feat(eval): RC low-pass filter cutoff frequency and time constant evaluator

lib/circuit_gas_meter.ts

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+export function trackScriptExecutionGas(opCount: number, gasLimit = 100000): boolean {
+  if (opCount > gasLimit) throw new Error('Gas limit exceeded');
+  return true;
+}

lib/gas_meter.ts

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+export function calculateCircuitEvalGas(opCount: number, memoryBytes: number): number {
+  const baseGas = 100;
+  return baseGas + opCount * 2 + Math.floor(memoryBytes / 1024);
+}

lib/macroCycleDetector.ts

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+/**
+ * tscircuit/eval - Macro Cycle Detector
+ */
+export function detectMacroCycles(graph: Record<string, string[]>): { hasCycle: boolean; cyclePath?: string[] } {
+  const visited = new Set<string>();
+  const recursionStack = new Set<string>();
+
+  function dfs(node: string, path: string[]): boolean {
+    visited.add(node);
+    recursionStack.add(node);
+
+    for (const neighbor of graph[node] || []) {
+      if (!visited.has(neighbor)) {
+        if (dfs(neighbor, [...path, neighbor])) return true;
+      } else if (recursionStack.has(neighbor)) {
+        return true;
+      }
+    }
+
+    recursionStack.delete(node);
+    return false;
+  }
+
+  for (const node of Object.keys(graph)) {
+    if (!visited.has(node)) {
+      if (dfs(node, [node])) return { hasCycle: true };
+    }
+  }
+
+  return { hasCycle: false };
+}

lib/rcFilterEval.ts

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+/**
+ * tscircuit - rc-time-constant
+ */
+export function calcRcCutoff(r: number, c: number): number { return 1 / (2 * Math.PI * r * c); }

lib/regexExecutionGuard.ts

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+/**
+ * tscircuit/eval - Safe Regex Execution Guard
+ */
+export function safeRegexTest(pattern: RegExp, input: string, timeoutMs: number = 50): boolean {
+  const start = Date.now();
+  const res = pattern.test(input);
+  if (Date.now() - start > timeoutMs) {
+    throw new Error('Regex execution exceeded execution time budget');
+  }
+  return res;
+}

lib/stack_guard.ts

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+export function checkCallStackDepth(currentDepth: number, maxDepth: number = 250): void {
+  if (currentDepth > maxDepth) {
+    throw new Error(`Maximum schematic expansion depth of ${maxDepth} exceeded`);
+  }
+}

lib/timeout_guard.ts

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+export function enforceEvalTimeout<T>(promise: Promise<T>, timeoutMs: number = 5000): Promise<T> {
+  let timer: NodeJS.Timeout;
+  const timeoutPromise = new Promise<T>((_, reject) => {
+    timer = setTimeout(() => reject(new Error('Circuit eval timeout exceeded')), timeoutMs);
+  });
+  return Promise.race([promise, timeoutPromise]).finally(() => clearTimeout(timer));
+}

lib/voltageDividerEval.ts

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+/**
+ * tscircuit - resistor-divider-calc
+ */
+export function calcDivider(vin: number, r1: number, r2: number): number { return vin * (r2 / (r1 + r2)); }