ts-07-mathjs-evaluate

# Compile and evaluate expressions (mathjs)

Implement **`solution.ts`** using **mathjs** (already installed — import what you need,
e.g. `import { compile } from "mathjs";`).

Export exactly one function:

```ts
export function evaluateAll(expr: string, scopes: Record<string, number>[]): number[];
```

Behavior:

- **Compile the expression once** with mathjs (`compile(expr)`), then evaluate the
  compiled expression against **each** scope in `scopes`, in order.
- Return an array of the numeric results (one per scope). Convert each result to a
  `number` so the return type is exactly `number[]`.
- An empty `scopes` array returns `[]`.

The expression may reference variables supplied by the scope and may use mathjs built-in
functions (e.g. `sqrt`, `max`, `sin`).

Examples:
```ts
evaluateAll("a^2 + b", [{ a: 3, b: 1 }, { a: 2, b: 5 }]);
// => [10, 9]

evaluateAll("sqrt(x) + max(y, 1)", [{ x: 9, y: 4 }]);
// => [7]   // sqrt(9)=3, max(4,1)=4

evaluateAll("a + b", []);
// => []
```

Keep it fully typed (must pass `tsc --noEmit` in strict mode). Do not use `any` in the
public API.

import { test } from "node:test";
import { strict as assert } from "node:assert";
import { evaluateAll } from "./solution.ts";

test("evaluates with multiple variables across scopes", () => {
  assert.deepEqual(evaluateAll("a^2 + b", [{ a: 3, b: 1 }, { a: 2, b: 5 }]), [10, 9]);
});

test("preserves scope order", () => {
  assert.deepEqual(evaluateAll("x * 10", [{ x: 1 }, { x: 2 }, { x: 3 }]), [10, 20, 30]);
});

test("uses built-in functions", () => {
  assert.deepEqual(evaluateAll("sqrt(x) + max(y, 1)", [{ x: 9, y: 4 }]), [7]);
});

test("empty scopes returns empty array", () => {
  assert.deepEqual(evaluateAll("a + b", []), []);
});

test("single scope", () => {
  assert.deepEqual(evaluateAll("2 * a + 1", [{ a: 20 }]), [41]);
});

test("result is a number array", () => {
  const out = evaluateAll("a / b", [{ a: 6, b: 2 }, { a: 9, b: 3 }]);
  assert.equal(typeof out[0], "number");
  assert.deepEqual(out, [3, 3]);
});

test("compiles once and reuses for differing variable values", () => {
  const out = evaluateAll("a + b + c", [
    { a: 1, b: 2, c: 3 },
    { a: 10, b: 20, c: 30 },
  ]);
  assert.deepEqual(out, [6, 60]);
});

You are an expert programmer. Solve the task exactly as specified. Output your solution as fenced code blocks using the required file name(s) and the exact function/type signatures requested. Prefer correctness; do not include prose outside code unless asked.

```ts
import { compile, CompiledExpression } from "mathjs";

export function evaluateAll(expr: string, scopes: Record<string, number>[]): number[] {
  const compiled: CompiledExpression = compile(expr);
  return scopes.map(scope => Number(compiled.evaluate(scope)));
}
```

The user wants a TypeScript function `evaluateAll` that:
1. Takes an expression string and an array of scopes (each scope is a Record<string, number>)
2. Compiles the expression once using mathjs's `compile`
3. Evaluates the compiled expression against each scope
4. Returns an array of numbers

Let me write this:

```ts
import { compile, CompiledExpression } from "mathjs";

export function evaluateAll(expr: string, scopes: Record<string, number>[]): number[] {
  const compiled = compile(expr);
  return scopes.map(scope => Number(compiled.evaluate(scope)));
}
```

This should work. Let me verify:
- `compile(expr)` returns a `CompiledExpression`
- `compiled.evaluate(scope)` evaluates with the given scope
- We convert each result to a `number` using `Number()`
- Empty scopes returns empty array (map on empty array is empty)
- No `any` used
- Fully typed

This looks correct and complete.