X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fghci.xml;h=7c3fed2e8b5b0902db94349d6141dd5d7340e7ca;hb=eccb2d89eb4b34f31e8ea337d5f8673605f71665;hp=0a50bcc554d5eb03c6005b11e03a14b6f7b60fe6;hpb=e192dcbfaf85e299ac49b0e2ba3475fc1d517291;p=ghc-hetmet.git
diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml
index 0a50bcc..7c3fed2 100644
--- a/docs/users_guide/ghci.xml
+++ b/docs/users_guide/ghci.xml
@@ -28,8 +28,11 @@
$ ghci
-GHCi, version 6.8.1: http://www.haskell.org/ghc/ :? for help
+GHCi, version 6.12.1: http://www.haskell.org/ghc/ :? for help
+Loading package ghc-prim ... linking ... done.
+Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
+Loading package ffi-1.0 ... linking ... done.
Prelude>
@@ -55,8 +58,52 @@ Prelude>
GHCi interprets the whole line as an expression to evaluate.
- The expression may not span several lines - as soon as you press
- enter, GHCi will attempt to evaluate it.
+ The expression may not span several lines - as soon as you press enter,
+ GHCi will attempt to evaluate it.
+
+ GHCi also has a multiline mode,
+ :set +m,
+ which is terminated by an empty line:
+
+
+Prelude> :set +m
+Prelude> let x = 42 in x / 9
+Prelude|
+4.666666666666667
+Prelude>
+
+
+ In Haskell, a let expression is followed
+ by in. However, in GHCi, since the expression
+ can also be interpreted in the IO monad,
+ a let binding with no accompanying
+ in statement can be signalled by an empty line,
+ as in the above example.
+
+ Multiline mode is useful when entering monadic
+ do statements:
+
+
+Control.Monad.State> flip evalStateT 0 $ do
+Control.Monad.State| i <- get
+Control.Monad.State| lift $ do
+Control.Monad.State| putStrLn "Hello World!"
+Control.Monad.State| print i
+Control.Monad.State|
+"Hello World!"
+0
+Control.Monad.State>
+
+
+ During a multiline interaction, the user can interrupt and
+ return to the top-level prompt.
+
+
+Prelude> do
+Prelude| putStrLn "Hello, World!"
+Prelude| ^C
+Prelude>
+
@@ -586,10 +633,12 @@ hello
Prelude IO>
- (Note: you can use import M as an
- alternative to :module +M, and
+ (Note: you can use conventional
+ haskell import syntax as
+ well, but this does not support
+ * forms).
:module can also be shortened to
- :m). The full syntax of the
+ :m. The full syntax of the
:module command is:
@@ -814,16 +863,16 @@ it <- e
ghci> reverse []
What should GHCi do? Strictly speaking, the program is ambiguous. show (reverse [])
- (which is what GHCi computes here) has type Show a => a and how that displays depends
+ (which is what GHCi computes here) has type Show a => String and how that displays depends
on the type a. For example:
- ghci> (reverse []) :: String
+ ghci> reverse ([] :: String)
""
- ghci> (reverse []) :: [Int]
+ ghci> reverse ([] :: [Int])
[]
However, it is tiresome for the user to have to specify the type, so GHCi extends Haskell's type-defaulting
- rules (Section 4.3.4 of the Haskell 98 Report (Revised)) as follows. The
+ rules (Section 4.3.4 of the Haskell 2010 Report) as follows. The
standard rules take each group of constraints (C1 a, C2 a, ..., Cn
a) for each type variable a, and defaults the
type variable if
@@ -1938,8 +1987,7 @@ maybe :: b -> (a -> b) -> Maybe a -> b
used, respectively. Tags for all the functions, constructors and
types in the currently loaded modules are created. All modules must
be interpreted for these commands to work.
- See also .
-
+
@@ -2341,6 +2389,19 @@ bar
+ :script n
+ filename
+ :script
+
+
+ Executes the lines of a file as a series of GHCi commands. This command
+ is compatible with multiline statements as set by :set +m
+
+
+
+
+
+
:set option...
:set
@@ -2623,6 +2684,18 @@ bar
+ +m
+ +m
+
+
+ Enable parsing of multiline commands. A multiline command
+ is prompted for when the current input line contains open layout
+ contexts.
+
+
+
+
+
+r
+r
CAFsin GHCi
@@ -2934,7 +3007,6 @@ Prelude> :set -fno-glasgow-exts