updates

src/main.cpp

@@ -20,8 +20,8 @@
     With the licence out of the way, let's begin!
 
     Ground is a programming language which takes some inspiration from
-    Assembly in it's design, but has higher level features (more types,
-    simpler IO, easier variables, etc) which make it easy to use.
+    Assembly in its design, but has higher level features (more types,
+    simpler IO, easier variables, etc) which makes it easy to use.
 
     Ground works even better if you write a programming language that
     compiles to Ground code. Ground is designed to have a similar
@@ -54,7 +54,7 @@ enum class Instructions {
     Add, Subtract, Multiply, Divide,
     Equal, Inequal, Greater, Lesser,
     End, Set, Empty,
-    Setlist, Getlistat, Setlistat, Getlistsize  
+    Setlist, Getlistat, Setlistat, Getlistsize, Listappend, Listprepend  
 };
 
 /*
@@ -531,6 +531,10 @@ void exec(vector<Instruction> in) {
                     }
                 }
                 break;
+            /*
+                setlistat instruction
+                This instruction sets an item in a list to be a certain value.
+            */
             case Instructions::Setlistat:
                 if (l.args.size() < 3) {
                     error("Could not find all arguments required for Setlistat inbuilt");
@@ -573,6 +577,37 @@ void exec(vector<Instruction> in) {
                     }
                 }
                 break;
+            /*
+                listappend instruction
+                This instruction appends an item to a list.
+            */
+            case Instructions::Listappend:
+                if (l.args.size() < 2) {
+                    error("Could not find all arguments required for Listappend inbuilt");
+                }
+                {
+                    ListRef listref;
+                    Literal value;
+
+                    if (holds_alternative<ListRef>(l.args[0])) {
+                        listref = get<ListRef>(l.args[0]);
+                    } else {
+                        error("Second argument of listappend must be a list reference");
+                    }
+
+                    if (holds_alternative<Literal>(l.args[1])) {
+                        value = get<Literal>(l.args[1]);
+                    } else {
+                        error("Second argument of listappend must be a direct reference");
+                    }
+
+                    if (lists.find(listref.listName) != lists.end()) {
+                        lists[listref.listName].val.push_back(value);
+                    } else {
+                        error("Unknown list: " + listref.listName);
+                    }
+                }
+                break;
             /*
                 getlistsize instruction
                 This instruction saves the size of a list in a variable.