X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=docs%2Fusers_guide%2Fghci.xml;h=3ba2012eee34a086f7cd4ac1cb7fa227c7f6c1a5;hb=0093a2827f6b4007c4fcb298a559c9b7dd17aec1;hp=82ee33054d6bdbeda1f1b04cc26730a7abfac83f;hpb=8fcfc8d6e42ea5bf49422024bc71d3728ee97db9;p=ghc-hetmet.git diff --git a/docs/users_guide/ghci.xml b/docs/users_guide/ghci.xml index 82ee330..3ba2012 100644 --- a/docs/users_guide/ghci.xml +++ b/docs/users_guide/ghci.xml @@ -393,9 +393,9 @@ Prelude> Show - The automatic printing of binding results can be supressed with + The automatic printing of binding results can be suppressed with (this does not - supress printing the result of non-binding statements). + suppress printing the result of non-binding statements). . You might want to do this to prevent the result of binding statements from being fully evaluated by the act of printing @@ -929,6 +929,7 @@ right :: [a] left: +[qsort.hs:2:15-46] *Main> :set -fprint-evld-with-show [qsort.hs:2:15-46] *Main> :print left left = (_t1::[a]) @@ -948,6 +949,13 @@ left = (_t1::[a]) underscore, in this case _t1. + The flag -fprint-evld-with-show instructs + :print to reuse + available Show instances when possible. This happens + only when the contents of the variable being inspected + are completely evaluated. + + If we aren't concerned about preserving the evaluatedness of a variable, we can use :force instead of :print. The :force command @@ -1017,6 +1025,7 @@ right :: [a] The execution continued at the point it previously stopped, and has now stopped at the breakpoint for a second time. + Setting breakpoints @@ -1109,8 +1118,10 @@ right :: [a] bug. GHCi offers two variants of stepping. Use :step to enable all the breakpoints in the program, and execute until the next breakpoint is - reached. Use :stepover to step over function - applications, which of course are executed all the same. + reached. Use :steplocal to limit the set + of enabled breakpoints to those in the current top level function. + Similarly, use :stepmodule to single step only on + breakpoints contained in the current module. For example: @@ -1122,51 +1133,12 @@ _result :: IO () The command :step expr begins the evaluation of expr in single-stepping mode. If - expr is ommitted, then it single-steps from + expr is omitted, then it single-steps from the current breakpoint. :stepover works similarly. - - In the current version of the debugger, :stepover - is limited to work locally in the lexical sense, that is in the context - of the current expression body. - When you run to the end of the expression, :stepover - stops working and switches to behave like regular :step. - This means - that it will fail to step over the last function application. As a result, - currently :stepover works great for monadic code, but - interacts less perfectly with pure code. For example, if stopped at the - line 2, on the entire expression - qsort left ++ [a] ++ qsort right: - -... [qsort2.hs:2:15-46] *Main> :step -Stopped at qsort2.hs:2:15-46 - -... [qsort2.hs:2:15-46] *Main> :list -2 qsort (a:as) = qsort left ++ [a] ++ qsort right - - - The first :stepover will step over the first - qsort recursive call, as expected. The second one - will step over the evaluation of [a], again as - expected. However, the third one has lexically run out - of the current expression, and will behave like regular - :step, performing one step of lazy evaluation and - stopping at the next breakpoint. In this case it is indeed the second - recursive application of qsort. - -[qsort2.hs:2:36-46] *Main> :stepover -Warning: no more breakpoints in this function body, switching to :step -Stopped at qsort2.hs:(1,0)-(3,55) - -[qsort2.hs:2:36-46] *Main> :list -_result :: [a] -1 qsort [] = [] -2 qsort (a:as) = qsort left ++ [a] ++ qsort right -3 where (left,right) = (filter (<=a) as, filter (>a) as) - + The :list command is particularly useful when - single-stepping, to see where you currently are, as just shown - in the above example. + single-stepping, to see where you currently are: [qsort.hs:5:7-47] *Main> :list @@ -1372,9 +1344,13 @@ a :: a :trace and :history to establish the context. However, head is in a library and we can't set a breakpoint on it directly. For this reason, GHCi - provides the flag -fbreak-on-exception which causes - the evaluator to stop when an exception is thrown, just as it does when - a breakpoint is hit. This is only really useful in conjunction with + provides the flags -fbreak-on-exception which causes + the evaluator to stop when an exception is thrown, and + -fbreak-on-error, which works similarly but stops only on + uncaught exceptions. When stopping at an exception, GHCi will act + just as it does when a breakpoint is hit, with the deviation that it + will not show you any source code location. Due to this, these + commands are only really useful in conjunction with :trace, in order to log the steps leading up to the exception. For example: @@ -1528,10 +1504,6 @@ Just 20 CAF (e.g. main), stop at a breakpoint, and ask for the value of the CAF at the prompt again. - :stepover only works lexically locally, in the - body of the current expression. As a result, it can be rather impredictable - when used in pure functional code, as opposed to monadic code. - Implicit parameters (see ) are only available at the scope of a breakpoint if there is an explicit type signature. @@ -1708,17 +1680,20 @@ $ ghci -lm - :browse *module ... + :browse *module ... :browse Displays the identifiers defined by the module module, which must be either - loaded into GHCi or be a member of a package. If the - * symbol is placed before the module - name, then all the identifiers defined - in module are shown; otherwise - the list is limited to the exports of + loaded into GHCi or be a member of a package. If + module is omitted, the most + recently-loaded module is used. + + If the * symbol is placed before + the module name, then all the + identifiers in scope in module are + shown; otherwise the list is limited to the exports of module. The *-form is only available for modules which are interpreted; for compiled modules (including @@ -1785,7 +1760,7 @@ $ ghci -lm Generates a “tags” file for Vi-style editors (:ctags) or Emacs-style editors (:etags). If - no filename is specified, the defaulit tags or + no filename is specified, the default tags or TAGS is used, respectively. Tags for all the functions, constructors and types in the currently loaded modules are created. All modules must