Hi Daniel, Thank you for your email.
In nutshell: how can I check whether a property map has some given key?
Some property maps may provide bounds checking, but the property map concept doesn't require it, so in general you can't.
Good to know. I didn't find this in the property map documentation.
I think you'll need to give every edge a lambda number, but you might reserve a special value to indicate that the lambda property isn't applicable to that edge.
I had the class def_int as the type of the lambda property: struct def_int { int value; def_int() : value(-1) {} def_int & operator = (int a) { value = a; } bool operator < (const def_int &a) { return value < a.value; } }; In this way if a link doesn't have this property, then the property map has -1 for that edge. The problem is that I needed to define operators =, <, <<, >> to make it work. Then I wanted to use some other stuff and got cryptic error messages at compilation. Finally I dropped the def_int class in favor of the int type, and now I make sure that every link in the .dot file has a lambdas property. Best, Irek