C *copy_cell(C *c) {
switch (c->type) {
case LABEL:
return makecell(LABEL, (V){ scpy(c->val.label) }, copy_cell(c->next));
case LIST:
return makecell(LIST, (V){ .list = copy_cell(c->val.list) }, copy_cell(c->next));
case BUILTIN:
return makecell(BUILTIN, (V){ .func = { scpy(c->val.func.name), c->val.func.addr} }, copy_cell(c->next));
Cell* parse(string sexpr)
{
// is_legal(sexpr);
// delete the whitesapce at the begining and end
// such that the first and last character are not white space
clearwhitespace(sexpr);
// if (sexpr.length() == 0) {
// return nil;
// }
if (sexpr.length() == 0) {
return nil;
}
if ( !is_legalexpr(sexpr)) {
return nil;
}
// check whether is single symbol
// i.e. leaf cell
// if (string::npos == sexpr.find('(')) {
if ('(' != sexpr[0]) {
// this is leaf cell
// bulid this leaf cell
Cell* root = makecell( sexpr );
return root;
}
// the first and last character are '(' and ')', respectively
// delete the two characters
int length = sexpr.size();
sexpr = sexpr.substr(1, length-2);
clearwhitespace(sexpr);
length = sexpr.size();
// if ( inparsecar ) {
// if (sexpr == "") {
// Cell* ec = new Cell("()");
// return ec;
// }
// }
// separate the s-expression into two left and right subsexps
Cell* root = separate_parse(sexpr);
return root;
}
