18 Debugging tools

(require (planet untyped/unlib/debug))

Utilities for printing the runtime values of variables for debugging purposes, with minimal disruption to code structure.

(debug-enabled?) → boolean?

(debug-enabled? val) → void?

val : boolean?

Boolean parameter for enabling or disabling the printing of debugging information. Defaults to #t.

(current-debug-printer) → (-> string? any void?)

(current-debug-printer proc) → void?

proc : (-> string? any void?)

Parameter controlling the formatting of printed debugging information. Value must be a procedure that takes a message and a value and returns void. The default value prints the message and a colon on one line and pretty-prints the value (slightly indented) on subsequent lines.

(debug val) → any

val : any

Prints val and returns it transparently.

Examples:

> (length (debug "message" (make-list 5 (iota 10))))

message:     ((0 1 2 3 4 5 6 7 8 9)      (0 1 2 3 4 5 6 7 8 9)      (0 1 2 3 4 5 6 7 8 9)      (0 1 2 3 4 5 6 7 8 9)      (0 1 2 3 4 5 6 7 8 9))

5

(debug* proc arg ...) → any

proc : procedure?

arg : any

Applies proc to args and prints and returns the return value transparently.

Examples:

> (debug* "message" * 2 2)

message:     4

4

(define-debug id expr)

Expands to a define form that prints the value of id as a side effect.

Examples:

> (define-debug test-data       (+ 1 2 3))

test-data:     6

(let-debug ([id expr] ...) expr ...)

Expands to a let form that prints the value of each id as it is assigned.

Examples:

> (let-debug ([a (+ 1 2)]                 [b (+ 3 4)])        b)

a:     3   b:     7

7

(let*-debug ([id expr] ...) expr ...)

Expands to a let* form that prints the value of each id as it is assigned.

Examples:

> (let*-debug ([a (+ 1 2)]                  [b (* b b)])        b)

a:     3

reference to undefined identifier: b

(letrec-debug ([id expr] ...) expr ...)

Expands to a letrec form that prints the value of each id as it is assigned.

Examples:

> (let-debug ([a (+ 1 2)]                 [b (* b b)])        (append a b))

a:     3

reference to undefined identifier: b