====== Language plugins ======

===== Framework =====

Language plugins read and write a particular simulation language, and set up related commands.  They determine the syntax used by gnucap.

This refers to SIMULATION languages, like "spice", "spectre" or "verilog", not NATURAL languages.

Language plugins need to #include the file: ''gnucap/lang_base.h''.  Others may be needed in some cases.

The base class ''LANGUAGE'' is defined in ''gnucap/u_lang.h'' which is included by ''gnucap/lang_base.h''.

The "parse" and "print" functions go together.  For every "parse" there must be a "print" that regenerates a string suitable for input to "parse" that is equivalent to the original.

As a generalization, to read a file the function ''parse_top_item'' is called in a loop:

<code>
  for (;;) {
    OPT::language->parse_top_item(file, Scope);
  }
</code>

The loop exits when an exception is thrown, most likely ''Exception_End_Of_Input''.

This function must be provided by the language plugin.  A set of other functions must also be provided, as in this example:

As with all plugins, declare one static object of this new type, and INSTALL it in the DISPATCHER.

In addition to this, you will probably need to supply a few commands to recognize keywords at top level.

Details are described in the following "Implementation" section.


===== Implementation =====

  * [[.:languages:Top level]]
  * [[.:languages:lang_base.h]]
  * [[.:languages:Simple query functions]]
  * [[.:languages:parse_top_item]]
  * [[.:languages:find_type_in_string]]
  * [[.:languages:comment]]
  * [[.:languages:command]]
  * [[.:languages:instance|instance, paramset]]
  * [[.:languages:module]]
  * [[.:languages:attributes]]