Use plain functions for IntMap

Author: skylee03

course3/course_en.md

@@ -18,6 +18,19 @@ style: |
 <!--
 ```moonbit
 let pi = 3.1415
+
+fn put(map: @map.Map[Int, Int64], num: Int, result: Int64) -> @map.Map[Int, Int64] {
+  map.insert(num, result)
+}
+
+fn get(map: @map.Map[Int, Int64], num: Int) -> Option[Int64] {
+  map.lookup(num)
+}
+
+fn make() -> @map.Map[Int, Int64] {
+  @map.empty()
+}
+
 ```
 -->
 
@@ -594,9 +607,9 @@ A large number of duplicated subproblems was observed.
 - We need a data structure whose average access efficiency is independent of the data size, and it should have the following interfaces:
 
 ```moonbit no-check
-fn empty() -> IntMap                                      // Create
-fn insert(self: IntMap, key: Int, value: Int64) -> IntMap // Store
-fn lookup(self: IntMap, key: Int) -> Option[Int64]        // Retrieve
+fn make() -> IntMap                                   // Create
+fn put(map: IntMap, num: Int, value: Int64) -> IntMap // Store
+fn get(map: IntMap, num: Int) -> Option[Int64]        // Retrieve
 ```
 
 - There are many siutable data structures, e.g., `@map.Map[Int, Int64]`.
@@ -614,16 +627,16 @@ fn lookup(self: IntMap, key: Int) -> Option[Int64]        // Retrieve
 ```moonbit expr
 fn fib1(num: Int) -> Int64 {
   fn aux(num: Int, map: @map.Map[Int, Int64]) -> (Int64, @map.Map[Int, Int64]) {
-    match map.lookup(num) {
+    match get(map, num) {
       Some(result) => (result, map)
       None => {
         let (result_1, map_1) = aux(num - 1, map)
         let (result_2, map_2) = aux(num - 2, map_1)
-        (result_1 + result_2, map_2.insert(num, result_1 + result_2))
+        (result_1 + result_2, put(map_2, num, result_1 + result_2))
       }
     }
   }
-  let map = @map.empty().insert(1, 1L).insert(2, 1L)
+  let map = put(put(make(), 1, 1L), 2, 1L)
   aux(num, map).0
 }
 ```
@@ -638,15 +651,15 @@ To simplify the code, MoonBit supports mutable variables.
 ```moonbit expr
 fn fib1_mut(num: Int) -> Int64 {
   // Declare a mutable variable with let mut
-  let mut map = @map.empty().insert(1, 1L).insert(2, 1L)
+  let mut map = put(put(make(), 1, 1L), 2, 1L)
   fn aux(num: Int) -> Int64 {
-    match map.lookup(num) {
+    match get(map, num) {
       Some(result) => result
       None => {
         let result_1 = aux(num - 1)
         let result_2 = aux(num - 2)
         // Update the binding with <variable> = <expression>
-        map = map.insert(num, result_1 + result_2) 
+        map = put(map, num, result_1 + result_2) 
         result_1 + result_2
       }
     }
@@ -664,12 +677,12 @@ Starting from the first one, calculate and store the subsequent items sequential
 ```moonbit expr
 fn fib2(num: Int) -> Int64 {
   fn aux(n: Int, map: @map.Map[Int, Int64]) -> Int64 {
-    let result = get_or_else(map.lookup(n - 1), 1L) + 
-      get_or_else(map.lookup(n - 2), 1L)
-    if n == num { result }
-    else { aux(n + 1, map.insert(n, result)) }
+    let result = get_or_else(get(map, n - 1), 1L) + 
+      get_or_else(get(map, n - 2), 1L)
+    if n == num { result } 
+    else { aux(n + 1, put(map, n, result)) }
   }
-  let map = @map.empty().insert(0, 0L).insert(1, 1L)
+  let map = put(put(make(), 0, 0L), 1, 1L)
   aux(1, map)
 }
 ```

course3/lecture_en.md

@@ -3,6 +3,19 @@
 <!--
 ```moonbit
 let pi = 3.1415
+
+fn put(map: @map.Map[Int, Int64], num: Int, result: Int64) -> @map.Map[Int, Int64] {
+  map.insert(num, result)
+}
+
+fn get(map: @map.Map[Int, Int64], num: Int) -> Option[Int64] {
+  map.lookup(num)
+}
+
+fn make() -> @map.Map[Int, Int64] {
+  @map.empty()
+}
+
 ```
 -->
 
@@ -473,9 +486,9 @@ First, let's try a top-down implementation.
 To cache the previous calculation results, we need a suitable data structure. Since the number of results we cache will grow with the size of the problem, the average access efficiency of the data structure should be independent of the data size. Let's call it `IntMap`, then following our standard workflow, we should now define the interfaces:
 
 ```moonbit no-check
-fn empty() -> IntMap                                      // Create
-fn insert(self: IntMap, key: Int, value: Int64) -> IntMap // Store
-fn lookup(self: IntMap, key: Int) -> Option[Int64]        // Retrieve
+fn make() -> IntMap                                   // Create
+fn put(map: IntMap, num: Int, value: Int64) -> IntMap // Store
+fn get(map: IntMap, num: Int) -> Option[Int64]        // Retrieve
 ```
 
 In other words, we should be able to perform the following operations using an `IntMap`: create an empty map, insert a key-value pair into it, and look up the value corresponding to a given key.
@@ -487,16 +500,16 @@ In the top-down implementation, before each computation, we first check if our d
 ```moonbit expr
 fn fib1(num: Int) -> Int64 {
   fn aux(num: Int, map: @map.Map[Int, Int64]) -> (Int64, @map.Map[Int, Int64]) {
-    match map.lookup(num) {
+    match get(map, num) {
       Some(result) => (result, map)
       None => {
         let (result_1, map_1) = aux(num - 1, map)
         let (result_2, map_2) = aux(num - 2, map_1)
-        (result_1 + result_2, map_2.insert(num, result_1 + result_2))
+        (result_1 + result_2, put(map_2, num, result_1 + result_2))
       }
     }
   }
-  let map = @map.empty().insert(1, 1L).insert(2, 1L)
+  let map = put(put(make(), 1, 1L), 2, 1L)
   aux(num, map).0
 }
 ```
@@ -510,15 +523,15 @@ In MoonBit, all variables are immutable by default. In order to declare a mutabl
 ```moonbit expr
 fn fib1_mut(num: Int) -> Int64 {
   // Declare a mutable variable with let mut
-  let mut map = @map.empty().insert(1, 1L).insert(2, 1L)
+  let mut map = put(put(make(), 1, 1L), 2, 1L)
   fn aux(num: Int) -> Int64 {
-    match map.lookup(num) {
+    match get(map, num) {
       Some(result) => result
       None => {
         let result_1 = aux(num - 1)
         let result_2 = aux(num - 2)
         // Update the binding with <variable> = <expression>
-        map = map.insert(num, result_1 + result_2) 
+        map = put(map, num, result_1 + result_2) 
         result_1 + result_2
       }
     }
@@ -534,12 +547,12 @@ In the bottom-up implementation, we typically start from the smallest subproblem
 ```moonbit expr
 fn fib2(num: Int) -> Int64 {
   fn aux(n: Int, map: @map.Map[Int, Int64]) -> Int64 {
-    let result = get_or_else(map.lookup(n - 1), 1L) + 
-      get_or_else(map.lookup(n - 2), 1L)
-    if n == num { result }
-    else { aux(n + 1, map.insert(n, result)) }
+    let result = get_or_else(get(map, n - 1), 1L) + 
+      get_or_else(get(map, n - 2), 1L)
+    if n == num { result } 
+    else { aux(n + 1, put(map, n, result)) }
   }
-  let map = @map.empty().insert(0, 0L).insert(1, 1L)
+  let map = put(put(make(), 0, 0L), 1, 1L)
   aux(1, map)
 }
 ```