From a design perspective, some other choices are questionable; for example, the use of Strings to hold the operators opens up the possibility of small typos leading to erroneous results.

She insisted that, to allow proper sorting, the incoming data stream should try to keep track of the end of leading articles in title strings.

The way hashcash poses a challenge is by asking "minters" to produce strings (stamps) that when hashed with the Secure Hash Algorithm, SHA-1, have a number of leading zeros in their hash.