X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fdocs%2Fusers_guide%2Fghci.sgml;h=792f68b68f6505d0b4269af70bf92b9163fa7bb1;hb=dc6afe4242238aa1a7a5d3a150a346d23dd6ea22;hp=0ba4d8da401c1054fdaf7eb2c1248a496b53a61a;hpb=f50c833a105e6c7f44c5c43a364dc4ee1803a198;p=ghc-hetmet.git
diff --git a/ghc/docs/users_guide/ghci.sgml b/ghc/docs/users_guide/ghci.sgml
index 0ba4d8d..792f68b 100644
--- a/ghc/docs/users_guide/ghci.sgml
+++ b/ghc/docs/users_guide/ghci.sgml
@@ -63,6 +63,7 @@ Prelude>
:show bindings show the current bindings made at the prompt
:type <expr> show the type of <expr>
+ :kind <type> show the kind of <type>
:undef <cmd> undefine user-defined command :<cmd>
:unset <option> ... unset options
:quit exit GHCi
@@ -162,7 +163,7 @@ Ok, modules loaded: Main.
indirectly, by the topmost module, and load them all in dependency
order.
-
+ Modules vs. filenamesmodulesand filenamesfilenamesof modules
@@ -196,7 +197,7 @@ Ok, modules loaded: Main.
source files, whereas in standard
batch-compilation mode the option is used to
specify the search path for interface files, see .
+ linkend="search-path">.
One consequence of the way that GHCi follows dependencies
to find modules to load is that every module must have a source
@@ -207,10 +208,6 @@ Ok, modules loaded: Main.
which GHCi can't find a source file, even if there are object
and interface files for the module, you'll get an error
message.
-
- One final note: if you load a module called Main, it must
- contain a main function, just like in
- GHC.
@@ -641,6 +638,33 @@ Wed Mar 14 12:23:13 GMT 2001
of it is lost.
+
+
+ Type defaulting in GHCi
+ Type default
+ Show class
+
+ Consider this GHCi session:
+
+ 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
+ on the type a. For example:
+
+ ghci> (reverse []) :: String
+ ""
+ 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. If the expression yields a set of
+ type constraints that are all from standard classes (Num, Eq etc.),
+ and at least one is either a numeric class or the Show,
+ Eq, or Ord class,
+ GHCi will try to use one of the default types, just as described in the Report.
+
+
@@ -672,26 +696,33 @@ $ ghci Main.hs
Packagespackageswith GHCi
- GHCi can make use of all the packages that come with GHC,
- For example, to start up GHCi with the network
- package loaded:
+ Most packages (see ) are
+ available without needing to specify any extra flags at all:
+ they will be automatically loaded the first time they are
+ needed.
+
+ For non-auto packages, however, you need to request the
+ package be loaded by using the -package flag:
-$ ghci -package network
+$ ghci -package data
___ ___ _
/ _ \ /\ /\/ __(_)
- / /_\// /_/ / / | | GHC Interactive, version 5.04, for Haskell 98.
+ / /_\// /_/ / / | | GHC Interactive, version 5.05, for Haskell 98.
/ /_\\/ __ / /___| | http://www.haskell.org/ghc/
\____/\/ /_/\____/|_| Type :? for help.
Loading package base ... linking ... done.
Loading package haskell98 ... linking ... done.
-Loading package network ... linking ... done.
+Loading package lang ... linking ... done.
+Loading package concurrent ... linking ... done.
+Loading package readline ... linking ... done.
+Loading package unix ... linking ... done.
+Loading package posix ... linking ... done.
+Loading package util ... linking ... done.
+Loading package data ... linking ... done.
Prelude>
-
-
- Note that GHCi will also automatically load any packages
- on which the requested package depends.
+
The following command works to load new packages into a
running GHCi:
@@ -702,7 +733,7 @@ Prelude> :set -package nameBut note that doing this will cause all currently loaded
modules to be unloaded, and you'll be dumped back into the
- Prelude.
+ Prelude.
@@ -711,7 +742,10 @@ Prelude> :set -package nameExtra libraries may be specified on the command line using
the normal -llib
- option. For example, to load the “m” library:
+ option. (The term library here refers to
+ libraries of foreign object code; for using libraries of Haskell
+ source code, see .) For
+ example, to load the “m” library:
$ ghci -lm
@@ -745,6 +779,10 @@ $ ghci -lm
(.o or .obj depending on
your platform) from the command-line. Just add the name the
object file to the command line.
+
+ Ordering of options matters: a library
+ should be mentioned before the libraries it
+ depends on (see ).
@@ -804,6 +842,12 @@ $ ghci -lm
beginning of dir will be replaced
by the contents of the environment variable
HOME.
+
+ NOTE: changing directories causes all currently loaded
+ modules to be unloaded. This is because the search path is
+ usually expressed using relative directories, and changing
+ the search path in the middle of a session is not
+ supported.
@@ -1020,6 +1064,17 @@ Prelude> :def make (\_ -> return ":! ghc ––make Main")
+ :kindtype
+ :kind
+
+ Infers and prints the kind of
+ type. The latter can be an arbitrary
+ type expression, including a partial application of a type constructor,
+ such as Either Int.
+
+
+
+ :undefname:undef
@@ -1222,22 +1277,6 @@ Prelude> :set -fno-glasgow-exts
- GHCi complains about main not being
- in scope when I load a module.
- mainwith GHCi
-
-
- You probably omitted the module
- declaration at the top of the module, which causes the
- module name to default to Main. In
- Haskell, the Main module must define a
- function called main. Admittedly this
- doesn't make a great deal of sense for an interpreter, but
- the rule was kept for compatibility with GHC.
-
-
-
- The interpreter can't load modules with foreign export
declarations!