I'm still working on wrapping the computer algebra package LiE in
cython. For those unfamiliar, LiE is basically it's own language,
written in C. And I'm interested in calling some of the math-heavy
functions, but bypassing the interpreter.
Error checking is sprinkled throughout the LiE source, for instance:
matrix *mat_mul_mat_mat(matrix *a, matrix *b) {
if (a->ncols != b->nrows)
error("Number columns arg1 unequal number of rows arg2 .\n");
return Matmult(a, b);
}
When an error is found, LiE calls the error() function, which prints
out a traceback, cleans up a little bit, and finally does a longjump
to "envbuf," which is at the beginning of the interpreter loop:
void error(char *format, ...)
{
symblst list;
extern jmp_buf envbuf;
va_list ap;
va_start(ap, format);
vfprintf(stderr, format, ap);
if (am_monitor) vfprintf(monfile, format, ap);
if (label->name)
{
boolean printin = (label->name != seq_name);
if (printin)
Printf("(in %s",name_tab[label->name]);
if (no_terminal(cur_in) || strcmp(label->fname, "stdin")!=0) {
if (!printin) Printf("(");
Printf(" at line %d of file %s)\n",label->line, label-
>fname);
}
else
if (printin) Printf(")\n");
}
if (fun_name)
Printf("[in function %s ]\n", name_tab[fun_name]);
for (list = top_definitions; list!=NULL; list = list->next)
/* Recover symbol table */
{ if (list->class == FUNCTION_COPIED) list->class = FUNCTION;
if (list->next && list->next->class == DUMMY)
list->next = list->next->next; /* Remove sym */
}
if (repair_obj) {
setshared(repair_obj);
repair_obj = (object) NULL;
}
if (cur_in==stdin)
clear_input();
else
do exit_input_file(parsing); while (cur_in!=stdin); /* pop
input files */
longjmp(envbuf, -1);
}
Instead of doing all this stuff, and longjumping to the LiE
interpreter, I'd like to raise a python exception that could be caught
by whatever cython function called "mat_mul_mat_mat." Does anyone
have any advice on how to do this? I took a look at the python
exception portion of the C/API. It seems like I might want to make a
C file with my own error function:
error(char* format, ...) {
turn format into a string
PyErr_SetString(errorstring)
longjump somewhere ???
}
and then comment out the error function in the LiE source... but I'm
not totally sure how to put it all together. Also, If it's possible,
I'd like to avoid modifying the LiE source too much -- i.e. commenting
out an entire function. I'm not a C master, so I wouldn't be
surprised if I've missed an obvious way to do this.
Thanks for the advice!
David
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