first commit

java/expression/common/Expr.java

@@ -0,0 +1,32 @@
+package expression.common;
+
+import base.Functional;
+import base.Pair;
+
+import java.util.List;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+
+/**
+ * @author Georgiy Korneev (kgeorgiy@kgeorgiy.info)
+ */
+public record Expr<C, V>(Node<C> node, List<Pair<String, V>> variables) {
+    public <T> List<Pair<String, T>> variables(final BiFunction<String, V, T> f) {
+        return Functional.map(
+                variables,
+                variable -> variable.second(f.apply(variable.first(), variable.second()))
+        );
+    }
+
+    public <T> Expr<C, T> convert(final BiFunction<String, V, T> f) {
+        return of(node, variables(f));
+    }
+
+    public Expr<C, V> node(final Function<Node<C>, Node<C>> f) {
+        return of(f.apply(node), variables);
+    }
+
+    public static <C, V> Expr<C, V> of(final Node<C> node, final List<Pair<String, V>> variables) {
+        return new Expr<>(node, variables);
+    }
+}