5 ms·

Clojure from the ground-up: debugging

70 points by momo-reina 12y ago

lispm 12y ago
Error messages and stack traces look pretty ugly. In Common Lisp: CL-USER 51 > (bake (make-instance 'pie :flavor :blackberry) 375 10.25) Error: The value 3843.75 of #:|predicate1555| is not a predicate in CONDP. 1 (continue) Supply a new value of #:|predicate1555|. 2 (abort) Return to level 0. 3 Return to top loop level 0. A clear error message and a way to repair it. A stack frame: Call to BAKE {offset 394} PIE : #<PIE 402000993B> TEMP : 375 TIME : 10.25 DBG::|predicate| : 3843.75 DBG::|expression| : #<Function < 411007995C> DBG::G : 3843.75
- coldtea 12y ago
  Which CL is that?
  - lispm 12y ago
    LispWorks, the one Rich Hickey used for quite some time... ;-)
    - coldtea 12y ago
      Yeah, I feared that. That's the paid-for one, isn't it?
kaffeinecoma 12y ago
I'm trying so hard to love Clojure, but I keep running into examples of code like this in the world: http://imgur.com/79FlpTL http://imgur.com/79FlpTL. I don't write dense Lisp code like that, but unfortunately a lot of other people do. And I spend far more time reading code than writing it.
- harperlee 12y ago
  If you don't mind, what document is that?
  - kaffeinecoma 12y ago
    It's a page from the O'Reilly Clojure Programming book. I hate to point fingers at the authors, because it's generally a really great book. Just that some of the examples are rather dense, and I get the feeling that this is not at all unusual in the community.
  - raju 12y ago
    It's from Clojure Programming by Chas Emerick, Brian Carper, Christophe Grand - http://shop.oreilly.com/product/0636920013754.do http://shop.oreilly.com/product/0636920013754.do
- swannodette 12y ago
  Well that code seems pretty readable to me and appears to preserve some interesting properties of the original paper as mentioned below the source :) As far as spending more time reading Clojure than writing it I experience this myself - and I'm pretty sure this isn't a bad thing.
  - kaffeinecoma 12y ago
    I meant that in general, we as programmers will spend more time reading (our, others') code than writing it. Nature of the business. Did not mean to imply this was a bad thing. When I consider adopting a language, part of that consideration is how well I can read others' idiomatic code. It's so important for understanding libraries. I'm still just having a hard time with Clojure. I know it clicks for a lot of people though.
  - Flow 12y ago
    Perhaps readable if you read a lot of Clojure, but hardly anything that is easy to test piece by piece inspecting intermediate data, using a REPL for example.
swannodette 12y ago
Kyle's suggestions have a ton of value, but do note that debugging Clojure(Script) can also be a pedestrian activity if you so desire. All the usual mainstream bell/whistles IDE-based interactive debugging is available today in CursiveClojure - break on all exceptions, eval in frame, etc. Also ClojureScript has had accurate source mapping in Safari, Chrome, Firefox, and Node.js for quite a long time now and recently moved to support targets like iOS. It's a huge time saver even for an experienced Clojure programmer :)
- macmac 12y ago
  And if you favour open source IDEs the Eclipse based Counterclockwise http://doc.ccw-ide.org/ http://doc.ccw-ide.org/ will provide the same debugging experience for Clojure.
  - swannodette 12y ago
    My debugging experience with Counterclockwise wasn't very positive. But admittedly the last time I tried was a very long time ago and things may have changed significantly.
  - smrtinsert 12y ago
    I love ccw as a coding tool and the full editor repl is great too but I haven't been able to get breakpoints to work on it ever. Another thing that irks me about it lately is no real clojurescript support! That said it is still my primary clojure tool and things like figwheel help close the gap.
  - slantedview 12y ago
    I find debugging with Cursiveclojure to be easier.
lispm 12y ago
SBCL at compile time: * (defun bake (pie temp time) "Bakes a cake for a certain amount of time, returning a cake with a new :tastiness level." (setf (tastiness pie) (condp (* temp time) #'< (400 :burned) (350 :perfect) (300 :soggy)))) ; in: DEFUN BAKE ; (CONDP (* TEMP TIME) ; #'< ; (400 :BURNED) ; (350 :PERFECT) ; (300 :SOGGY)) ; ==> ; (LET ((#:PREDICATE2 (* TEMP TIME)) (#:EXPRESSION3 #'<)) ; (DECLARE (TYPE FUNCTION #:PREDICATE2)) ; (CHECK-TYPE #:PREDICATE2 FUNCTION "a predicate in CONDP") ; (COND ((FUNCALL #:PREDICATE2 #:EXPRESSION3 400) :BURNED) ; ((FUNCALL #:PREDICATE2 #:EXPRESSION3 350) :PERFECT) ; ((FUNCALL #:PREDICATE2 #:EXPRESSION3 300) :SOGGY))) ; ; caught WARNING: ; Derived type of (* TEMP TIME) is ; (VALUES NUMBER &OPTIONAL), ; conflicting with its asserted type ; FUNCTION. ; See also: ; The SBCL Manual, Node "Handling of Types" ; ; compilation unit finished ; caught 1 WARNING condition Pretty cool...
Flow 12y ago
Does anyone know what color theme those code boxes use? I apologize for being so shallow :)

70 points by momo-reina 12y ago

lispm 12y ago

Error messages and stack traces look pretty ugly. In Common Lisp: CL-USER 51 > (bake (make-instance 'pie :flavor :blackberry) 375 10.25) Error: The value 3843.75 of #:|predicate1555| is not a predicate in CONDP. 1 (continue) Supply a new value of #:|predicate1555|. 2 (abort) Return to level 0. 3 Return to top loop level 0. A clear error message and a way to repair it. A stack frame: Call to BAKE {offset 394} PIE : #<PIE 402000993B> TEMP : 375 TIME : 10.25 DBG::|predicate| : 3843.75 DBG::|expression| : #<Function < 411007995C> DBG::G : 3843.75

coldtea 12y ago
Which CL is that?
- lispm 12y ago
  LispWorks, the one Rich Hickey used for quite some time... ;-)
  - coldtea 12y ago
    Yeah, I feared that. That's the paid-for one, isn't it?

kaffeinecoma 12y ago

I'm trying so hard to love Clojure, but I keep running into examples of code like this in the world: http://imgur.com/79FlpTL http://imgur.com/79FlpTL. I don't write dense Lisp code like that, but unfortunately a lot of other people do. And I spend far more time reading code than writing it.

harperlee 12y ago
If you don't mind, what document is that?
- kaffeinecoma 12y ago
  It's a page from the O'Reilly Clojure Programming book. I hate to point fingers at the authors, because it's generally a really great book. Just that some of the examples are rather dense, and I get the feeling that this is not at all unusual in the community.
- raju 12y ago
  It's from Clojure Programming by Chas Emerick, Brian Carper, Christophe Grand - http://shop.oreilly.com/product/0636920013754.do http://shop.oreilly.com/product/0636920013754.do
swannodette 12y ago
Well that code seems pretty readable to me and appears to preserve some interesting properties of the original paper as mentioned below the source :) As far as spending more time reading Clojure than writing it I experience this myself - and I'm pretty sure this isn't a bad thing.
- kaffeinecoma 12y ago
  I meant that in general, we as programmers will spend more time reading (our, others') code than writing it. Nature of the business. Did not mean to imply this was a bad thing. When I consider adopting a language, part of that consideration is how well I can read others' idiomatic code. It's so important for understanding libraries. I'm still just having a hard time with Clojure. I know it clicks for a lot of people though.
- Flow 12y ago
  Perhaps readable if you read a lot of Clojure, but hardly anything that is easy to test piece by piece inspecting intermediate data, using a REPL for example.

swannodette 12y ago

Kyle's suggestions have a ton of value, but do note that debugging Clojure(Script) can also be a pedestrian activity if you so desire. All the usual mainstream bell/whistles IDE-based interactive debugging is available today in CursiveClojure - break on all exceptions, eval in frame, etc. Also ClojureScript has had accurate source mapping in Safari, Chrome, Firefox, and Node.js for quite a long time now and recently moved to support targets like iOS. It's a huge time saver even for an experienced Clojure programmer :)

macmac 12y ago
And if you favour open source IDEs the Eclipse based Counterclockwise http://doc.ccw-ide.org/ http://doc.ccw-ide.org/ will provide the same debugging experience for Clojure.
- swannodette 12y ago
  My debugging experience with Counterclockwise wasn't very positive. But admittedly the last time I tried was a very long time ago and things may have changed significantly.
- smrtinsert 12y ago
  I love ccw as a coding tool and the full editor repl is great too but I haven't been able to get breakpoints to work on it ever. Another thing that irks me about it lately is no real clojurescript support! That said it is still my primary clojure tool and things like figwheel help close the gap.
- slantedview 12y ago
  I find debugging with Cursiveclojure to be easier.

lispm 12y ago

SBCL at compile time: * (defun bake (pie temp time) "Bakes a cake for a certain amount of time, returning a cake with a new :tastiness level." (setf (tastiness pie) (condp (* temp time) #'< (400 :burned) (350 :perfect) (300 :soggy)))) ; in: DEFUN BAKE ; (CONDP (* TEMP TIME) ; #'< ; (400 :BURNED) ; (350 :PERFECT) ; (300 :SOGGY)) ; ==> ; (LET ((#:PREDICATE2 (* TEMP TIME)) (#:EXPRESSION3 #'<)) ; (DECLARE (TYPE FUNCTION #:PREDICATE2)) ; (CHECK-TYPE #:PREDICATE2 FUNCTION "a predicate in CONDP") ; (COND ((FUNCALL #:PREDICATE2 #:EXPRESSION3 400) :BURNED) ; ((FUNCALL #:PREDICATE2 #:EXPRESSION3 350) :PERFECT) ; ((FUNCALL #:PREDICATE2 #:EXPRESSION3 300) :SOGGY))) ; ; caught WARNING: ; Derived type of (* TEMP TIME) is ; (VALUES NUMBER &OPTIONAL), ; conflicting with its asserted type ; FUNCTION. ; See also: ; The SBCL Manual, Node "Handling of Types" ; ; compilation unit finished ; caught 1 WARNING condition Pretty cool...

Flow 12y ago

Does anyone know what color theme those code boxes use? I apologize for being so shallow :)