# Revision history [back]

Hi,

It depends. You have the choice or using the Cython variable as follows

from sage.rings.real_mpfr cimport RealNumber
from sage.rings.real_mpfr import RR

cdef RealNumber my_number = RR(4)
...


Or you can use pure C as follows

cdef mpfr_t value
...


It might help to have a look at how the real number are implemented in Sage in the files

• $SAGE_ROOT/devel/sage-main/sage/rings/real_mpfr.pyx • $SAGE_ROOT/devel/sage-main/sage/rings/real_mpfr.pxd

Hi,

It depends. You have the choice or of using the a Cython variable as follows

from sage.rings.real_mpfr cimport RealNumber
from sage.rings.real_mpfr import RR

cdef RealNumber my_number = RR(4)
RR(5.634)
...


Or you can use pure C as follows

cdef mpfr_t value
mpfr_init2(value, 53)
mpfr_set_flt(value, 5.364, MPFR_RNDN)
...


Anyway, in the latter case, it is not possible to write value = 5 because there is no cast from int to mpfr_t (those are C variables)!

It might help to have a look at how the real number are implemented in Sage in the files

• $SAGE_ROOT/devel/sage-main/sage/rings/real_mpfr.pyx • $SAGE_ROOT/devel/sage-main/sage/rings/real_mpfr.pxd