7.7
debug
source code: https://github.com/AlexKnauth/debug
A racket lang-extension for debugging, based on sugar/debug.
1 #lang debug
A lang-extension (like at-exp) that allows for quick debugging
shorthands to a program written in any racket-based language that looks at the
readtable.
To debug the value of an expression, simply put debug in front of the language at the top of the file (for instance #lang debug racket), and put #R, #RR or #RRR in front of the expression.
#R reports the value and returns it
#RR reports the value with a line number and returns it
#RRR reports the value with the file and line number, and returns it
Examples:
#lang debug racket (+ 1 2 #R(* 3 4)) ;(* 3 4) = 12 ;15
2 debug-repl
| (require debug/repl) | package: debug |
syntax
Creates a repl for debugging, which can access local variables in the context
where it is used.
(let ([x 1] [y 2]) (debug-repl))
Will be able to access the x and y local variables (if
debugging information is enabled in DrRacket’s
Choose Language window, or if the program was executed using
racket -l errortrace -t myprogram.rkt).
It becomes much more useful in a function definition:
(define (f x y) (debug-repl))
Then if you call (f 1 2), it will create a repl where x is
1 and y is 2.
In one of these repls, you can try evaluating different expressions. If you’re debugging a higher-order function for example, you can try out the functions it accepts or creates with multiple sets of arguments to see how they react.
procedure
(resume v ...) → any
v : any/c
When called inside of a debug-repl, exits the repl. The call to
debug-repl returns the arguments to resume.