diff options
Diffstat (limited to 'racket.html.markdown')
| -rw-r--r-- | racket.html.markdown | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/racket.html.markdown b/racket.html.markdown index bf94db90..d43ac5e2 100644 --- a/racket.html.markdown +++ b/racket.html.markdown @@ -441,7 +441,7 @@ vec ; => #(1 2 3 4) (set! i (add1 i)))) ;; Macros are hygienic, you cannot clobber existing variables! -(define-syntax-rule (swap x y) +(define-syntax-rule (swap! x y) ; -! is idomatic for mutation (let ([tmp x]) (set! x y) (set! y tmp))) @@ -449,7 +449,7 @@ vec ; => #(1 2 3 4) (define tmp 1) (define a 2) (define b 3) -(swap a b) +(swap! a b) (printf "tmp = ~a; a = ~a; b = ~a\n" tmp a b) ; tmp is unaffected ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; |