Condition Language

Condition language is a tiny boolean expression language written in minimal c++. It's weighs in around roughly 300 lines of code and is basically just a recursive decent parser with an execution and operator stack. It evaluates expressions during parsing and does not have any form of intermediate representation, making it perfect when you have lots of different conditions needing evaluation only once or a couple of times.

Example usage

// Our intrinsic function callback
bool equal(IdString32* params, unsigned n_params, void* user_data) {
    return params[0] == params[1];
}

condition_language::Intrinsic intrinsics[] = {
	{ your_hash_function("equal", 5), instrinsic::equal },
};
const unsigned num_intrinsics = sizeof(intrinsics) / sizeof(*intrinsics);
const char* source = "equal(A, A) && !!(equal(B, B) || equal(B, C))";

// A small execuion stack, 10 bytes would suffice for this expression.
unsigned char stack[16];
condition_language::Result r = condition_language::run(
	source,                     // Expression source
	stack, sizeof(stack),       // Execution stack memory
	intrinsics, num_intrinsics, // List of intrinsic functions
	your_hash_function,         // Hash function used for hashing intrinsic function arguments,
						        // must be the same as the one used to provice intrinsic funtion names.
	NULL);                      // User data pointer passed to the intrinsic function callbacks.
// The resulting value is available in r.value

Grammar

CONDITION :=
	LOGICAL '\0'

LOGICAL :=
	UNARY LOGICAL_REST

LOGICAL_REST :=
	'&&' LOGICAL
	'||' LOGICAL
	| ''

UNARY :=
	'!' UNARY
	| INTRINSIC

INTRINSIC :=
	IDENTIFIER '(' PARAMETERS ')'
	| '(' LOGICAL ')'

PARAMTERS :=
	IDENTIFIER PARAMETERS_REST

PARAMETERS_REST :=
	',' PARAMETERS
	| ''

License

It's released under the MIT license. Enjoy!

The MIT License (MIT)
Copyright (c) 2012 Jim Sagevid

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without restriction,
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 is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial
portions of the Software.

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