Incomplete Support for Preprocessor Directives

[code-with-parth]

Description:
The current implementation of the translator does not fully support all HLSL/Cg preprocessor directives (e.g., #ifdef, #elif, #undef). This results in translation failures or incorrect handling of conditional compilation blocks, which are essential for writing modular and reusable shader code.

Steps to Reproduce:

1. Write an HLSL shader using a preprocessor directive such as #elif or #undef.

2. Translate the shader using CrossGL.

3. Observe that the translation fails or generates incorrect code.

Expected Behavior:
The translator should correctly interpret and translate all standard preprocessor directives to the target shading language.

Actual Behavior:
The translation either fails or skips conditional blocks, leading to broken or incomplete output shaders.

Environment Details:

OS: macOS Ventura 13.2

DirectX Version: 11

Python Version: 3.9

Additional Context:

The lexer.py and parser.py files currently handle basic directives (#define, #include, #ifdef), but directives like #elif and #undef are not supported.

This issue hinders developers from using flexible, conditional shader logic effectively.

[code-with-parth]

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