Sumi is an ink fork that adds advanced features to ink. These features include:

1. Ability to define function stitches. The original ink forbids using stitches as functions. In Sumi, you could call a stitch function via knot.stitchFunction(...), similar to how member functions are called in other languages. (note: there's no such thing as stitch in a stitch, so the maximum depth you can have is 1)

2. Use preprocessor directives (conditional compilation).

3. Struct definitions (WIP)

Usually these features are not required to make a game. We suggest that you get familiar with vanilla ink first then see if Sumi has features that seem interesting to you.

The syntax is similar to C# preprocessors:

#IF INKY
This will only be shown in Inky.
// you may use logical expressions as well
#ELIF ( UNITY && STEAM_BUILD ) || UNREAL
This will only be shown in Unity Stem Build or in Unreal.
#ELSE
This will be shown if not in Inky nor Unity.
#ENDIF

This is helpful if you are including libraries that might have different paths when editing with Inky and in runtime, or debug content.

#IF INKY
#INCLUDE "../InkLibs/Library.ink"
#ELSE
#INCLUDE "Library.ink"
#ENDIF

InkPreprocessor will resolve these directives after comment removal, and before compiling the main content. To keep line numbers intact, the preprocessor replaces masked out branches with line breaks, so you would end up with more empty line than you might expect. Hence, always check if a line has printable content before showing it to the player.

Caveat: The vanilla ink toolchain does not support preprocessor directives, so you will need to use a custom toolchain built from Sumi.

To specify preprocessor defines passed to the compiler, you could pass them via the constructor of the compiler:

var compiler = new Compiler (inkSource, new Compiler.Options {
    preprocessorSymbols = new()
    {
        "SOME_DEFINE", "SOME_OTHER_DEFINE"
    }
});

var story = compiler.Compile ();

Currently, if you make a mistake in preprocessor directives and result in a parse failure, the whole block will not be evaluated and all the directives will be treated as regular ink content (which will become tags).