dbkid - simple debugging facilities
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Simple debugging facilities.



This is not really a debugger, so it cannot be used to step through code executions.


This simple tool kit only offers a convenient way to capture values when running code.


This is not a perfect tool - it has its own limits. E.g. cannot capture binding Vars.


Please let me(xiejianming@gmail.com) know if you have anything (or bug report) to say....



There are three functions(well, they are macros actually) can help to investigate values during execution; and along with their own switches:

  • 'dbk' with switch of 'db' (debug)
  • '?' with switch of 'bp' (simplified 'dbk')
  • '??' a function to let you stop execution and query the runtime env.

We can use them in two scenarios:

  • to print values in code by using function 'dbk' or '?'
  • by using '??', we can stop execution at some point so that we can query the runtime env.

when using print functions, you can use

 ;; or

to turn off them - so that you can shut them up and it's safe to leave any 'dbk'/'?' in your code.

1 use dbkid.core


 (use 'dbkid.core)

2 use 'dbk' - a convenient printing function


 (let [x 123 y (range 10)]
    (dbk x y (map #(* % %) y))

then we will get:

 Debug: 2013-03-20 00:42:47 in NO_SOURCE_PATH@2: {x => 123, y => (0 1 2 3 4 5 6 7 ...), (map (fn* [p1__1420#] (* p1__1420# p1__1420#)) y) => (0 1 4 9 16 25 36 49 ...)}

2.1 turn off dbk

 (let [x 123 y (range 10)]
      (dbk x y (map #(* % %) y))

and now we get:

 DBK is now Disabled!

2.2 turn on dbk



it again....

3 use '?' - a simply put to print parameters

in most cases, it's tedious to always type 'dbk' clause to make a printing, and thus we offer '?': a simplified print function with a little adjustment on its functionality.

 (let [a 1 b 2 c (range 10)] (println a b c))

when we want to print values of a, b & c(or any of them), we can just put a question mark in front of 'println':

 (let [a 1 b 2 c (range 10)] (? println a b c))

check the result of above code in your REPL. If you find nothing, then try to turn it on by:


as 'db', 'bp' has similiar effect to '?'.

4 differences between 'dbk' and '?'

basically, they are the same but:

  • 'dbk' is of more free to print what you want but need more typing and construction in your code(just like inserting a 'print' in your code)
  • '?' is convenient but with limits:
    • it can be put only in front of a function call
    • it only prints parameter(s) given to that function

note that they both has a switch to turn on/off the printing function.

5 use '??' - an interactive "break-point"

Try following code:

 (def ^:dynamic xx 111111)
 (binding [xx "this is xx"]
   (let [a 123 b (defn tt[] (println a)) e [1 tt 3 (println 999)]]
      (let [a 789 c "wtf" d (range 11) f {1 2 3 (range 3) 4 (rand)} 
           g (fn [] (println "ggggggg")) h (def xxx 222222)]
        (println a) (println b) (println c)
        (println d) (println e) (println f)
        (println g) (println h)
        (?? println xx))))

when you see a promt, type instructions to find more(see below section).

5.1 '??' instructions

When you see a prompt, following instructions make '??' work its way:

  • '?' - print the current line info of break-point
  • 'l' - list locals
  • 'll' - list 'global'(within namespace) Vars
  • local/var name(e.g. 'a' in above example) - print the value of given local/var
  • normal clojure form(e.g. '(bp)' to turn '?' off in following executions) - eval the given form
  • ENTER - get through current break point

bonus: 'set-print-length' function to control length of a list's printing


 (set-print-length 5)

will sent printing of list to length of 5:

 Debug: 2013-03-25 20:56:18 in NO_SOURCE_PATH@863: {(range 10) => (0 1 2 3 4 ...)}
 (0 1 2 3 4 5 6 7 8 9)


Copyright (c) xjm (xiejianming@gmail.com). All rights reserved.

Distributed under the Eclipse Public License, the same as Clojure.