private IRegExNode <char> ParsePostfix()
{
var atom = this.ParseAtom();
if (this.Match('?'))
{
return(RegEx.Opt(atom));
}
if (this.Match('*'))
{
return(RegEx.Rep0(atom));
}
if (this.Match('+'))
{
return(RegEx.Rep1(atom));
}
if (this.Match('{'))
{
if (this.Match(','))
{
var atMost = this.ParseNumber();
this.Expect('}');
return(RegEx.AtMost(atMost, atom));
}
else
{
var atLeast = this.ParseNumber();
if (this.Match('}'))
{
return(RegEx.Exactly(atLeast, atom));
}
if (this.Match(','))
{
if (this.Match('}'))
{
return(RegEx.AtLeast(atLeast, atom));
}
var atMost = this.ParseNumber();
this.Expect('}');
return(RegEx.Between(atLeast, atMost, atom));
}
}
}
return(atom);
}
