Function: _def_compatible
Class: default
Section: default
C-Name: sd_compatible
Prototype:
Help:
Doc: The GP function names and syntax
 have changed tremendously between versions 1.xx and 2.00. To help you cope
 with this we provide some kind of backward compatibility, depending on the
 value of this default:

 \quad \kbd{compatible} = 0: no backward compatibility. In this mode, a very
 handy function, to be described in \secref{se:whatnow}, is \kbd{whatnow},
 which tells you what has become of your favorite functions, which \kbd{gp}
 suddenly can't seem to remember.

 \quad \kbd{compatible} = 1: warn when using obsolete functions, but
 otherwise accept them. The output uses the new conventions though, and
 there may be subtle incompatibilities between the behavior of former and
 current functions, even when they share the same name (the current function
 is used in such cases, of course!). We thought of this one as a transitory
 help for \kbd{gp} old-timers. Thus, to encourage switching to \kbd{compatible}=0,
 it is not possible to disable the warning.

 \quad \kbd{compatible} = 2: use only the old function naming scheme (as
 used up to version 1.39.15), but \emph{taking case into account}. Thus
 \kbd{I} (${}=\sqrt{-1}$) is not the same as \kbd{i} (user variable, unbound
 by default), and you won't get an error message using \kbd{i} as a loop
 index as used to be the case.

 \quad \kbd{compatible} = 3: try to mimic exactly the former behavior. This
 is not always possible when functions have changed in a fundamental way.
 But these differences are usually for the better (they were meant to,
 anyway), and will probably not be discovered by the casual user.

 One adverse side effect is that any user functions and aliases that have
 been defined \emph{before} changing \kbd{compatible} will get erased if this
 change modifies the function list, i.e.~if you move between groups
 $\{0,1\}$ and $\{2,3\}$ (variables are unaffected). We of course strongly
 encourage you to try and get used to the setting \kbd{compatible}=0.

 Note that the default \tet{new_galois_format} is another compatibility setting,
 which is completely independent of \kbd{compatible}.

 The default value is \kbd{0}.
