/*-
*-----------------------------------------------------------------------
* CondF --
* Parse a conjunctive factor (nice name, wot?)
* F -> T && F | T
*
* Results:
* True, False or Err
*
* Side Effects:
* Tokens are consumed.
*-----------------------------------------------------------------------
*/
static Token
CondF(bool doEval)
{
Token l, o;
l = CondT(doEval);
if (l != Err) {
o = CondToken(doEval);
if (o == And) {
/* F -> T && F
*
* If T is False, the whole thing will be False, but we
* have to parse the r.h.s. anyway (to throw it away). If
* T is True, the result is the r.h.s., be it an Err or no.
* */
if (l == True)
l = CondF(doEval);
else
(void)CondF(false);
} else
/* F -> T. */
condPushBack = o;
}
return l;
}
/*-
*-----------------------------------------------------------------------
* CondF --
* Parse a conjunctive factor (nice name, wot?)
* F -> T && F | T
*
* Results:
* TOK_TRUE, TOK_FALSE or TOK_ERROR
*
* Side Effects:
* Tokens are consumed.
*
*-----------------------------------------------------------------------
*/
static Token
CondF(Boolean doEval)
{
Token l, o;
l = CondT(doEval);
if (l != TOK_ERROR) {
o = CondToken(doEval);
if (o == TOK_AND) {
/*
* F -> T && F
*
* If T is TOK_FALSE, the whole thing will be TOK_FALSE, but we have to
* parse the r.h.s. anyway (to throw it away).
* If T is TOK_TRUE, the result is the r.h.s., be it an TOK_ERROR or no.
*/
if (l == TOK_TRUE) {
l = CondF(doEval);
} else {
(void)CondF(FALSE);
}
} else {
/*
* F -> T
*/
CondPushBack(o);
}
}
return (l);
}
/*-
*-----------------------------------------------------------------------
* CondE --
* Main expression production.
* E -> F || E | F
*
* Results:
* True, False or Err.
*
* Side Effects:
* Tokens are, of course, consumed.
*-----------------------------------------------------------------------
*/
static Token
CondE(bool doEval)
{
Token l, o;
l = CondF(doEval);
if (l != Err) {
o = CondToken(doEval);
if (o == Or) {
/* E -> F || E
*
* A similar thing occurs for ||, except that here we
* make sure the l.h.s. is False before we bother to
* evaluate the r.h.s. Once again, if l is False, the
* result is the r.h.s. and once again if l is True, we
* parse the r.h.s. to throw it away. */
if (l == False)
l = CondE(doEval);
else
(void)CondE(false);
} else
/* E -> F. */
condPushBack = o;
}
return l;
}
/*-
*-----------------------------------------------------------------------
* CondE --
* Main expression production.
* E -> F || E | F
*
* Results:
* TOK_TRUE, TOK_FALSE or TOK_ERROR.
*
* Side Effects:
* Tokens are, of course, consumed.
*
*-----------------------------------------------------------------------
*/
static Token
CondE(Boolean doEval)
{
Token l, o;
l = CondF(doEval);
if (l != TOK_ERROR) {
o = CondToken(doEval);
if (o == TOK_OR) {
/*
* E -> F || E
*
* A similar thing occurs for ||, except that here we make sure
* the l.h.s. is TOK_FALSE before we bother to evaluate the r.h.s.
* Once again, if l is TOK_FALSE, the result is the r.h.s. and once
* again if l is TOK_TRUE, we parse the r.h.s. to throw it away.
*/
if (l == TOK_FALSE) {
l = CondE(doEval);
} else {
(void)CondE(FALSE);
}
} else {
/*
* E -> F
*/
CondPushBack(o);
}
}
return (l);
}
