make format of docs for single checks more consistent

Author: intarga

src/checks/single/range_check.rs

@@ -1,9 +1,11 @@
 use crate::{DataCache, Flag};
 
-/// QC test that checks whether each observation fits within given (inclusive) limits.
+/// Single check of whether an observation fits within given (inclusive) limits.
 ///
-/// If the observation is missing, Flag::DataMissing with be returned, else if it is outside the
-/// upper or lower limits, Flag::Fail, else Flag::Pass.
+/// Returns:
+/// - [`Flag::DataMissing`] if the observation is missing,
+/// - [`Flag::Fail`] if it is outside the upper or lower limits,
+/// - [`Flag::Pass`] otherwise.
 pub fn range_check(datum: Option<f32>, lower_limit: f32, upper_limit: f32) -> Flag {
     match datum {
         None => Flag::DataMissing,

src/checks/single/range_check_humidity.rs

@@ -2,8 +2,11 @@ use crate::{DataCache, Flag};
 
 /// Range check with a correction for humidity over 100%.
 ///
-/// Humidity less than 5% or greater than 105% returns Flag::Fail, between 100% and 105% it is,
-/// corrected down to 100%.
+/// Returns:
+/// - ([`Flag::DataMissing`], None) if the observation is missing,
+/// - ([`Flag::Fail`], None) if humidity less than 5% or greater than 105%,
+/// - ([`Flag::Warn`], Some(100.)) between 100% and 105%,
+/// - ([`Flag::Pass`], None) otherwise.
 pub fn range_check_humidity(datum: Option<f32>) -> (Flag, Option<f32>) {
     match datum {
         None => (Flag::DataMissing, None),

src/checks/single/range_check_wind_direction.rs

@@ -2,8 +2,12 @@ use crate::{DataCache, Flag};
 
 /// Range check with a correction for wind direction outside 0-360.
 ///
-/// If the direction is -20-0, or 360-380, 360 will be added or subtracted to get it back into
-/// the correct range.
+/// Returns:
+/// - ([`Flag::DataMissing`], None) if the observation is missing,
+/// - ([`Flag::Fail`], None) if the value is less than -20 or greater than 380,
+/// - ([`Flag::Warn`], Some(value + 360)) if the value is between -20 and 0,
+/// - ([`Flag::Warn`], Some(value - 360)) if the value is between 360 and 380,
+/// - ([`Flag::Pass`], None) otherwise.
 pub fn range_check_wind_direction(datum: Option<f32>) -> (Flag, Option<f32>) {
     // TODO: get to the bottom of weird -3.0 handling: kvalobs code looks for a value -3.0, and
     // avoids flagging that if X_5 (lowest?) is also -3.0. From comments in the code, it looks like

src/checks/single/special_values_check.rs

@@ -1,9 +1,11 @@
 use crate::{DataCache, Flag};
 
-/// QC test that checks whether each observation matches some special values.
+/// Single check of whether an observation matches some special values.
 ///
-/// If the observation is missing, Flag::DataMissing with be returned, else if it is matches any of
-/// the special values, Flag::Fail, else Flag::Pass.
+/// Returns:
+/// - [`Flag::DataMissing`] if the observation is missing,
+/// - [`Flag::Fail`] if it matches any of the special values
+/// - [`Flag::Pass`] otherwise.
 pub fn special_values_check(datum: Option<f32>, special_values: &[f32]) -> Flag {
     match datum {
         None => Flag::DataMissing,