X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fdocs%2Fusers_guide%2Fghci.sgml;h=dfcb9555aae649e5ff3b39482b6cd2fc1e9c6a0f;hb=5affd8114e7ba87fa289eb72760a597456aea4cb;hp=54952ecdb3737144081a0272820f414593814c10;hpb=1f35e3ac4ac5b74cdeb30058bc01ab36766b25c8;p=ghc-hetmet.git
diff --git a/ghc/docs/users_guide/ghci.sgml b/ghc/docs/users_guide/ghci.sgml
index 54952ec..dfcb955 100644
--- a/ghc/docs/users_guide/ghci.sgml
+++ b/ghc/docs/users_guide/ghci.sgml
@@ -44,36 +44,36 @@ Prelude>
Commands available from the prompt:
- %lt;stmt> evaluate/run %lt;stmt>
- :add %lt;filename> ... add module(s) to the current target set
- :browse [*]%lt;module> display the names defined by %lt;module>
- :cd %lt;dir> change directory to %lt;dir>
- :def %lt;cmd> %lt;expr> define a command :%lt;cmd>
+ <stmt> evaluate/run <stmt>
+ :add <filename> ... add module(s) to the current target set
+ :browse [*]<module> display the names defined by <module>
+ :cd <dir> change directory to <dir>
+ :def <cmd> <expr> define a command :<cmd>
:help, :? display this list of commands
- :info [%lt;name> ...] display information about the given names
- :load %lt;filename> ... load module(s) and their dependents
- :module [+/-] [*]%lt;mod> ... set the context for expression evaluation
+ :info [<name> ...] display information about the given names
+ :load <filename> ... load module(s) and their dependents
+ :module [+/-] [*]<mod> ... set the context for expression evaluation
:reload reload the current module set
- :set %lt;option> ... set options
- :set args %lt;arg> ... set the arguments returned by System.getArgs
- :set prog %lt;progname> set the value returned by System.getProgName
+ :set <option> ... set options
+ :set args <arg> ... set the arguments returned by System.getArgs
+ :set prog <progname> set the value returned by System.getProgName
:show modules show the currently loaded modules
:show bindings show the current bindings made at the prompt
- :type %lt;expr> show the type of %lt;expr>
- :undef %lt;cmd> undefine user-defined command :%lt;cmd>
- :unset %lt;option> ... unset options
+ :type <expr> show the type of <expr>
+ :undef <cmd> undefine user-defined command :<cmd>
+ :unset <option> ... unset options
:quit exit GHCi
- :!%lt;command> run the shell command %lt;command>
+ :!<command> run the shell command <command>
Options for `:set' and `:unset':
+r revert top-level expressions after each evaluation
+s print timing/memory stats after each evaluation
+t print type after evaluation
- -%lt;flags> most GHC command line flags can also be set here
+ -<flags> most GHC command line flags can also be set here
(eg. -v2, -fglasgow-exts, etc.)
@@ -162,7 +162,7 @@ Ok, modules loaded: Main.
indirectly, by the topmost module, and load them all in dependency
order.
-
+
Modules vs. filenames
modulesand filenames
filenamesof modules
@@ -207,10 +207,6 @@ 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 +637,32 @@ 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 class,
+ GHCi will try to use one of the default types, just as described in the Report.
+
+
@@ -672,26 +694,33 @@ $ ghci Main.hs
Packages
packageswith 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 +731,7 @@ Prelude> :set -package name
But 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 +740,10 @@ Prelude> :set -package name
Extra 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
@@ -1222,22 +1254,6 @@ 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!