These first four chapters make up Part 1 of this book. In later chapters we will take up again themes which are introduced in Part 1. The user types a line at the keyboard. The prompt is seen by the cursor being positioned a few spaces from the left margin. Thus in this book, a line indented by a few spaces represents input typed by a user, and a following line, not indented, represents the corresponding output.
Spaces can make an expression more readable.
The next example shows how a negative number is represented. The left argument is 2 and the right argument is 3 . Sometimes we may wish to repeat the same computation several times for several different numbers. Sometimes it is helpful, when we are looking at a new function, to see how a pattern in a list of arguments gives rise to a pattern in the list of results. For example, when 7 is divided by 2 we can say that the quotient is 3 and the remainder is 1 .