fix: Constraint Sense should be an Enum of possible values

src/lp_parts.rs

@@ -5,7 +5,14 @@ use unique_id::{sequence::SequenceGenerator, Generator};
 
 use crate::{
     common::RuleExt,
-    model::{constraint::Constraint, lp_problem::LPProblem, objective::Objective, sense::Sense, sos::SOSClass, variable::VariableType},
+    model::{
+        constraint::Constraint,
+        lp_problem::LPProblem,
+        objective::Objective,
+        sense::{Cmp, Sense},
+        sos::SOSClass,
+        variable::VariableType,
+    },
     Rule,
 };
 
@@ -40,7 +47,7 @@ fn compose_constraint(pair: Pair<'_, Rule>, gen: &mut SequenceGenerator) -> anyh
     }
     let coefficients: anyhow::Result<Vec<_>> =
         coefficients.into_iter().filter(|p| !matches!(p.as_rule(), Rule::PLUS | Rule::MINUS)).map(|p| p.into_inner().try_into()).collect();
-    let sense = parts.next().unwrap().as_str().to_string();
+    let sense = Cmp::from_str(parts.next().unwrap().as_str())?;
     let rhs = parts.next().unwrap().as_str().parse()?;
     Ok(Constraint::Standard { name, coefficients: coefficients?, sense, rhs })
 }

src/model/constraint.rs

@@ -1,4 +1,4 @@
-use crate::model::{coefficient::Coefficient, sos::SOSClass};
+use crate::model::{coefficient::Coefficient, sense::Cmp, sos::SOSClass};
 
 #[derive(Debug, Clone)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
@@ -8,7 +8,7 @@ use crate::model::{coefficient::Coefficient, sos::SOSClass};
 )))]
 pub enum Constraint {
     /// Standard LP constraint
-    Standard { name: String, coefficients: Vec<Coefficient>, sense: String, rhs: f64 },
+    Standard { name: String, coefficients: Vec<Coefficient>, sense: Cmp, rhs: f64 },
     /// Special Order Set (SOS)
     SOS { name: String, kind: SOSClass, coefficients: Vec<Coefficient> },
 }

src/model/sense.rs

@@ -1,3 +1,5 @@
+use std::str::FromStr;
+
 #[derive(Debug, Default, PartialEq, Eq, Clone)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "diff", derive(diff::Diff))]
@@ -9,3 +11,33 @@ pub enum Sense {
     Minimize,
     Maximize,
 }
+
+#[derive(Debug, Default, PartialEq, Eq, Clone)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+#[cfg_attr(feature = "diff", derive(diff::Diff))]
+#[cfg_attr(feature = "diff", diff(attr(
+    #[derive(Debug, PartialEq, serde::Serialize, serde::Deserialize)]
+)))]
+pub enum Cmp {
+    #[default]
+    GreaterThan,
+    LessThan,
+    Equal,
+    GreaterOrEqual,
+    LessOrEqual,
+}
+
+impl FromStr for Cmp {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            ">=" => Ok(Self::GreaterOrEqual),
+            "<=" => Ok(Self::LessOrEqual),
+            ">" => Ok(Self::GreaterThan),
+            "<" => Ok(Self::LessThan),
+            "=" => Ok(Self::Equal),
+            _ => Err(anyhow::anyhow!("Unrecognized cmp: {s}")),
+        }
+    }
+}

tests/diff_feature.rs

@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 
 use lp_parser_rs::{
-    model::{coefficient::Coefficient, constraint::Constraint, lp_problem::LPProblem},
+    model::{coefficient::Coefficient, constraint::Constraint, lp_problem::LPProblem, sense::Cmp},
     parse::{parse_file, parse_lp_file},
 };
 
@@ -24,13 +24,13 @@ fn test_constraint() {
     let a = Constraint::Standard {
         name: "a".to_string(),
         coefficients: vec![Coefficient { var_name: "ca".to_string(), coefficient: 1.0 }],
-        sense: ">".to_string(),
+        sense: Cmp::GreaterThan,
         rhs: 1.0,
     };
     let b = Constraint::Standard {
         name: "b".to_string(),
         coefficients: vec![Coefficient { var_name: "ca".to_string(), coefficient: 1.0 }],
-        sense: ">".to_string(),
+        sense: Cmp::GreaterThan,
         rhs: 1.0,
     };
     insta::assert_yaml_snapshot!(a.diff(&a));

tests/snapshots/diff_feature__constraint-2.snap

@@ -5,6 +5,6 @@ expression: a.diff(&b)
 Standard:
   name: b
   coefficients: []
-  sense: ~
+  sense: NoChange
   rhs: 0
 

tests/snapshots/diff_feature__file_comparison-2.snap

@@ -19,7 +19,7 @@ constraints:
               changes:
                 - var_name: ~
                   coefficient: -1
-        sense: ~
+        sense: NoChange
         rhs: 0
   removed: []
 

tests/snapshots/diff_feature__file_comparison-3.snap

@@ -201,7 +201,7 @@ constraints:
               changes:
                 - var_name: __dummy
                   coefficient: 1
-        sense: "<="
+        sense: LessOrEqual
         rhs: 1
     "c1_0_0_1:":
       Standard:
@@ -306,7 +306,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_59_6_0
                   coefficient: 1
-        sense: "<="
+        sense: LessOrEqual
         rhs: 1
     "c1_9_4_4:":
       Standard:
@@ -339,7 +339,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_5_6_9
                   coefficient: 1
-        sense: "<="
+        sense: LessOrEqual
         rhs: 1
     "c2_0_0:":
       Standard:
@@ -404,7 +404,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_0_6_9
                   coefficient: 1
-        sense: "="
+        sense: Equal
         rhs: 1
     "c2_9_2:":
       Standard:
@@ -501,7 +501,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_9_6_9
                   coefficient: 1
-        sense: "="
+        sense: Equal
         rhs: 1
     "c3_0_10:":
       Standard:
@@ -524,7 +524,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_0_6_10
                   coefficient: 1
-        sense: "<="
+        sense: LessOrEqual
         rhs: 1
     "c3_9_9:":
       Standard:
@@ -547,7 +547,7 @@ constraints:
                   coefficient: 1
                 - var_name: x_9_6_9
                   coefficient: 1
-        sense: "<="
+        sense: LessOrEqual
         rhs: 1
   removed:
     - "c1:"