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diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml
index 5daa29c..1f20df4 100644
--- a/docs/users_guide/ghci.xml
+++ b/docs/users_guide/ghci.xml
@@ -202,12 +202,12 @@ Ok, modules loaded: Main.
very often, and use the interpreter for the code being actively
developed.
- When loading up source files with :load,
- GHCi looks for any corresponding compiled object files, and will
- use one in preference to interpreting the source if possible. For
- example, suppose we have a 4-module program consisting of modules
- A, B, C, and D. Modules B and C both import D only,
- and A imports both B & C:
+ When loading up source modules with :load,
+ GHCi normally looks for any corresponding compiled object files,
+ and will use one in preference to interpreting the source if
+ possible. For example, suppose we have a 4-module program
+ consisting of modules A, B, C, and D. Modules B and C both import
+ D only, and A imports both B & C:
A
/ \
@@ -298,6 +298,17 @@ Compiling A ( A.hs, interpreted )
Ok, modules loaded: A, B, C, D.
+ The automatic loading of object files can sometimes lead to
+ confusion, because non-exported top-level definitions of a module
+ are only available for use in expressions at the prompt when the
+ module is interpreted (see ). For
+ this reason, if you ask GHCi to load a filename rather than a
+ module name (e.g. :load Main.hs rather than
+ :load Main) then any existing object file will
+ be ignored and the module will be interpreted rather than
+ compiled. Using -fobject-code disables this
+ behaviour (see ).
+
HINT: since GHCi will only use a compiled object file if it
can be sure that the compiled version is up-to-date, a good technique
when working on a large program is to occasionally run
@@ -306,7 +317,6 @@ Ok, modules loaded: A, B, C, D.
interpreter. As you modify code, the changed modules will be
interpreted, but the rest of the project will remain
compiled.
-
@@ -537,10 +547,14 @@ Compiling Main ( Main.hs, interpreted )
scopes from multiple modules, in any mixture of
* and non-* forms. GHCi
combines the scopes from all of these modules to form the scope
- that is in effect at the prompt. For technical reasons, GHCi
- can only support the *-form for modules which
- are interpreted, so compiled modules and package modules can
- only contribute their exports to the current scope.
+ that is in effect at the prompt.
+
+ NOTE: for technical reasons, GHCi can only support the
+ *-form for modules that are interpreted.
+ Compiled modules and package modules can only contribute their
+ exports to the current scope. This is why GHCi will always
+ interpret, not compile, a module if you specify its filename
+ rather than its module name to :load.The scope is manipulated using the
:module command. For example, if the current
@@ -602,12 +616,48 @@ Prelude IO>
+ :module and
+ :load
+
+ It might seem that :module and
+ :load do similar things: you can use both
+ to bring a module into scope. However, there is a clear
+ difference. GHCi is concerned with two sets of modules:
+
+
+
+ The set of modules that are
+ currently loaded. This set is
+ modified
+ by :load, :add
+ and :reload.
+
+
+
+ The set of modules that are currently in
+ scope at the prompt. This set is modified
+ by :module, and it is also set
+ automatically
+ after :load, :add,
+ and :reload.
+
+
+
+ You cannot add a module to the scope if it is not
+ loaded. This is why trying to
+ use :module to load a new module results
+ in the message “module M is not
+ loaded”.
+
+
+ Qualified namesTo make life slightly easier, the GHCi prompt also
behaves as if there is an implicit import
qualified declaration for every module in every
- package, and every module currently loaded into GHCi.
+ package, and every module currently loaded into GHCi. This
+ behaviour can be disabled with the flag .
@@ -845,10 +895,12 @@ def = toEnum 0
GHCi contains a simple imperative-style debugger in which you can
stop a running computation in order to examine the values of
variables. The debugger is integrated into GHCi, and is turned on by
- default: no flags are required to enable the debugging facilities. There
- is one major restriction: breakpoints and single-stepping are only
- available in interpreted modules; compiled code is
- invisible to the debugger.
+ default: no flags are required to enable the debugging
+ facilities. There is one major restriction: breakpoints and
+ single-stepping are only available in interpreted modules;
+ compiled code is invisible to the debuggerNote that packages
+ only contain compiled code, so debugging a package requires
+ finding its source and loading that directly..
The debugger provides the following:
@@ -883,9 +935,12 @@ def = toEnum 0
There is currently no support for obtaining a “stack
- trace”, but the tracing and history features provide a useful
- second-best, which will often be enough to establish the context of an
- error.
+ trace”, but the tracing and history features provide a
+ useful second-best, which will often be enough to establish the
+ context of an error. For instance, it is possible to break
+ automatically when an exception is thrown, even if it is thrown
+ from within compiled code (see ).
Breakpoints and inspecting variables
@@ -2662,6 +2717,22 @@ Prelude> :set -fno-glasgow-exts
:set like this. The changes won't take effect
until the next :load, though.)
+ Once you have a library of GHCi macros, you may want
+ to source them from separate files, or you may want to source
+ your .ghci file into your running GHCi
+ session while debugging it
+
+
+:def source readFile
+
+
+ With this macro defined in your .ghci
+ file, you can use :source file to read GHCi
+ commands from file. You can find (and contribute!-)
+ other suggestions for .ghci files on this Haskell
+ wiki page: GHC/GHCi
+
Two command-line options control whether the
startup files files are read: