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<!-- FIXME: I'd like this file to be generated from the actual strings in Hilfe.pmod 
     and all examples autogenerated in a wrapper like the one in testhilfe.pike --> 
<chapter title="Hilfe"> 
 
<p>Hilfe stands for Hubbes Incremental LPC Front End, and is an 
incremental Pike evaluator. As the name hints Hilfe has its roots back 
when Pike was called LPC, but none of the code from that Hilfe 
remains. Hilfe is one of the most useful tools for Pike developers, 
since it enables them to try various Pike constructions and see how 
they work. Even the most experienced Pike programmer can forget how 
the return data structure of a function looks like or if + or | is the 
best way to merge to mappings for a specific purpose. 
</p> 
 
<section title="Basic operations"> 
 
<p>In short hilfe is a command line version of pike, allowing you to 
   do real time evaluation of pike code. Simply write a line of pike 
   code and press return. If you gave hilfe a complete block of code 
   it will be evaluated and the result will be returned. Side effects will 
   also be effective, hence changing a variable will indeed change the 
   variables value. You are of course not limited to basic variable 
   types like integers and strings, or reference data types like 
   mappings and arrays. You can just as well define functions and 
   classes, enabling you to experiment with inherits, operator 
   overloading and other object oriented things. To start hilfe, just 
   execute the pike binary without any arguments.</p> 
 
<example> 
bash$ pike 
Pike v7.3 release 49 running Hilfe v3.5 (Incremental Pike Frontend) 
> int a=5; 
> a+3.3; 
(1) Result: 8.300000 
> (string)(enumerate(32)[*]+65); 
(2) Result: "ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`" 
> string b=(string)(enumerate(32)[*]+65); 
> b/(a+3.3); 
(3) Result: ({ /* 4 elements */ 
                "ABCDEFGH", 
                "IJKLMNOPQ", 
                "RSTUVWXY", 
                "Z[\\]^_`" 
            }) 
> 
</example> 
 
<p>A history of the 512 last entered lines is kept in Hilfe. You can 
browse this list with your arrow keys up/down. When you exit Hilfe 
your history will be saved in .hilfe_history in the directory set 
in environment variable $HOME or $USERPROFILE. Next time hilfe is 
started the history is imported.</p> 
 
<p>A history of the last returned results is kept and can be accessed 
from your hilfe expressions with the variable <expr>__</expr>. You can 
either "address" your results with absolute addresses, e.g. 
<expr>__[2]</expr> to get the second result ever, or with relative 
addresses, e.g. <expr>__[-1]</expr> to get the last result. The last 
result is also available in the variable <expr>_</expr>, thus 
<expr>_==__[-1]</expr> is true. The magic <expr>_</expr> and 
<expr>__</expr> variable can be shadowed with local definitions to 
disable them, e.g. by typing <expr>int _;</expr>. The result history 
is ten entries long by default, but it could easily be altered by 
using the <tt>set history</tt> command. Note that some Pike code only 
works when there is at most one object created from a class (e.g. the 
Perl module), which means that the result history must be turned off. 
Otherwise the previous object will remain in the history during the 
next nine results.</p> 
 
<p>You can put a .hilferc file in the directory set in your 
environment variable $HOME or $USERPROFILE. The contents of this file 
will be evaluated in hilfe during each startup. It may contain both 
commands and Pike expressions.</p> 
 
<p>One must however always remember that code entered in Hilfe does 
not always work exactly as if it was written in a stand alone Pike 
program. All variables are kept in a mapping so that their values can 
be view and altered by subsequent code lines. Every expression is 
compiled and evaluated in a wrapper which then returns the return 
value to Pike. Use the <tt>dump wrapper</tt> command after a line has 
been evaluated to see the actual code compiled.</p> 
 
<example> 
> int a=5; 
> a+3.3; 
(1) Result: 8.300000 
> dump wrapper 
Last compiled wrapper: 
001: #pragma unpragma_strict_types 
002: mapping(string:mixed) ___hilfe = ___Hilfe->variables; 
003: # 1 
004: mixed ___HilfeWrapper() { return (([mapping(string:int)]___hilfe)->a)+3.3; ; } 
005: 
> 
</example> 
 
<p>Note that there are a few symbols that you can not define, since 
they are used by Hilfe.</p> 
 
<matrix> 
<r><c><expr>___hilfe</expr></c><c>A mapping containing all defined symbols.</c></r> 
<r><c><expr>___Hilfe</expr></c><c>The Hilfe object.</c></r> 
<r><c><expr>___HilfeWrapper</expr></c><c>A wrapper around the entered expression.</c></r> 
</matrix> 
 
</section> 
 
<section title="Commands"> 
 
<p>In addition to be able to enter Pike expressions, there are also a 
few commands available which controls Hilfe. To avoid having the 
commands shadowed by Pike declarations with the same name, it is also 
possible to add a dot in front of the command.</p> 
 
<example> 
> int help=3; 
Hilfe Warning: Command "help" no longer reachable. Use ".help" instead. 
> help 
>> +2; 
(1) Result: 5 
> 
</example> 
 
<subsection title="Help"> 
 
<p>The help command displays a very short introduction to Pike and 
lists all the available commands with a brief explaination.</p> 
 
<example> 
> help 
 
Pike v7.3 release 49 running Hilfe v3.5 (Incremental Pike Frontend) 
Hilfe is a tool to evaluate Pike code interactively and 
incrementally. Any Pike function, expression or variable declaration 
can be entered at the command line. There are also a few extra 
commands: 
 
 dump       - Dump variables and other info. 
 exit       - Exit Hilfe. 
 help       - Show help text. 
 new        - Clears the Hilfe state. 
 quit       - Exit Hilfe. 
 set        - Change Hilfe settings. 
 start      - Start a subsystem. 
 stop       - Stop a subsystem. 
 .          - Abort current input batch. 
 
Enter "help me more" for further Hilfe help. 
> 
</example> 
 
<p>In addition to this elementary help there are a few extra arguments 
that can be given to help to see other help pages. "<tt>help me 
more</tt>" returns a brief summary of everything in this manual 
chapter. "<tt>help hilfe todo</tt>" shows the items in the bug section 
below. "<tt>help about hilfe</tt>" show the Hilfe CVS id string and 
some other version information. In addition to these three arguments 
it is also possible to type help follow with the name of any other 
command. That will display the documentation for that command.</p> 
 
</subsection> 
 
<subsection title="Exit and Quit"> 
<p>It is possible to end a Hilfe session by entering the command 
<tt>exit</tt> or <tt>quit</tt>. It is also possible to exit by using 
Control+D. Note that no history will be saved if Control+C is used to 
terminate Hilfe.</p> 
</subsection> 
 
<subsection title="."> 
</subsection> 
 
<subsection title="dump"> 
</subsection> 
 
<subsection title="new"> 
</subsection> 
 
<subsection title="set"> 
</subsection> 
 
<subsection title="start and stop"> 
</subsection> 
 
</section> 
 
<section title="Subsystems"> 
 
<subsection title="Backend"> 
</subsection> 
 
<subsection title="Logging"> 
</subsection> 
 
</section> 
 
<section title="Bugs and possible improvements"> 
 
<ul> 
<li>Hilfe can not handle sscanf statements like 
  <expr>int a = sscanf("12", "%d", int b);</expr></li> 
<li>The variable scope is not correctly adjusted for sscanf 
  constructions like <expr>sscanf(x, "%2d%2d", int a, int b);</expr></li> 
<li><expr>int x=x;</expr> does not generate an error when <expr>x</expr> is undefined.</li> 
<li>Hilfe can not handle enums.</li> 
<li>Hilfe can not handle typedefs.</li> 
<li>Hilfe can not handle implicit lambdas.</li> 
<li>Hilfe can not handle unnamed classes.</li> 
<li>Hilfe can not handle named lambdas.</li> 
<li>Hilfe should possibly handle imports better, e.g. overwrite the 
  local variables/constants/functions/programs.</li> 
<li>Filter exit/quit from history. Could be done by adding a 'pop' 
  method to Readline.History and calling it from StdinHilfe's 
  destroy.</li> 
<li>Add some better multiline edit support.</li> 
<li>Tab completion of variable and module names.</li> 
</ul> 
 
</section> 
 
</chapter>