# [scn_pre.h] STYX-konform preprocessing

## contents

#include "standard.h"
#include "symbols.h"
#include "hmap.h"
#include "scn_base.h"

The STYX system comes up with a macro preprocessing facility -
based on the following macro definition syntax and evaluation process during the lexical analysis:

#include Path | supports modular grammar design The macro will be replaced by the content of source file 'Path' and then rescanned.
#macro Name ( FormalParameter , ... ) = Text #end | supports text replacement Parameter and replacement text are optional. The macro will be collected by the preprocessing module and skipped by the scanner. A macro expression ( Name ActualParameter Delimiter ... ) will be replaced by the previous definition and then rescanned.
' Delimiter | introduces another - the second - character as delimiter for the actual macro parameter. Spaces will be used as default delimiter. To reactive the default behaviour specify ' -. The scanner skips these token.
#undefine Name | revokes a previous definition
#if[n]def Name IfPart #else ElsePart #end | supports conditional parsing Dependant on the existence of macro 'Name' the scanner skips the 'ElsePart' or 'IfPart'. Its possible to introduce environment variables as macros.

You can use this preprocessing facility if your regular grammar defines the above kind of macros in the same way -
apart from token names and keywords. ( see below and styx reference )

Note:

The reentrant version of the preprocessing module expects that the preprocessor ( constructed by the function 'SPP_init_reentrant' ) will be added to the scan stream as value of the context variable 'SPP_premac'.

## Types & Macros

SPP_T | Abstract preprocessing type

Identifier for the ( macro ) token names

    #define SPP_TOK_IDE         0 // Identifier
    #define SPP_TOK_MACDFN      1 // Macro
    #define SPP_TOK_MACSEP      2 // Delimiter
    #define SPP_TOK_MACINC      3 // Include
    #define SPP_TOK_MACCOND     4 // Condition
    #define SPP_TOK_MACDEL      5 // Undefine

Identifier for macro token keywords

    #define SPP_PAT_START       6  // #macro
    #define SPP_PAT_END         7  // #end
    #define SPP_PAT_IFDEF       8  // #ifdef
    #define SPP_PAT_IFNDEF      9  // #ifndef
    #define SPP_PAT_ELSE        10 // #else
    #define SPP_PAT_INC         11 // #include
    #define SPP_PAT_UNDEFINE    12 // #undefine

Identifier for include path and character set

    #define SPP_INC_PATH        13
    #define SPP_INC_CHARSET     14

## Macro Expansion

    void SPP_init(MAP(long,symbol) pPreParMap)

initializes STYX-konform macro preprocessing
'pPreParMap': re-definitions for macro token names,
initial macro token keywords,
include path and characterset

    SPP_T SPP_init_reentrant(MAP(long,symbol) pPreParMap)

reentrant version of SPP_init

    void SPP_addCtxMacro(symbol pMacNam)

adds ( lower case symbol ) 'pMacNam' as pre-defined macro

    void SPP_addCtxMacro_reentrant(SPP_T pPP, symbol pMacNam)

reentrant version of SPP_addCtxMacro

    void SPP_quit(void)

terminates STYX-konform macro preprocessing

    void SPP_quit_reentrant(SPP_T pPP)

reentrant version of SPP_quit

    int SPP_premac
        (
          Scn_Stream pStream, c_string cTokNam, c_string cTokVal, symbol* cMacVal
        )

preprocesses current token of non-binary scan stream 'pStream'
'cTokNam': name of separated token
'cTokVal': value of separated token
'cMacVal': preprocessing result ( see [scn_base] )
( cTokNam, cTokVal: single byte or utf-8 characterset )