void define()
{
register int start_token; /* the 1st token in the function definition */
register struct udvt_entry *udv;
register struct udft_entry *udf;
if (equals(c_token + 1, "(")) {
/* function ! */
int dummy_num = 0;
struct at_type *at_tmp;
char save_dummy[MAX_NUM_VAR][MAX_ID_LEN + 1];
memcpy(save_dummy, c_dummy_var, sizeof(save_dummy));
start_token = c_token;
do {
c_token += 2; /* skip to the next dummy */
copy_str(c_dummy_var[dummy_num++], c_token, MAX_ID_LEN);
} while (equals(c_token + 1, ",") && (dummy_num < MAX_NUM_VAR));
if (equals(c_token + 1, ","))
int_error("function contains too many parameters", c_token + 2);
c_token += 3; /* skip (, dummy, ) and = */
if (END_OF_COMMAND)
int_error("function definition expected", c_token);
udf = dummy_func = add_udf(start_token);
if ((at_tmp = perm_at()) == (struct at_type *) NULL)
int_error("not enough memory for function", start_token);
if (udf->at) /* already a dynamic a.t. there */
free((char *) udf->at); /* so free it first */
udf->at = at_tmp; /* before re-assigning it. */
memcpy(c_dummy_var, save_dummy, sizeof(save_dummy));
m_capture(&(udf->definition), start_token, c_token - 1);
dummy_func = NULL; /* dont let anyone else use our workspace */
} else {
/* variable ! */
start_token = c_token;
c_token += 2;
udv = add_udv(start_token);
(void) const_express(&(udv->udv_value));
udv->udv_undef = FALSE;
}
}
/*
* Syntax: set link {x2|y2} {via <expression1> inverse <expression2>}
* Create action code tables for the functions linking primary and secondary axes.
* expression1 maps primary coordinates into the secondary coordinate space.
* expression2 maps secondary coordinates into the primary coordinate space.
*/
void
parse_link_via( struct udft_entry *udf )
{
int start_token;
/* Caller left us pointing at "via" or "inverse" */
c_token++;
start_token = c_token;
if (END_OF_COMMAND)
int_error(c_token,"Missing expression");
/* Save action table for the linkage mapping */
strcpy(c_dummy_var[0], "x");
strcpy(c_dummy_var[1], "y");
dummy_func = udf;
free_at(udf->at);
udf->at = perm_at();
dummy_func = NULL;
/* Save the mapping expression itself */
m_capture(&(udf->definition), start_token, c_token - 1);
}
/* create action code for 'sum' expressions */
static void
parse_sum_expression()
{
/* sum [<var>=<range>] <expr>
* - Pass a udf to f_sum (with action code (for <expr>) that is not added
* to the global action table).
* - f_sum uses a newly created udv (<var>) to pass the current value of
* <var> to <expr> (resp. its ac).
* - The original idea was to treat <expr> as function f(<var>), but there
* was the following problem: Consider 'g(x) = sum [k=1:4] f(k)'. There
* are two dummy variables 'x' and 'k' from different functions 'g' and
* 'f' which would require changing the parsing of dummy variables.
*/
char *errormsg = "Expecting 'sum [<var> = <start>:<end>] <expression>'\n";
char *varname = NULL;
union argument *arg;
struct udft_entry *udf;
struct at_type * save_at;
int save_at_size;
int i;
/* Caller already checked for string "sum [" so skip both tokens */
c_token += 2;
/* <var> */
if (!isletter(c_token))
int_error(c_token, errormsg);
/* create a user defined variable and pass it to f_sum via PUSHC, since the
* argument of f_sum is already used by the udf */
m_capture(&varname, c_token, c_token);
add_udv(c_token);
arg = add_action(PUSHC);
Gstring(&(arg->v_arg), varname);
c_token++;
if (!equals(c_token, "="))
int_error(c_token, errormsg);
c_token++;
/* <start> */
parse_expression();
if (!equals(c_token, ":"))
int_error(c_token, errormsg);
c_token++;
/* <end> */
parse_expression();
if (!equals(c_token, "]"))
int_error(c_token, errormsg);
c_token++;
/* parse <expr> and convert it to a new action table. */
/* modeled on code from temp_at(). */
/* 1. save environment to restart parsing */
save_at = at;
save_at_size = at_size;
at = NULL;
/* 2. save action table in a user defined function */
udf = (struct udft_entry *) gp_alloc(sizeof(struct udft_entry), "sum");
udf->next_udf = (struct udft_entry *) NULL;
udf->udf_name = NULL; /* TODO maybe add a name and definition */
udf->at = perm_at();
udf->definition = NULL;
udf->dummy_num = 0;
for (i = 0; i < MAX_NUM_VAR; i++)
(void) Ginteger(&(udf->dummy_values[i]), 0);
/* 3. restore environment */
at = save_at;
at_size = save_at_size;
/* pass the udf to f_sum using the argument */
add_action(SUM)->udf_arg = udf;
}