diff options
Diffstat (limited to 'Doc/library/decimal.rst')
| -rw-r--r-- | Doc/library/decimal.rst | 72 |
1 files changed, 42 insertions, 30 deletions
diff --git a/Doc/library/decimal.rst b/Doc/library/decimal.rst index f53c1f34670..10ddfa02b43 100644 --- a/Doc/library/decimal.rst +++ b/Doc/library/decimal.rst @@ -2,7 +2,7 @@ ===================================================================== .. module:: decimal - :synopsis: Implementation of the General Decimal Arithmetic Specification. + :synopsis: Implementation of the General Decimal Arithmetic Specification. .. moduleauthor:: Eric Price <eprice at tjhsst.edu> .. moduleauthor:: Facundo Batista <facundo at taniquetil.com.ar> @@ -121,7 +121,7 @@ reset them before monitoring a calculation. .. _decimal-tutorial: -Quick-start Tutorial +Quick-start tutorial -------------------- The usual start to using decimals is importing the module, viewing the current @@ -1096,40 +1096,52 @@ In addition to the three supplied contexts, new contexts can be created with the default values are copied from the :const:`DefaultContext`. If the *flags* field is not specified or is :const:`None`, all flags are cleared. - *prec* is an integer in the range [``1``, :const:`MAX_PREC`] that sets - the precision for arithmetic operations in the context. + .. attribute:: prec - The *rounding* option is one of the constants listed in the section - `Rounding Modes`_. + An integer in the range [``1``, :const:`MAX_PREC`] that sets + the precision for arithmetic operations in the context. - The *traps* and *flags* fields list any signals to be set. Generally, new - contexts should only set traps and leave the flags clear. + .. attribute:: rounding - The *Emin* and *Emax* fields are integers specifying the outer limits allowable - for exponents. *Emin* must be in the range [:const:`MIN_EMIN`, ``0``], - *Emax* in the range [``0``, :const:`MAX_EMAX`]. + One of the constants listed in the section `Rounding Modes`_. - The *capitals* field is either ``0`` or ``1`` (the default). If set to - ``1``, exponents are printed with a capital ``E``; otherwise, a - lowercase ``e`` is used: ``Decimal('6.02e+23')``. + .. attribute:: traps + flags - The *clamp* field is either ``0`` (the default) or ``1``. - If set to ``1``, the exponent ``e`` of a :class:`Decimal` - instance representable in this context is strictly limited to the - range ``Emin - prec + 1 <= e <= Emax - prec + 1``. If *clamp* is - ``0`` then a weaker condition holds: the adjusted exponent of - the :class:`Decimal` instance is at most :attr:`~Context.Emax`. When *clamp* is - ``1``, a large normal number will, where possible, have its - exponent reduced and a corresponding number of zeros added to its - coefficient, in order to fit the exponent constraints; this - preserves the value of the number but loses information about - significant trailing zeros. For example:: + Lists of any signals to be set. Generally, new contexts should only set + traps and leave the flags clear. - >>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999') - Decimal('1.23000E+999') + .. attribute:: Emin + Emax - A *clamp* value of ``1`` allows compatibility with the - fixed-width decimal interchange formats specified in IEEE 754. + Integers specifying the outer limits allowable for exponents. *Emin* must + be in the range [:const:`MIN_EMIN`, ``0``], *Emax* in the range + [``0``, :const:`MAX_EMAX`]. + + .. attribute:: capitals + + Either ``0`` or ``1`` (the default). If set to + ``1``, exponents are printed with a capital ``E``; otherwise, a + lowercase ``e`` is used: ``Decimal('6.02e+23')``. + + .. attribute:: clamp + + Either ``0`` (the default) or ``1``. If set to ``1``, the exponent ``e`` + of a :class:`Decimal` instance representable in this context is strictly + limited to the range ``Emin - prec + 1 <= e <= Emax - prec + 1``. + If *clamp* is ``0`` then a weaker condition holds: the adjusted exponent of + the :class:`Decimal` instance is at most :attr:`~Context.Emax`. When *clamp* is + ``1``, a large normal number will, where possible, have its + exponent reduced and a corresponding number of zeros added to its + coefficient, in order to fit the exponent constraints; this + preserves the value of the number but loses information about + significant trailing zeros. For example:: + + >>> Context(prec=6, Emax=999, clamp=1).create_decimal('1.23e999') + Decimal('1.23000E+999') + + A *clamp* value of ``1`` allows compatibility with the + fixed-width decimal interchange formats specified in IEEE 754. The :class:`Context` class defines several general purpose methods as well as a large number of methods for doing arithmetic directly in a given context. @@ -1769,7 +1781,7 @@ The following table summarizes the hierarchy of signals:: .. _decimal-notes: -Floating-Point Notes +Floating-point notes -------------------- |