Some typos we spotted in the book.
page 40 Figure 1.8: there should be two different gray shades among the rectangles. In the final print they might be too close to be distinguished.
page 47, head of section 2.5: the second abra should be aligned with the suffix of the string abracadabra above.
page 55: In the code of powerstring_by_find, the variables u and x should be the same.
page 115: the formula should be
page 143: the expression $\sum_{E_\ell}\ell$ should be instead $\sum \ell$, which stands for $\sum_{u\in U} \ell(u) + \sum_{v\in V} \ell(v)$.
page 213: Indeed, an integer y can be written -> any composite integer y
page 240, last line: suffix of t begn inning -> beginning