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<title>Program code representations</title>
<h1>5 <a name="s5"> Program code representations </h1>
<p> <a href="usrguide.html#toc5"> Contents of this section</a></p>
<p>Thus far we have used and studied only one form of existence of our
programs, namely the native Tela source code (t-files and command
line). Both internally and externally, programs exist in other forms
too. Here is a complete list of all code representations in Tela:</p>
<p>
<pre>
- t-code (the native Tela code)
- "TreeCode" (internal representation for t-code)
- "FlatCode" (another internal representation for t-code)
- C-tela code (code similar to C++)
- Compiled object code (machine language)
</pre>
</p>
<p>When a program is <b>source</b>'d (
source </a>
) in or when a
command line is typed, a lexical analyzer first breaks it in tokens,
that is, keywords, separators, numbers, identifiers etc. The output of
the lexical analyzer is a stream of tokens without hierarchical
structure. A parser continues to produce a treelike representation,
the TreeCode. The TreeCode is no longer a stream but has structure in
it. TreeCode is immediately translated into FlatCode, which is a
sequence of virtual machine instructions that the Tela kernel can
understand, and it is reminiscent to assembly language. You can see
both TreeCode and FlatCode representations of your input by setting
the VerboseMode on:</p>
<p>
<blockquote><code>
<pre>
>VerboseMode(on)
0
>1 + 2.3*pi
BLOCK[SET[PLUS[1,TIMES[2.3,pi]]],NOP]
Source file: "stdin"
no input args, no output args, no locals, stack frame size 1.
Maximum number of operands is 3.
0 MUL $0,2.3,pi
4 INC $0
6 PRI $0
8.22566
</pre>
</code></blockquote>
</p>
<p>Alternatively, you can invoke Tela with the --verbose or -v flag. The
FlatCode of any <em>source</em>'d (
source </a>source </a>
) function can be
seen by using <em>disasm</em> (
source </a>source </a>disasm </a>
):</p>
<p>
<pre>
>disasm(mean)
Disassembly of 'mean', Source file: "std.t"
1 input arg, 1 output arg, no locals, stack frame size 4.
Maximum number of operands is 4.
0 CALL sum,1,$3,$1
5 CALL length,1,$0,$1
10 DIV $2,$3,$0
</pre>
</p>
<p>The definition of <em>mean</em> is</p>
<p>
<pre>
function y = mean(x)
// mean(x) computes the arithmetic mean of a numeric array x.
{
y=sum(x)/length(x)
};
</pre>
</p>
<p>and you can easily guess what each of the FlatCode instructions do.</p>
<p>C-tela code is another way to write new functions for Tela. Many Tela
builtin functions are written in C-tela; those which are not are
either in native t-code or are so-called intrinsic functions (meaning
that they generate virtual machine instructions directly like macros).
C-tela code can be compiled into object files using the program
<b>telakka</b> (
source </a>source </a>disasm </a>telakka </a>
). The object files can
be either statically or dynamically linked with the rest of the Tela
kernel.</p>
<p>There exists a standard function <em>t2ct</em> (
source </a>source </a>disasm </a>telakka </a>t2ct </a>
) to translate t-code into C-tela code. The conversion is
made possible by the fact each FlatCode instruction can be made to
correspond simple C-tela codings. As of this writing, however, the
Tela compiling scheme is still somewhat incomplete and under
development. When it is fully functional, you can go all the way from
t-code down to object code automatically.</p>
<p></p>
<p><a href="usrguide-6.html"> Next </a> Chapter, <a href="usrguide-4.html"> Previous </a> Chapter</p><p>Table of contents of <a href="usrguide.html#toc5">this chapter</a>,
General <a href="usrguide.html#toc">table of contents</a></p>
<p><a href="usrguide.html"> Top </a> of the document,
<a href="#0"> Beginning of this Chapter</a></p>
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