X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fghci.xml;h=c2bceeae4c06d30690b4012b2c10885949b576f1;hb=f61baf76c9fa20aa972938384887bcb52151e76f;hp=299b1e5bb28477e8a59d4e3317b008ecacb1d3d3;hpb=087fc5a777f18ef6fa488d168cdf18ef8a22f374;p=ghc-hetmet.git diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml index 299b1e5..c2bceea 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> @@ -302,12 +305,29 @@ Ok, modules loaded: A, B, C, D. 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 ). + 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 @@ -552,9 +572,9 @@ Compiling Main ( Main.hs, interpreted ) 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. + 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 @@ -569,10 +589,12 @@ 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: @@ -650,13 +672,14 @@ Prelude IO> 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 . @@ -796,12 +819,12 @@ 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 @@ -1476,7 +1499,7 @@ 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 @@ -1761,13 +1784,16 @@ $ 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. @@ -2138,7 +2164,7 @@ Prelude> :. cmds.ghci - :load module ... + :load *module ... :load @@ -2155,6 +2181,11 @@ 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: @@ -2305,6 +2336,16 @@ bar + :run + :run + + + See :main. + + + + + :set option... :set @@ -2360,7 +2401,9 @@ 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. @@ -2880,6 +2923,13 @@ Prelude> :set -fno-glasgow-exts because this is normally what you want in an interpreter: output appears as it is generated. + + If you want line-buffered behaviour, as in GHC, you can + start your program thus: + + main = do { hSetBuffering stdout LineBuffering; ... } + + @@ -2889,7 +2939,6 @@ Prelude> :set -fno-glasgow-exts