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Macros#

goboscript has a C-like preprocessor. This allows you to define macros and include files.

Note

The preprocessor directives start with a % character. The % character must always appear at the start of a line. There cannot be any indentation before the % character.

Include#

Include the contents of a file.

%include path/to/file.gs

The .gs extension is optional. If not specified (recommended), the file extension will be added automatically.

If the include path is a directory, the file inside the directory with the same name as the directory will be included.

By default, the include path is relative to the project root directory. To include a file relative to the current file, use ./ or ../

Tip

bkpk.py is a small Python script that lets you include files from the internet using %include directives.

# run `./bkpk.py` to compile your project, instead of `goboscript build`
%include https://github.com/username/repo/branchname/filename.gs

Define#

Define a macro. That identifier will be substituted with the subsequent text.

%define macro_name replacement text

Define with arguments#

Define a macro with arguments. The arguments will be substituted with the tokens from the callsite.

%define macro_name(arg1, arg2) replacement text

Since () are interpreted as function parameter brackets, use double parentheses to include them in the expansion:

%define foo ((1 + 2))

This expands to ((1 + 2)), allowing you to control operator precedence in macro substitutions.

Use \ at the end of a line to continue the replacement text across multiple lines:

%define long_macro this is a very long \
                   replacement text that spans \
                   multiple lines

Define with overloaded arguments#

Macros with arguments can be overloaded by defining multiple versions with different numbers of arguments. The correct version will be selected based on the number of arguments passed at the callsite. 

%define MACRO(A) "MACRO(A)"
%define MACRO(A, B) "MACRO(A, B)"

onflag {
    say MACRO(1);      # expands to "MACRO(A)"
    say MACRO(1, 1);   # expands to "MACRO(A, B)"
}

Each overload is stored independently, so defining MACRO with one argument does not affect the definition of MACRO with two arguments. Using %undef macro_name removes all overloads for that name at once.

Remove a macro definition#

%undef macro_name

Conditional compilation#

%if macro_name
    code
%endif
%if not macro_name
    code
%endif

Concatenate Tokens#

CONCAT(prefix, suffix) # becomes prefixsuffix