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Diffstat (limited to 'examples/do.scm')
-rw-r--r-- | examples/do.scm | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/examples/do.scm b/examples/do.scm new file mode 100644 index 0000000..d758177 --- /dev/null +++ b/examples/do.scm @@ -0,0 +1,41 @@ +(add-to-load-path (dirname (current-filename))) + +(use-modules (control monad) + (data monoid) + (data optional) + (data writer)) + +;;; Optional Monad, and do notation + +(do x <- (just 10) + x) ; => 10 + +(do let y = (just 10) + x <- y + (+ x 5)) ; => 15 + +(do x <- (nothing) + (+ x 5)) ; => [Nothing] + +(do x <- (just 10) + y <- (just 20) + (+ x y)) ; => 30 + +(do (just 10) + (nothing) + (just 20)) ; => [Nothing] + +;;; Writer Monad, and do notation + +;; Int -> Writer Int String +(define (log-number n) + (writer n (format #f "Got nuber: ~a" n))) + +(do a <- (log-number 3) + b <- (log-number 5) + (writer (* a b) "")) +;; => [Writer 15, "Got nuber: 3Got nuber: 5"] + +(do (log-number 3) + (log-number 5)) +;; => [Writer 5, "Got nuber: 3Got nuber: 5"] |