4 Console User Interface HPC-GAP has a multi-threaded user interface to assist with the development and debugging of concurrent programs. This user interface is enabled by default; to disable it, and use the single-threaded interface, GAP has to be started with the -S option. 4.1 Console UI commands The console user interface provides the user with the option to control threads by commands prefixed with an exclamation mark ("!"). Those commands are listed below. For ease of use, users only need to type as many letters of each commands so that it can be unambiguously selected. Thus, the shell will recognize !l as an abbreviation for !list. 4.1-1 !shell [name] Starts a new shell thread and switches to it. Optionally, a name for the thread can be provided.  Example  gap> !shell --- Switching to thread 4 [4] gap>  4.1-2 !fork [name] Starts a new background shell thread. Optionally, a name for the thread can be provided.  Example  gap> !fork --- Created new thread 5  4.1-3 !list List all current threads that are interacting with the user. This does not list threads created with CreateThread() that have not entered a break loop.  Example  gap> !list --- Thread 0 [0] --- Thread 4 [4] --- Thread 5 [5] (pending output)  4.1-4 !kill id Terminates the specified thread. 4.1-5 !break id Makes the specified thread enter a break loop. 4.1-6 !name [id] name Give the thread with the numerical identifier or name id the name name.  Example  gap> !name 5 test gap> !list --- Thread 0 [0] --- Thread 4 [4] --- Thread test [5] (pending output)  4.1-7 !info id Provide information about the thread with the numerical identifier or name id. Not yet implemented. 4.1-8 !hide [id|*] Hide output from the thread with the numerical identifier or name id when it is not the foreground thread. If no thread is specified, make this the default behavior for future threads. 4.1-9 !watch [id|*] Show output from the thread with the numerical identifier or name id even when it is not the foreground thread. If no thread is specified, make this the default behavior for future threads. 4.1-10 !keep num Keep num lines of output from each thread. 4.1-11 !prompt (id|*) string Set the prompt for the specified thread (or for all newly created threads if * was specified) to be string. If the string contains the pattern id, it is replaced with the numerical id of the thread; if it contains the pattern name, it is replaced with the name of the thread; if the thread has no name, the numerical id is displayed instead. 4.1-12 !prefix (id|*) string Prefix the output from the specified thread (or for all newly created threads if * was specified) wiht string. The same substitution rules as for the !prompt command apply. 4.1-13 !select id Make the specified thread the foreground thread.  Example  gap> !select 4 gap> !select 4 --- Switching to thread 4 [4] gap>  4.1-14 !next Make the next thread in numerical order the foreground thread. 4.1-15 !previous Make the previous thread in numerical order the foreground thread. 4.1-16 !replay num [id] Display the last num lines of output of the specified thread. If no thread was specified, display the last num lines of the current foreground thread. 4.1-17 !id !id is a shortcut for !select id. 4.1-18 !source file Read commands from file file. 4.1-19 !alias shortcut expansion Create an alias. After defining the alias, !shortcut 'rest of line' will be replaced with !expansion 'rest of line'. 4.1-20 !unalias shortcut Removes the specified alias. 4.1-21 !eval expr Evaluates expr as a command. 4.1-22 !run function string Calls the function with name function, passing it the single argument string as a GAP string. 4.2 GAP functions to access the Shell UI There are several functions to access the basic functionality of the shell user interface. Other than TextUIRegisterCommand (4.2-1), they can only be called from within a registered command. Threads can be specified either by their numerical identifier or by their name (as a string). The empty string can be used to specify the current foreground thread. 4.2-1 TextUIRegisterCommand TextUIRegisterCommand( name, func )  function Registers the command !name with the shell UI. It will call with the rest of the command line passed as a string argument when typed. 4.2-2 TextUIForegroundThread TextUIForegroundThread( )  function Returns the numerical identifier of the current foreground thread. 4.2-3 TextUIForegroundThreadName TextUIForegroundThreadName( )  function Returns the name of the current foreground thread or fail if the current foreground thread has no name. 4.2-4 TextUISelectThread TextUISelectThread( id )  function Makes id the current foreground thread. Returns true or false to indicate success. 4.2-5 TextUIOutputHistory TextUIOutputHistory( id, count )  function Returns the last count lines of the thread specified by id (which can be a numerical identifier or a name). Returns fail if there is no such thread. 4.2-6 TextUISetOutputHistoryLength TextUISetOutputHistoryLength( length )  function By default, retain length lines of output history from each thread. 4.2-7 TextUINewSession TextUINewSession( foreground, name )  function Creates a new shell thread. Here, foreground is a boolean variable specifying whether it should be made the new foreground thread and name is the name of the thread. The empty string can be used to leave the thread without a name. 4.2-8 TextUIRunCommand TextUIRunCommand( command )  function Run the command denoted by command as though a user had typed it. The command must not contain a newline character. 4.2-9 TextUIWritePrompt TextUIWritePrompt( )  function Display a prompt for the current thread.