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perf(engine): reuse Decimal(0) and Decimal(1) instances (#106)

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Added exported constants `DEC_ZERO` and `DEC_ONE` in `src/engine/types.ts`
and replaced all instances of `new Decimal(0)` and `new Decimal(1)`
across `src/engine/evaluator.ts` with these constants.
This reduces unnecessary memory allocations and garbage collection
overhead in the evaluator engine, especially during hot loops like
goal seek (root finding).

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
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Horizontal42 2026-08-19 16:36:10 +03:00 • committed by GitHub
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commit 12ae91da2e
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2 changed files with 16 additions and 14 deletions
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28
src/engine/evaluator.ts
View file

@ -1,6 +1,6 @@
// Walks the AST with the document context (variables, line results for
// sum/avg/prev) and produces unit-aware values.
import { Decimal, EvalError, PI, Quantity, Unit, Value, XRefError, qty, pct } from "./types";
import { Decimal, DEC_ZERO, DEC_ONE, EvalError, PI, Quantity, Unit, Value, XRefError, qty, pct } from "./types";
import { Node, ConvTarget } from "./parser";
import { Registry } from "./registry";
import { resolveZone, startOfToday, addToDate, isCalendarUnit } from "./datetime";
@ -148,10 +148,10 @@ function evalPercentArith(op: "plus" | "minus" | "mul" | "div" | "mod" | "pow",
const q = (l.kind === "quantity" ? l : r) as Quantity;
const p = (l.kind === "percent" ? l : r as { kind: "percent"; value: Decimal }).value;
switch (op) {
case "plus": return qty(q.value.mul(new Decimal(1).add(p.div(100))), q.unit);
case "plus": return qty(q.value.mul(DEC_ONE.add(p.div(100))), q.unit);
case "minus":
if (l.kind === "percent") throw new EvalError("percent minus number");
return qty(q.value.mul(new Decimal(1).sub(p.div(100))), q.unit);
return qty(q.value.mul(DEC_ONE.sub(p.div(100))), q.unit);
case "mul": return qty(q.value.mul(p).div(100), q.unit);
case "div":
if (l.kind === "percent") throw new EvalError("percent div number");
@ -257,8 +257,8 @@ function evalPctOp(op: string, l: Value, r: Value): Value {
const p = asPercentValue(l);
const factor =
op === "of" ? p.div(100)
: op === "off" ? new Decimal(1).sub(p.div(100))
: new Decimal(1).add(p.div(100));
: op === "off" ? DEC_ONE.sub(p.div(100))
: DEC_ONE.add(p.div(100));
// a percent of a percent stays a percent: 50% of 50% = 25%
if (r.kind === "percent") return pct(r.value.mul(factor));
return qty(rv.mul(factor), unit);
@ -268,7 +268,7 @@ function evalPctOp(op: string, l: Value, r: Value): Value {
if (rv.isZero()) throw new EvalError("division by zero");
switch (op) {
case "as_pct_of": return pct(lv.div(rv).mul(100));
case "as_pct_off": return pct(new Decimal(1).sub(lv.div(rv)).mul(100));
case "as_pct_off": return pct(DEC_ONE.sub(lv.div(rv)).mul(100));
case "as_pct_on": return pct(lv.div(rv).sub(1).mul(100));
}
}
@ -277,11 +277,11 @@ function evalPctOp(op: string, l: Value, r: Value): Value {
switch (op) {
case "of_what_is": return qty(rv.div(p.div(100)), unit);
case "off_what_is": {
const d = new Decimal(1).sub(p.div(100));
const d = DEC_ONE.sub(p.div(100));
if (d.isZero()) throw new EvalError("division by zero");
return qty(rv.div(d), unit);
}
case "on_what_is": return qty(rv.div(new Decimal(1).add(p.div(100))), unit);
case "on_what_is": return qty(rv.div(DEC_ONE.add(p.div(100))), unit);
}
throw new EvalError(`bad percent op ${op}`);
}
@ -392,7 +392,7 @@ function evalGoalSeek(lhsNode: Node, rhsNode: Node, ctx: EvalCtx): Value {
const innerCtx: EvalCtx = { ...ctx, vars };
const lv = evaluate(lhsNode, innerCtx);
const rv = evaluate(rhsNode, innerCtx);
const toD = (v: Value) => v.kind === "quantity" ? toBase(v) : new Decimal(0);
const toD = (v: Value) => v.kind === "quantity" ? toBase(v) : DEC_ZERO;
return toD(lv).minus(toD(rv));
};
@ -400,8 +400,8 @@ function evalGoalSeek(lhsNode: Node, rhsNode: Node, ctx: EvalCtx): Value {
try { return evalF(x); } catch { return null; }
};
const f0 = safeEval(new Decimal(0));
const f1 = safeEval(new Decimal(1));
const f0 = safeEval(DEC_ZERO);
const f1 = safeEval(DEC_ONE);
if (f0 !== null && f1 !== null) {
const slope = f1.minus(f0);
@ -483,7 +483,7 @@ const AGG_FUNCS: Record<string, (block: Quantity[]) => Value> = {
},
min: (block) => filterSameDimension(block).reduce((best, q) => toBase(q).lt(toBase(best)) ? q : best),
max: (block) => filterSameDimension(block).reduce((best, q) => toBase(q).gt(toBase(best)) ? q : best),
product: (block) => qty(block.reduce((acc, q) => acc.mul(q.value), new Decimal(1))),
product: (block) => qty(block.reduce((acc, q) => acc.mul(q.value), DEC_ONE)),
sum: (block) => reduceCompatible(block).acc,
avg: (block) => {
const { acc, counted } = reduceCompatible(block);
@ -554,7 +554,7 @@ function evalCall(name: string, args: Value[], ctx: EvalCtx): Value {
case "sin": return qty(Decimal.sin(angleArg()));
case "cos": return qty(Decimal.cos(angleArg()));
case "tan": return qty(Decimal.tan(angleArg()));
case "cot": return qty(new Decimal(1).div(Decimal.tan(angleArg())));
case "cot": return qty(DEC_ONE.div(Decimal.tan(angleArg())));
case "asin": case "arcsin": return qty(Decimal.asin(n()));
case "acos": case "arccos": return qty(Decimal.acos(n()));
case "atan": case "arctan": return qty(Decimal.atan(n()));
@ -613,7 +613,7 @@ function mulberry32(seed: number): number {
function factorial(n: Decimal): Decimal {
if (!n.isInteger() || n.isNegative() || n.gt(300)) throw new EvalError("bad factorial");
let acc = new Decimal(1);
let acc = DEC_ONE;
for (let i = 2; i <= n.toNumber(); i++) acc = acc.mul(i);
return acc;
}

2
src/engine/types.ts
View file

@ -6,6 +6,8 @@ export { Decimal };
/** Shared here (not in evaluator.ts) so unitdata.ts can use it too without a cycle. */
export const PI = new Decimal("3.14159265358979323846264338327950288419716939937510");
export const DEC_ZERO = new Decimal(0);
export const DEC_ONE = new Decimal(1);
export type Dimension =
| "scalar"