lt1170 circuit
You can try to make a buck converter from many ICs, you can find even application circuits utilizing a linear voltage regulator. But a LT1170 is really bad suited for this purpose, I think, there are more pleasant ways to waste your time. Apart from this, the said Linear application should be hopefully operational somehow.
The "r" symbol sems to be a curious creation of Linear application engineers, designating a small resistor, possibly trace resistances. If you want to know more, file a support request to Linear! There may be a problem, if the author isn't working with Linear any more, cause it's a rather old application, copied from a more than 20 years old LT1070 datasheet.
P.S.: I see, that the shorted resistor symbol is used in some other schematics, too. So it may be considered well-known, the resistance value is mssing from the schematics anyway.