octave: Numeric Data Types
4 Numeric Data Types
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A “numeric constant” may be a scalar, a vector, or a matrix, and it may
contain complex values.
The simplest form of a numeric constant, a scalar, is a single
number. Note that by default numeric constants are represented within
Octave by IEEE 754 double precision (binary64) floating-point format
(complex constants are stored as pairs of binary64 values). It is,
however, possible to represent real integers as described in 
Integer Data Types.
If the numeric constant is a real integer, it can be defined in
decimal, hexadecimal, or binary notation. Hexadecimal notation starts
with ‘0x’ or ‘0X’, binary notation starts with ‘0b’ or ‘0B’, otherwise
decimal notation is assumed. As a consequence, ‘0b’ is not a
hexadecimal number, in fact, it is not a valid number at all.
For better readability, digits may be partitioned by the underscore
separator ‘_’, which is ignored by the Octave interpreter. Here are
some examples of real-valued integer constants, which all represent the
same value and are internally stored as binary64:
42 # decimal notation
0x2A # hexadecimal notation
0b101010 # binary notation
0b10_1010 # underscore notation
round (42.1) # also binary64
In decimal notation, the numeric constant may be denoted as decimal
fraction or even in scientific (exponential) notation. Note that this
is not possible for hexadecimal or binary notation. Again, in the
following example all numeric constants represent the same value:
.105
1.05e-1
.00105e+2
Unlike most programming languages, complex numeric constants are
denoted as the sum of real and imaginary parts. The imaginary part is
denoted by a real-valued numeric constant followed immediately by a
complex value indicator (‘i’, ‘j’, ‘I’, or ‘J’ which represents ‘sqrt
(-1)’). No spaces are allowed between the numeric constant and the
complex value indicator. Some examples of complex numeric constants
that all represent the same value:
3 + 42i
3 + 42j
3 + 42I
3 + 42J
3.0 + 42.0i
3.0 + 0x2Ai
3.0 + 0b10_1010i
0.3e1 + 420e-1i
-- : double (X)
Convert X to double precision type.
See also: single XREFsingle.
-- : complex (X)
-- : complex (RE, IM)
Return a complex value from real arguments.
With 1 real argument X, return the complex result ‘X + 0i’.
With 2 real arguments, return the complex result ‘RE + IMi’.
‘complex’ can often be more convenient than expressions such as
‘a + b*i’. For example:
complex ([1, 2], [3, 4])
⇒ [ 1 + 3i 2 + 4i ]
DONTPRINTYET See also: real XREFreal, imag XREFimag, *noteDONTPRINTYET See also: real XREFreal, imag XREFimag,
iscomplex XREFiscomplex, abs XREFabs, arg XREFarg.
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