Dropbox Software Engineer Intern interview questions

They asked me to create a square root function.

Write a function called eval, which takes a string and returns a boolean. This string is allowed 6 different characters: 0, 1, &, |, (, and ). Eval should evaluate the string as a boolean expression, where 0 is false, 1 is true, & is an and, and | is an or. An example string might look like "(0 | (1 | 0)) & (1 & ((1 | 0) & 0))"