Add primitive-functions, ability to work with Program

src/lang/primitive.ts

@@ -0,0 +1,57 @@
+import { Value } from "./eval/value";
+import { Implementation, Program } from "./program";
+import { ThrownRuntimeError } from "./eval/error";
+import { FunctionName } from "./expr";
+import { valueToString } from "./debug/value_show";
+
+// TODO: Primitive functions like +, -, *, div, <, <=, ==, mod
+
+export function installPrimitives(program: Program) {
+  function R(name: FunctionName, implementation: Implementation) {
+    Program.registerPrimitive(program, name, implementation);
+  }
+
+  // addition
+  R("+", (args: Value[]): Value => {
+    let sum = 0;
+    for (const arg of args) {
+      if (arg.tag !== "number") {
+        throw ThrownRuntimeError.error({ tag: "TypeMismatch", expected: "number", received: arg });
+      }
+      sum += arg.value;
+    }
+    return Value.number(sum);
+  });
+
+  // multiplication
+  R("*", (args: Value[]): Value => {
+    let product = 1;
+    for (const arg of args) {
+      if (arg.tag !== "number") {
+        throw ThrownRuntimeError.error({ tag: "TypeMismatch", expected: "number", received: arg });
+      }
+      product = product*arg.value;
+    }
+    return Value.number(product);
+  });
+
+  // string concat
+  R("++", (args: Value[]): Value => {
+    let sum = "";
+    for (const arg of args) {
+      if (arg.tag !== "string") {
+        throw ThrownRuntimeError.error({ tag: "TypeMismatch", expected: "number", received: arg });
+      }
+      sum += arg.value;
+    }
+    return Value.string(sum);
+  });
+
+  R("log", (args: Value[]): Value => {
+    for (const arg of args) {
+      console.log(valueToString(arg));
+    }
+    return Value.tuple([]);
+  });
+
+}