# Dcons

Constants

The form of a numeric constant defined and illustrated in
Part I
is elaborated by the use of further letters, as in 2r3
for two-thirds, 2p1 for two π, and 2e3p1
for 2000 π.
The complete scheme of numeric constants obeys the following hierarchy:

 . The decimal point is obeyed first _ The negative sign is obeyed next e Exponential (scientific) notation ad ar j Complex (magnitude and angle) in degrees or radians; Complex number p x Numbers based on pi (o.1) and on Euler’s number (the exponential ^1) b Base value (using a to z for 10 to 35)

Moreover, digits with a trailing x denote an extended
precision integer, and digits followed by an r followed by
further digits denote a rational number.
See Section II G.

For example, 2.3 denotes two and three-tenths and _2.3
denotes its negation; but _2j3 denotes a complex number with
real part _2 and imaginary part 3 , not
the negation of the complex number 2j3 .
Furthermore, symbols at the same level of the hierarchy cannot be
used together: 1p2x3 is an ill-formed number.

The following lists illustrate the main points:

```   2.3e2 2.3e_2 2j3
230 0.023 2j3
2p1 1p_1
6.28319 0.31831
1x2 2x1 1x_1
7.38906 5.43656 0.367879