKY = constExpr('SKY', vec4fT, vec4(0.4, 0.6, 0.9, 1))
const PALETTE = constExpr('PALETTE', arrayT(vec4fT, 2), arrayLit(vec4fT, c0, c1))

const bg = fn('bg', {}, () => SKY.node) // no constRef('SKY', vec4fT)
const m = module({ consts: [SKY], funcs: [bg] })

관련 가이드

• 값과 변경

함께 보기

• constDecl
• module

소스

src/core/ir/builder.ts, 1383행, 커밋 c66579bf 기준