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Diffstat (limited to 'dev-haskell/readargs/metadata.xml')
| -rw-r--r-- | dev-haskell/readargs/metadata.xml | 71 |
1 files changed, 71 insertions, 0 deletions
diff --git a/dev-haskell/readargs/metadata.xml b/dev-haskell/readargs/metadata.xml new file mode 100644 index 000000000000..240a652b0a68 --- /dev/null +++ b/dev-haskell/readargs/metadata.xml @@ -0,0 +1,71 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd"> +<pkgmetadata> + <herd>haskell</herd> + <longdescription> + ReadArgs provides the @readArgs@ IO action, which lets you tell the compiler + to parse the command line arguments to fit the type signature you give. + + For example @(a :: Int, b :: String, c :: Float) <- readArgs@ would + parse the first runtime argument as an @Int@, the second as a @String@ (no + quotes required) and the third as a @Float@. + + If the runtime arguments are incompatible with the type signature, + then a simple usage statement is given of the types needed. + + Continuing the previous example, if it was used in a + program named @Example@, the error message for the above + action would be: + + @ + usage: Example Int String Float + @ + + Any type that has both @Typeable@ and @Read@ instances + can be used. @Char@, @String@, and @Text@ are handled specially so that + command line arguments for both do not require quotes (as their + @Read@ instances do). A special instance is provided for @FilePath@ so + that no constructor or quotes are required. + + @readArgs@ also supports optional arguments and variadic arguments. + Optional arguments are specified using @Maybe@, and variadic arguments + using a list. @(a :: Int, b :: Maybe String, c :: [Float]) <- readArgs@ + would successfully parse any of the following sets of command line arguments: + + @ + Example 1 + Example 1 2 3 4 + Example 1 foo + Example 1 foo 2 3 4 + @ + + But not + + @ + Example + Example foo + Example 1.0 + @ + + Usage statements for optional and variadic arguments use command-line + parlance: + + @ + usage: Example Int [String] [Float..] + @ + + Note that both optional and variadic parsers are greedy by default + (so @Example 1 2 3 4@ was parsed as @(1, "2", [3.0,4.0])@. They + may both be made non-greedy through use of the @NonGreedy@ constructor: + + @ + ( a :: Int + , NonGreedy b :: NonGreedy Maybe String + , NonGreedy c :: NonGreedy [] Float + ) <- readArgs + @ + </longdescription> + <upstream> + <remote-id type="github">rampion/ReadArgs</remote-id> + </upstream> +</pkgmetadata> |