InterSystems·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Got a coding question at InterSystems that involved reading ObjectScript, which I had basically never touched before. It was a technical phone screen and the whole thing hinged on whether you could trace through some pretty niche language semantics under pressure.

Questions Asked (1)

Given a snippet of ObjectScript code where a global variable acts as a two-level ordered hashmap, trace through the execution step by step and predict the exact output. The key operation is a reverse-order iteration over the second-level subscript keys using $order with a direction argument of -1.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I had never written a line of ObjectScript in my life and they just dropped this on me.

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AI HintsAI Generated

Suggested Approach

First, identify the global's structure and the initial state of its subscripts. Then, simulate the $ORDER loop with direction -1, tracking the current subscript and the output at each iteration until the loop terminates. Finally, state the exact output sequence and explain why the loop ends when $ORDER returns an empty string.

Pro tip: Mention that $ORDER with -1 returns the previous subscript in collating order, and that the loop terminates when it returns an empty string. Also, note that the output order is reverse collating order, not reverse insertion order.

1. Understand the data structure

Recognize that the global is a two-level ordered hashmap: first-level subscripts map to second-level subscripts, which map to values. The second-level subscripts are automatically sorted in collating order.

2. Identify the iteration logic

The code uses $ORDER with a direction argument of -1 to iterate over the second-level subscripts in reverse order. Start from the highest subscript and move to the lowest.

3. Trace the loop step by step

Initialize the loop variable to the highest subscript (or use $ORDER to get it). At each iteration, output the current subscript and its value, then call $ORDER with -1 to get the previous subscript. Stop when $ORDER returns an empty string.

4. Predict the exact output

List the subscripts in reverse collating order along with their corresponding values. Ensure the output matches the exact format expected (e.g., subscript:value pairs).

5. Explain the termination condition

Clarify that the loop ends when $ORDER returns an empty string, indicating no previous subscript exists. This confirms the iteration covered all subscripts.

Key Points to Mention

Global variables in ObjectScript are sparse, multidimensional, and automatically sorted by subscript.
$ORDER with a direction argument of -1 returns the previous subscript in collating order.
The loop terminates when $ORDER returns an empty string, which happens when there is no previous subscript.
The output order is reverse collating order, which may differ from reverse insertion order.
Collating order for strings is case-sensitive and follows ASCII/Unicode order; numbers are sorted numerically.
The exact output depends on the initial data, so the candidate should trace carefully and state the output explicitly.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.