Clojure: how to avoid eval-ing the not-found expression in map get -


I have a map called "code> robots looking at the map, if given a robot by the given key If not present then I want to make one. not found RG is exactly the same as I want.

However, it seems that is not found expression is evaluated eagerly. How can I stop this assessment so that I can create a new robot, if someone is not present? 

  robot> (Def robot {1 {: name "R2D2"}}) # 'robot / robot robot & gt; (Get robot1) {: name "R2D2"} robot & gt; (Get robot 1 (printlane "fight it")) This (i.e. "R2D2"}    
 
 
 I agree completely, but if your map has incorrect or zero values, its implementation will not work.  
 Here's a more accurate solution:  
  (If robot 1 is included) (get robot 1) (printline "beep boop"))   
 and fancy macro:  
  (defmacro get-small [map key not found] `(map # ~ map key # key) (Includes # map # key included) (get the map # key # ~))   
 To eliminate the possibility of generating some side-effects again < Code> Walk , eg:  
  (lazy {1 false}} (printline "side effect") 1) (printlane "oh!")) < / Code>

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