Dedication

Those who are enamored of practice without theory are like a pilot who goes into a ship without rudder or compass and never has any certainty where he is going Practice should always be based upon a sound knowledge of theory.

—Leonardo da Vinci (1452–1519)

The trouble with people is not that they don’t know but that they know so much that ain’t so.

—Josh Billings (1818–1885)

Languages die... mathematical ideas do not.

—G. H. Hardy (1877–1947)

Unfortunately, the gap between theory and practice is not as wide in theory as it is in practice.

—Anon.

These are my principles. If you don’t like them, I have others.

—Groucho Marx (1890–1977)

There is no royal road to geometry.

—Euclid (c. 365–275 BCE), attrib.

To all those who think an exercise like this one is worthwhile, and in particular to the memory of Lex de Haan, who is very much missed

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