Prologue is an extensible text preprocessor written in Python. It performs evaluation in a continuous stream, which allows it to run fast and keep a minimal memory footprint with few open file handles.

Directives can be easily added and removed to customise the behaviour of the preprocessor. By default the following directives are supported:

• define/undef - allows constants to be declared and undeclared
• if/elif/else/endif - conditional inclusion of blocks of text/other preprocessor directives
• ifdef/ifndef/else/endif - test whether constants are defined or undefined
• for/endfor - repeat a block of text for a number of iterations, can also iterate through an array
• info/warning/error - print messages to a log, or raise an exception, from a directive
• include/import - allows other files to be included or imported (one time include) into the stream

The easiest way to install Prologue is to use PyPI:

$> python3 -m pip install prologue

Alternatively, you can install the latest version directly from this repository:

$> python3 -m pip install git+git:https://github.com/Intuity/prologue

#define MY_VAL 123
#undef MY_VAL
#define MY_VAL 256

int main() {
#if MY_VAL > 200
    printf("Big value\n");
#else
    printf("Small value\n");
#endif
}

from prologue import Prologue
pro = Prologue()
pro.add_file("path/to/main.c")
for line in pro.evaluate("main.c"):
    print(line)

int main() {
    printf("Big value\n");
}

A number of examples are available in the examples folder:

• demo - is a demonstration of many features of Prologue, including loops, conditionals, include and import.
• c_style - demonstrates how Prologue can be setup to act like GCC's preprocessor.
• verilog - demonstrates how Prologue can be setup to act like a Verilog/SystemVerilog preprocessor.

Prologue comes with a suite of tests, which use pytest for regression:

$> git clone [email protected]:Intuity/prologue
$> cd prologue
$> python3 setup.py test

Some features that still need to be implemented are:

• Support for C-style substitution delimiters to provide separation - for example NUMBER_##A_CONST##_IS_THE_BEST
• Support for macro functions with nested support - for example #define SUM(A, B) A + B