diff options
| author | Joey Hess <id@joeyh.name> | 2014-12-01 11:53:40 -0400 |
|---|---|---|
| committer | Joey Hess <id@joeyh.name> | 2014-12-01 11:53:40 -0400 |
| commit | cd8c6114229a5f725bd1818f1fc2d0538c40f486 (patch) | |
| tree | 8b2bab91040caffb3cabee8f5499f9132b376806 | |
| parent | b66c52676142fcfcba84da7852d62d69b8361826 (diff) | |
add question (taken from email) and answer
| -rw-r--r-- | doc/forum/property_combinator_ordering.mdwn | 8 | ||||
| -rw-r--r-- | doc/forum/property_combinator_ordering/comment_1_0ea2186b5cfa7eadaf38ac2e97fc4a2c._comment | 31 |
2 files changed, 39 insertions, 0 deletions
diff --git a/doc/forum/property_combinator_ordering.mdwn b/doc/forum/property_combinator_ordering.mdwn new file mode 100644 index 00000000..25549bb4 --- /dev/null +++ b/doc/forum/property_combinator_ordering.mdwn @@ -0,0 +1,8 @@ +when I write + + setDistribution cfg = f `File.hasContent` cfg + `onChange` update + `requires` File.dirExists confDir + +is update called before ensuring the confiDir Exist ? +It seems to me but who knows ? diff --git a/doc/forum/property_combinator_ordering/comment_1_0ea2186b5cfa7eadaf38ac2e97fc4a2c._comment b/doc/forum/property_combinator_ordering/comment_1_0ea2186b5cfa7eadaf38ac2e97fc4a2c._comment new file mode 100644 index 00000000..c41abd90 --- /dev/null +++ b/doc/forum/property_combinator_ordering/comment_1_0ea2186b5cfa7eadaf38ac2e97fc4a2c._comment @@ -0,0 +1,31 @@ +[[!comment format=mdwn + username="joey" + subject="""comment 1""" + date="2014-12-01T15:53:11Z" + content=""" +I think that should behave intuitively, but of course if you're unsure +of this kind of thing, adding parens is a good way to disambiguate the +code. + + (f `File.hasContent` cfg `onChange` update) + `requires` File.dirExists confDir + +Written that way, it's explicit that the parenthesized part runs +together as one action. + +Or, we can do a quick test in ghci: + + joey@darkstar:~/src/propellor/src#joeyconfig>ghci Propellor.hs Propellor/Property.hs + *Propellor> let f1 = property "hasContent" (liftIO (print "f1") >> return MadeChange) + *Propellor> let f2 = property "update" (liftIO (print "f2") >> return MadeChange) + *Propellor> let f3 = property "dirExists" (liftIO (print "f3") >> return MadeChange) + *Propellor> runPropellor (Host "foo" [] mempty) $ ensureProperty $ f1 `onChange` f2 `requires` f3 + "dirExists" + "hasContent" + "update" + MadeChange + +So, yes, it's behaving as it should, first ensuring that the `requires` +property is met, and then running the main property, and since it made a +change, following up by running the `onChange` property. +"""]] |