Finish implementing lambda application

src/vm/commands/call.ts

@@ -1,6 +1,6 @@
 import {Command, ParseContext, StrTerm} from "./command.js";
 import {LexInput} from "../lexer.js";
-import {StrVM} from "../vm.js";
+import {ExecutionError, StrVM} from "../vm.js";
 
 type CallData = {
     callable: StrTerm,
@@ -32,7 +32,7 @@ export class Call extends Command<CallData> {
 
     async execute(vm: StrVM, data: CallData): Promise<StrVM> {
         return vm.replaceContextMatchingTerm(ctx => ({
-            override: (s) => {
+            override: async () => {
                 // Resolve the callable and params
                 const callable = ctx.resolveLambda(data.callable)
                 const params = data.params.map(p => ctx.resolveRequired(p))
@@ -61,7 +61,27 @@ export class Call extends Command<CallData> {
                     }
                 }
 
-                return s
+                if ( params.length > callable.value.params.length ) {
+                    throw new ExecutionError(`Invalid lambda call. Found ${params.length} parameters (expected ${callable.value.params.length})`)
+                }
+
+                // Create a new child VM to execute the lambda in
+                return vm.runInChild(async (childVM, childCtx) => {
+                    // Shadow the parameters for the lambda in this scope and bind the values
+                    childCtx.inScope(scope => {
+                        for ( let i = 0; i < params.length; i += 1 ) {
+                            const paramLVal = callable.value.params[i]!
+                            const paramRVal = params[i]!
+                            scope.shadowValue(paramLVal, paramRVal)
+                        }
+                    })
+
+                    for ( const exec of callable.value.body ) {
+                        await exec.command.execute(childVM, exec.data)
+                    }
+
+                    return childCtx.getSubject()
+                })
             },
         }))
     }