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0

rational number
Rational numbers are implemented by arbitrary precision integers
(bignum). A rational number is always expressed by a fraction of
lowest terms.
1

double precision floating point number (double float)
The numbers of this type are numbers provided by the computer hardware.
By default, when Asir is started, floating point numbers in a
ordinary form are transformed into numbers of this type. However,
they will be transformed into bigfloat numbers
when the switch bigfloat is turned on (enabled) by ctrl()
command.
[0] 1.2;
1.2
[1] 1.2e1000;
0
[2] ctrl("bigfloat",1);
1
[3] 1.2e1000;
1.20000000000000000513 E1000
A rational number shall be converted automatically into a double float
number before the operation with another double float number and the
result shall be computed as a double float number.
2

algebraic number
See section Algebraic numbers.
3

bigfloat
The bigfloat numbers of Asir is realized by PARI library.
A bigfloat number of PARI has an arbitrary precision mantissa
part. However, its exponent part admits only an integer with a single
word precision.
Floating point operations will be performed all in bigfloat after
activating the bigfloat switch by ctrl()
command.
The default precision is about 9 digits, which can be specified by
setprec()
command.
[0] ctrl("bigfloat",1);
1
[1] eval(2^(1/2));
1.414213562373095048763788073031
[2] setprec(100);
9
[3] eval(2^(1/2));
1.41421356237309504880168872420969807856967187537694807317654396116148
Function eval()
evaluates numerically its argument as far as
possible.
Notice that the integer given for the argument of setprec()
does
not guarantee the accuracy of the result,
but it indicates the representation size of numbers with which internal
operations of PARI are performed.
(See section eval
, deval
, section pari
.)
4

complex number
A complex number of Risa/Asir is a number with the form
a+b*@i
, where @i is the unit of imaginary number, and a
and b
are either a rational number, double float number or
bigfloat number, respectively.
The real part and the imaginary part of a complex number can be
taken out by real()
and imag()
respectively.
5

element of a small finite prime field
Here a small finite fieid means that its characteristic is less than
2^27.
At present small finite fields are used mainly
for groebner basis computation, and elements in such finite fields
can be extracted by taking coefficients of distributed polynomials
whose coefficients are in finite fields. Such an element itself does not
have any information about the field to which the element belongs, and
field operations are executed by using a prime p which is set by
setmod()
.
6

element of large finite prime field
This type expresses an element of a finite prime field whose characteristic
is an arbitrary prime. An object of this type is obtained by applying
simp_ff
to an integer.
7

element of a finite field of characteristic 2
This type expresses an element of a finite field of characteristic 2.
Let F be a finite field of characteristic 2. If [F:GF(2)]
is equal to n, then F is expressed as F=GF(2)[t]/(f(t)),
where f(t) is an irreducible polynomial over GF(2)
of degree n.
As an element g of GF(2)[t] can be expressed by a bit string,
An element g mod f in F can be expressed by two bit strings
representing g and f respectively.
Several methods to input an element of F are provided.

@
@
represents t mod f in F=GF(2)[t](f(t)).
By using @
one can input an element of F. For example
@^10+@+1
represents an element of F.

ptogf2n
ptogf2n
converts a univariate polynomial into an element of F.

ntogf2n
As a bit string, a nonnegative integer can be regarded as an element
of F. Note that one can input a nonnegative integer in decimal,
hexadecimal (0x
prefix) and binary (0b
prefix) formats.

micellaneous
simp_ff
is available if one wants to convert the whole
coefficients of a polynomial.
The characteristic of a large finite prime field and the defining
polynomial of a finite field of characteristic 2 are set by setmod_ff
.
Elements of finite fields do not have informations about the modulus.
Upon an arithmetic operation, the modulus set by setmod_ff
is
used. If one of the operands is a rational number, it is automatically
converted into an element of the finite field currently set and
the operation is done in the finite field.
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