Difference between revisions of "Cecil"

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(in French, English words are in italics. In English, they don't need to ;-))
 
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[[Category:Book]]
 
[[Category:Book]]
   
Cecil is a mecanism that permits to call Eiffel code from C. In this way, it is the opposite of [[externals]].
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Cecil is a mechanism that permits to call Eiffel code from C. In this way, it is the opposite of [[externals]].
   
 
In order to call Eiffel from C, you must use the flag <TT>-cecil&nbsp;&lt;cecil_file&gt;</TT> with [[compile]] or [[compile_to_c]]. The file <TT>&lt;cecil_file&gt;</TT> must give the list of [[Glossary#Feature|features]] that you want to call from C. The stub routines are automatically generated by SmartEiffel.
 
In order to call Eiffel from C, you must use the flag <TT>-cecil&nbsp;&lt;cecil_file&gt;</TT> with [[compile]] or [[compile_to_c]]. The file <TT>&lt;cecil_file&gt;</TT> must give the list of [[Glossary#Feature|features]] that you want to call from C. The stub routines are automatically generated by SmartEiffel.
   
When the flag <TT>-cecil</TT> is used, [[compile_to_c]] also produces one more C header file, which contains all stubs routines prototypes.
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When the flag <TT>-cecil</TT> is used, [[compile_to_c]] also produces one more C header file, which contains all stub routine prototypes.
   
Your <TT>&lt;cecil_file&gt;</TT> file must contain at least two lines. The first line is the name of the C header file to produce (a <TT>.h</TT> file). The others lines have the following structure:
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Your <TT>&lt;cecil_file&gt;</TT> file must contain at least two lines. The first line is the name of the C header file to produce (a <TT>.h</TT> file). The other lines have the following structure:
   
 
&lt;c_name&gt; &lt;eiffel_type&gt; &lt;feature_name&gt;
 
&lt;c_name&gt; &lt;eiffel_type&gt; &lt;feature_name&gt;
   
The <TT>&lt;c_name&gt;</TT> is the name of the C stub routine that wraps the Eiffel call. The couple <TT>&lt;eiffel_type&gt; &lt;feature_name&gt;</TT> give the complete name of the Eiffel [[Glossary#Feature|feature]] to call.
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The <TT>&lt;c_name&gt;</TT> is the name of the C stub routine that wraps the Eiffel call. The couple <TT>&lt;eiffel_type&gt; &lt;feature_name&gt;</TT> gives the complete name of the Eiffel [[Glossary#Feature|feature]] to call.
   
 
You can also put Eiffel-style comments.
 
You can also put Eiffel-style comments.
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Nota bene:
 
Nota bene:
* since attributes are [[Glossary#Feature|features]], it is of course possible to access them with this mecanism.
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* since attributes are [[Glossary#Feature|features]], it is of course possible to access them with this mechanism.
 
* The [[Glossary#LateBinding|late binding]] is also taken in account. In the above example, a call to <TT>X_f()</TT> in C is equivalent to the call <TT>x.f</TT> in Eiffel, with <TT>x</TT> of type <TT>X</TT> ''or a descendant of <TT>X</TT>''.
 
* The [[Glossary#LateBinding|late binding]] is also taken in account. In the above example, a call to <TT>X_f()</TT> in C is equivalent to the call <TT>x.f</TT> in Eiffel, with <TT>x</TT> of type <TT>X</TT> ''or a descendant of <TT>X</TT>''.
   
Here is another example of a Cecil file (other can be found in the tutorial <TT>SmartEiffel/tutorial/cecil</TT>):
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Here is another example of a Cecil file (more can be found in the tutorial <TT>SmartEiffel/tutorial/cecil</TT>):
 
-- The name of the include C file:
 
-- The name of the include C file:
 
eiffel.h
 
eiffel.h

Revision as of 14:03, 16 July 2005


Cecil is a mechanism that permits to call Eiffel code from C. In this way, it is the opposite of externals.

In order to call Eiffel from C, you must use the flag -cecil <cecil_file> with compile or compile_to_c. The file <cecil_file> must give the list of features that you want to call from C. The stub routines are automatically generated by SmartEiffel.

When the flag -cecil is used, compile_to_c also produces one more C header file, which contains all stub routine prototypes.

Your <cecil_file> file must contain at least two lines. The first line is the name of the C header file to produce (a .h file). The other lines have the following structure:

<c_name>    <eiffel_type>    <feature_name>

The <c_name> is the name of the C stub routine that wraps the Eiffel call. The couple <eiffel_type> <feature_name> gives the complete name of the Eiffel feature to call.

You can also put Eiffel-style comments.

For example:

-- features from STRING :
StringIsEmpty  STRING         empty
StringItem     STRING         item
StringGT       STRING         infix ">"
-- features from ARRAY[INTEGER] :
IntArrayCount  ARRAY[INTEGER] count
IntArrayItem   ARRAY[INTEGER] item
-- features from X :
X_f            X              f

Please note that the <type_eiffel> must be a live type. For example, if the <eiffel_type> is ARRAY[INTEGER], your Eiffel program must at least create one instance of type ARRAY[INTEGER].

The name of the feature to call, <feature_name>, can be a prefix or infix name. The syntax is the same as the one used in the Eiffel source code.

Nota bene:

  • since attributes are features, it is of course possible to access them with this mechanism.
  • The late binding is also taken in account. In the above example, a call to X_f() in C is equivalent to the call x.f in Eiffel, with x of type X or a descendant of X.

Here is another example of a Cecil file (more can be found in the tutorial SmartEiffel/tutorial/cecil):

-- The name of the include C file:
eiffel.h
-- The features you want to call from C:
array_of_animal_item  ARRAY[ANIMAL] item
array_of_animal_lower ARRAY[ANIMAL] lower
array_of_animal_upper ARRAY[ANIMAL] upper
cry                   ANIMAL        cry
string_to_external    STRING        to_external