add impl constant

DNCL3.js

@@ -5,6 +5,14 @@ const reserved = [
 
 const isNumber = (c) => "0123456789".indexOf(c) >= 0;
 const isOperator = (c) => "+-*/%=!<>,".indexOf(c) >= 0;
+const isUpperAlphabet = (c) => "ABCDEFGHIJKLMNOPQRSTUVWXYZ".indexOf(c) >= 0;
+
+const isConstantName = (s) => {
+  for (const c of s) {
+    if (!isUpperAlphabet(c) && c != "_") return false;
+  }
+  return true;
+};
 
 export class DNCL3 {
   constructor(s, callbackoutput) {
@@ -276,6 +284,7 @@ export class DNCL3 {
         const op = this.getToken();
         if (op.type != "operator" || op.operator != "=") throw new Error("代入は変数の後に = で続ける必要があります");
         const val = this.getExpression();
+        if (isConstantName(token2.name) && this.vars[token2.name] !== undefined) throw new Error("定数には再代入できません");
         this.vars[token2.name] = val;
 
         const op2 = this.getToken();

DNCL3.test.js

@@ -17,3 +17,8 @@ Deno.test("var", () => {
   t.assertEquals(run("a = 1\nb = 2\nc = a + b\nprint c"), ["3"]);
   t.assertEquals(run(`a = "1"\nb = "2"\nc = a + b\nprint c`), ["12"]);
 });
+Deno.test("const", () => {
+  t.assertEquals(run("A = 1\nprint A"), ["1"]);
+  t.assertThrows(() => run("A = 1\nA = 2"));
+  t.assertEquals(run("Aa = 1\nAa = 2\nprint Aa"), ["2"]);
+});

README.md

@@ -8,7 +8,7 @@ deno run -A DNCL3.example.js bmi
 ```
 
 ※ TODO: 下記は未実装です
-- 定数 / 配列 / input / 複数行if / while / do / until / for / function / return
+- 配列 / input / 複数行if / while / do / until / for / function / return
 
 ## 1 変数と値
 

examples/const.dncl3

@@ -0,0 +1,2 @@
+A = 3.2
+A = 5