counterpoint-engine-c

C99 port of counterpoint-engine-rs — species counterpoint rule checker with interval classification, first-species rules, and consonance scoring.

What This Gives You

• Interval classification — Consonance (perfect/imperfect) and dissonance detection
• First species rules — Parallel 5ths/octaves, voice crossing, leap limits
• Scoring — Consonance ratio minus violation penalties, with configurable thresholds
• Zero dependencies — C99, only <math.h> and <stdlib.h>

Quick Start

#include "counterpoint_engine.h"

int cf[] = {60, 62, 64, 65, 67};  /* C D E F G */
int cp[] = {64, 65, 67, 69, 71};  /* E F G A B */
VoicePair vp = voice_pair_new(cf, cp, 5);

CounterpointChecker checker = checker_default();
CheckResult result = checker_check(&checker, &vp);

if (check_result_is_valid(&result)) {
    printf("Valid! Score: %.2f\n", result.score);
}

Build & Test

make            # build static library
make test       # build and run tests
make clean

API Reference

Function	Description
voice_pair_new(cf, cp, n)	Create a cantus firmus + counterpoint pair
checker_default()	Default rule checker
checker_check(&checker, &vp)	Evaluate all rules, return CheckResult
check_result_is_valid(&result)	Did the pair pass all rules?
result.score	Consonance score (higher = better)
result.violations	Array of Violation structs

How It Fits

• counterpoint-engine-rs — The Rust original; this is the C port
• constraint-instrument — Counterpoint rules feed into constraint terrain definitions
• flux-algebra-c — Harmonic analysis for counterpoint evaluation
• creative-engine-c — Chaotic dynamics for generating candidate counterpoint lines

Testing

10 tests covering interval classification, consonance detection, parallel fifth/octave rules, voice crossing, and scoring.

make test

Installation

git clone https://github.com/SuperInstance/counterpoint-engine-c.git
cd counterpoint-engine-c
make

License

MIT

Part of the SuperInstance OpenConstruct ecosystem.