int
expression(void)
{
int value = 0;
char op = 0, ch = 0;
skip_space();
ch = str[idx];
if (ch == '\0') {
return 0;
}
if (ch == '(') {
idx += 1; /* read '(' */
value = expression();
skip_space();
idx += 1; /* read ')' */
skip_space();
if (is_operator()) {
op = operator();
/*printf("%d|%c ", order++, op);*/
int v = expression();
return do_num(op, value, v);
} else {
return value;
}
} else if (ch == '_' || isdigit(ch)) {
int num = number();
/*printf("%d|%d ", order++, num);*/
skip_space();
if (is_operator()) {
op = operator();
/*printf("%d|%c ", order++, op);*/
value = expression();
return do_num(op, num, value);
} else {
return num;
}
} else {
char var = variable();
/*printf("%d|%c ", order++, var);*/
skip_space();
if (is_operator()) {
op = operator();
/*printf("%d|%c ", order++, op);*/
value = expression();
return do_var(op, var, value);
} else {
return vars[var - 'A'];
}
}
}
int
do_var(char op, char var, int num)
{
int i = var - 'A';
switch (op) {
case '=':
vars[i] = num;
return num;
default:
return do_num(op, vars[i], num);
}
}
static int make_toks(const char *source, int *my_token) {
int old_tok = STARTTOK, tok_in = 0;
int index = 0, nparen = 0, lastindex = 0;
while (source[index] != '\0') {
int token = find_tok(&my_symb, source + index);
lastindex = index;
if (token != my_symb.len)
index += my_symb.elems[token].len;
if ((token == MINUS) &&
((old_tok == STARTTOK) || (old_tok == COMMA) || (old_tok == LPAREN)))
token = NEGATE;
else if (token == LPAREN)
++nparen;
else if (token == RPAREN)
--nparen;
if (token == my_symb.len) {
char num[40];
double value;
/* WARNING -- ASSUMES 32 bit int and 64 bit double */
union {
struct {
int int1;
int int2;
} pieces;
struct {
double z;
} num;
} encoder;
if (do_num(source, num, &value, &index)) {
plintf("illegal expression: %s\n", num);
show_where(source, index);
return (1);
}
/* new code 3/95 */
encoder.num.z = value;
my_token[tok_in++] = NUMTOK;
my_token[tok_in++] = encoder.pieces.int1;
my_token[tok_in++] = encoder.pieces.int2;
if (check_syntax(old_tok, NUMTOK) == 1) {
plintf("Illegal syntax \n");
show_where(source, lastindex);
return (1);
}
old_tok = NUMTOK;
} else {
my_token[tok_in++] = token;
if (check_syntax(old_tok, token) == 1) {
plintf("Illegal syntax (Ref:%d %d) \n", old_tok, token);
show_where(source, lastindex);
tokeninfo(old_tok);
tokeninfo(token);
return (1);
}
old_tok = token;
}
}
my_token[tok_in++] = ENDTOK;
if (check_syntax(old_tok, ENDTOK) == 1) {
plintf("Premature end of expression \n");
show_where(source, lastindex);
return (1);
}
if (nparen != 0) {
plintf("parentheses don't match\n");
return (1);
}
return (0);
}
