Add short first doc paragraph (#153)

* Add short first doc paragraph

* Fix some more first doc paragraphs

src/fret_pattern.rs

@@ -8,6 +8,7 @@ use crate::{FretID, STRING_COUNT};
 pub struct ParseFretPatternError;
 
 /// A pattern of frets to press down for playing a chord.
+///
 /// Each index of the array corresponds to a ukulele string.
 #[derive(Debug, Copy, Clone)]
 pub struct FretPattern {

src/interval.rs

@@ -10,6 +10,7 @@ pub struct ParseIntervalError {
 }
 
 /// An interval is the difference between two notes.
+///
 /// https://en.wikipedia.org/wiki/Interval_(music)
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Interval {

src/staff_position.rs

@@ -5,6 +5,7 @@ use crate::StaffSteps;
 const STAFF_POSITION_COUNT: StaffSteps = 7;
 
 /// The vertical position of the notehead on the staff (on a line or in a space).
+///
 /// We use the staff position of an enharmonic note to decide whether it is sharp
 /// or flat.
 ///

src/voicing.rs

@@ -12,15 +12,17 @@ use crate::{
     FINGER_COUNT, STRING_COUNT,
 };
 
+/// A chord voicing.
+///
+/// The voicing of a chord describes the order of the individual notes within
+/// the chord. The same chord can be voiced in different ways, i.e. there are
+/// several ways to play the same chord on the ukulele.
+/// https://en.wikipedia.org/wiki/Voicing_(music)
 #[derive(Clone, Copy, PartialEq, Eq)]
 pub struct Voicing {
     uke_strings: [UkeString; STRING_COUNT],
 }
 
-/// The voicing of a chord describes the order of the individual notes within
-/// the chord. The same chord can be voiced in different ways, i.e. there are
-/// several ways to play the same chord on the ukulele.
-/// https://en.wikipedia.org/wiki/Voicing_(music)
 impl Voicing {
     // Create a Voicing instance from a set of frets and a tuning.
     // As there is no information about a certain chord for which

src/voicing_graph.rs

@@ -7,7 +7,9 @@ use crate::{Chord, ChordSequence, Distance, Semitones, Voicing, VoicingConfig};
 
 const MAX_DIST: Semitones = 10;
 
-/// A graph whose nodes represent chord voicings and whose edges
+/// A graph of voicings to find the optimal voice leading.
+///
+/// The nodes of the graph represent chord voicings and its edges
 /// are weighted by the distances between the voicings. It is used
 /// to find the (by some definition) optimal voice leading for
 /// a given sequence of chords.