HEADER

Function: _header_programming/control
Class: header
Section: programming/control
Doc:
 \section{Programming in GP: control statements}
 \sidx{programming}\label{se:programming}

   A number of control statements are available in GP. They are simpler and
 have a syntax slightly different from their C counterparts, but are quite
 powerful enough to write any kind of program. Some of them are specific to
 GP, since they are made for number theorists. As usual, $X$ will denote any
 simple variable name, and \var{seq} will always denote a sequence of
 expressions, including the empty sequence.

 \misctitle{Caveat} In constructs like
 \bprog
     for (X = a,b, seq)
 @eprog\noindent
 the variable \kbd{X} is lexically scoped to the loop, leading to possibly
 unexpected behavior:
 \bprog
     n = 5;
     for (n = 1, 10,
       if (something_nice(), break);
     );
     \\ @com at this point \kbd{n} is 5 !
 @eprog\noindent
 If the sequence \kbd{seq} modifies the loop index, then the loop
 is modified accordingly:
 \bprog
     ? for (n = 1, 10, n += 2; print(n))
     3
     6
     9
     12
 @eprog

Function: _header_programming/specific
Class: header
Section: programming/specific
Doc:
 \section{Programming in GP: other specific functions}
 \label{se:gp_program}

   In addition to the general PARI functions, it is necessary to have some
 functions which will be of use specifically for \kbd{gp}, though a few of these
 can be accessed under library mode. Before we start describing these, we recall
 the difference between \emph{strings} and \emph{keywords} (see
 \secref{se:strings}): the latter don't get expanded at all, and you can type
 them without any enclosing quotes. The former are dynamic objects, where
 everything outside quotes gets immediately expanded.


Function: _header_programming/parallel
Class: header
Section: programming/parallel
Doc:
 \section{Parallel programming}

 These function are only available if PARI was configured using
 \kbd{Configure --mt=\dots}. Two multithread interfaces are supported:

 \item POSIX threads

 \item Message passing interface (MPI)

 As a rule, POSIX threads are well-suited for single systems, while MPI is used
 by most clusters. However the parallel GP interface does not depend on the
 chosen multithread interface: a properly written GP program will work
 identically with both.