X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fghci.xml;h=d9295484c85e2f84ddf5ea1550b7604f6898e7a4;hb=aedb94f5f220b5e442b23ecc445fd38c8d9b6ba0;hp=5daa29c9a12eb6faf5d9c6db5834e449bd9c5baa;hpb=878ce92d0559e10a083b6983f2d23380086026d8;p=ghc-hetmet.git diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml index 5daa29c..d929548 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 +298,34 @@ 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, you might sometimes want to force GHCi to load a + module using the interpreter. This can be done by prefixing + a * to the module name or filename when + using :load, for example + + +Prelude> :load *A +Compiling A ( A.hs, interpreted ) +*A> + + +When the * is used, GHCi ignores any + pre-compiled object code and interprets the module. If you have + already loaded a number of modules as object code and decide that + you wanted to interpret one of them, instead of re-loading the whole + set you can use :add *M to specify that you want + M to be interpreted (note that this might cause + other modules to be interpreted too, because compiled modules cannot + depend on interpreted ones). + +To always compile everything to object code and never use the + interpreter, use the -fobject-code option (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 +334,6 @@ 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 +564,14 @@ 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. To ensure that GHCi loads the + interpreted version of a module, add the * + when loading the module, e.g. :load *M. The scope is manipulated using the :module command. For example, if the current @@ -602,12 +633,48 @@ Prelude IO> + <literal>:module</literal> and + <literal>:load</literal> + + 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 names To 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 +912,12 @@ 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 +952,12 @@ 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 @@ -1422,7 +1494,7 @@ a :: a *Main> :set -fbreak-on-exception *Main> :trace qsort ("abc" ++ undefined) -"Stopped at <exception thrown> +“Stopped at <exception thrown> _exception :: e [<exception thrown>] *Main> :hist -1 : qsort.hs:3:24-38 @@ -1707,13 +1779,16 @@ $ ghci -lm - :add module ... + :add *module ... :add Add module(s) to the current target set, and perform a - reload. + reload. Normally pre-compiled code for the module will be + loaded if available, or otherwise the module will be + compiled to byte-code. Using the * + prefix forces the module to be loaded as byte-code. @@ -2084,7 +2159,7 @@ Prelude> :. cmds.ghci - :load module ... + :load *module ... :load @@ -2101,6 +2176,11 @@ Prelude> :. cmds.ghci to unload all the currently loaded modules and bindings. + Normally pre-compiled code for a module will be loaded + if available, or otherwise the module will be compiled to + byte-code. Using the * prefix forces a + module to be loaded as byte-code. + After a :load command, the current context is set to: @@ -2306,7 +2386,9 @@ bar Inside prompt, the sequence %s is replaced by the names of the modules currently in scope, and %% is - replaced by %. + replaced by %. If prompt + starts with " then it is parsed as a Haskell String; + otherwise it is treated as a literal string. @@ -2662,6 +2744,22 @@ 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: