Although, strictly speaking, there is no largest positive
integer, the largest positive
integer which can be manipulated by
a68toc
is
2 147 483 647, and the
largest negative integer is
-2 147 483 647 (the first is
231 - 1 and the second is
-231 + 1). The representation of
a value in an Algol 68 program is called a
denotation because it denotes the value.
It is important to realise that the denotation of a
value is not the same as the value itself. To be precise, we say that
the denotation of a value represents an instance of
that value. For example, three separate instances of the value
denoted by the digits 31
occur in this paragraph. All
the instances denote the same value.
If you want to write the denotation of an integer in an Algol 68
program, you must use any of the digits 0
to 9
. No
signs are allowed. This means that you
cannot write denotations for negative integers in Algol 68 (but this
is not a problem as you will see). Although you cannot use commas or
decimal points, spaces can be inserted anywhere. Here are some
examples of denotations of integers separated by commas (the commas
are not part of the denotations):
0 , 3 , 03 , 3000000 , 2 147 483 647
Note that 3 and 03 denote the same value because the leading zero is not significant. However, the zeros in the three million are significant. The mode of each of the five denotations is INT. The following are incorrect denotations:
3,451 -2 1e6
The first contains a comma, the second is a formula, and the
third contains the letter e
. You will see later on that the
third expression denotes a number, but by definition this denotation
does not have mode INT
.
1,234,567
5.
-4
Sian Mountbatten 2012-01-19