void Expr::Parse(void) {
Expr *e = AllocExpr();
e->op = ALL_RESOLVED;
PushOperator(e);
for(;;) {
Expr *n = Next();
if(!n) throw "end of expression unexpected";
if(n->op == CONSTANT) {
PushOperand(n);
Consume();
} else if(n->op == PAREN && n->c == '(') {
Consume();
Parse();
n = Next();
if(n->op != PAREN || n->c != ')') throw "expected: )";
Consume();
} else if(n->op == UNARY_OP) {
PushOperator(n);
Consume();
continue;
} else if(n->op == BINARY_OP && n->c == '-') {
// The minus sign is special, because it might be binary or
// unary, depending on context.
n->op = UNARY_OP;
n->c = 'n';
PushOperator(n);
Consume();
continue;
} else {
throw "expected expression";
}
n = Next();
if(n && n->op == BINARY_OP) {
ReduceAndPush(n);
Consume();
} else {
break;
}
}
while(TopOperator()->op != ALL_RESOLVED) {
Reduce();
}
PopOperator(); // discard the ALL_RESOLVED marker
}
void Expr::ReduceAndPush(Expr *n) {
while(Precedence(n) <= Precedence(TopOperator())) {
Reduce();
}
PushOperator(n);
}
/**
* Function ReadParam
* Read one aperture macro parameter
* a parameter can be:
* a number
* a reference to an aperture definition parameter value: $1 ot $3 ...
* a parameter definition can be complex and have operators between numbers and/or other parameter
* like $1+3 or $2x2..
* Note minus sign is not always an operator. It can be the sign of a value.
* Parameters are separated by a comma ( of finish by *)
* @param aText = pointer to the parameter to read. Will be modified to point to the next field
* @return true if a param is read, or false
*/
bool AM_PARAM::ReadParam( char*& aText )
{
bool found = false;
int ivalue;
double dvalue;
bool end = false;
while( !end )
{
switch( *aText )
{
case ',':
aText++;
// fall through
case 0: // EOL
case '*': // Terminator in a gerber command
end = true;
break;
case ' ':
aText++;
break;
case '$':
// defered value defined later, in ADD command which define defered parameters
++aText;
ivalue = ReadInt( aText, false );
if( m_index < 1 )
SetIndex( ivalue );
PushOperator( PUSHPARM, ivalue );
found = true;
break;
case '/':
PushOperator( DIV );
aText++;
break;
case 'x':
case 'X':
PushOperator( MUL );
aText++;
break;
case '-':
case '+':
// Test if this is an operator between 2 params, or the sign of a value
if( m_paramStack.size() > 0 && !m_paramStack.back().IsOperator() )
{ // Seems an operator
PushOperator( *aText == '+' ? ADD : SUB );
aText++;
}
else
{ // seems the sign of a value
dvalue = ReadDouble( aText, false );
PushOperator( PUSHVALUE, dvalue );
found = true;
}
break;
case '=': // A local definition found like $4=$3/2
// At this point, one defered parameter is expected to be read.
// this parameter value (the index) is stored in m_index.
// The list of items is cleared
aText++;
m_paramStack.clear();
found = false;
break;
default:
dvalue = ReadDouble( aText, false );
PushOperator( PUSHVALUE, dvalue );
found = true;
break;
}
}
return found;
}
