getelm.cpp

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#include <../../nrnconf.h>
#include <stdlib.h>
#include <hocdec.h>
#include "lineq.h"
 
#define diag(s) hoc_execerror(s, (char*)0);
 
struct elm* getelm(struct elm* el, unsigned row, unsigned col)
   /* return pointer to row col element maintaining order in rows */
{
    struct elm *new_elem;
 
    if (el == ELM0)
        el = rowst[row];
    /*EMPTY*/
    if (el == ELM0);
    else if (el->col > col)
        el = ELM0;
    else
    {
        while ( el->c_right != ELM0 && el->c_right->col <= col)
            el = el->c_right;
        if (el->col == col)
            return(el);
    }
 
    if ( (new_elem = (struct elm *)malloc(sizeof(struct elm))) ==
        (struct elm *)0)
        diag("out of space for elements");
    new_elem->row = row;
    new_elem->col = col;
    new_elem->value = 0.;
    {
        new_elem->r_up = ELM0;  /* place new element first in column list */
        new_elem->r_down = colst[col];
        if (colst[col] != ELM0)
            colst[col]->r_up = new_elem;
        colst[col] = new_elem;
    }
    if (el == ELM0)     /* the new elm belongs at the beginning */
    {           /* of the row list */
        new_elem->c_left = ELM0;
        new_elem->c_right = rowst[row];
        if (rowst[row] != ELM0)
            rowst[row]->c_left = new_elem;
        rowst[row] = new_elem;
    }
    else            /* the new elm belongs after el */
    {
        new_elem->c_left = el;
        new_elem->c_right = el->c_right;
        el->c_right = new_elem;
        if (new_elem->c_right != ELM0)
            new_elem->c_right->c_left = new_elem;
    }
    return(new_elem);
}