From 4cd4d9080d60bb7e8638e7ef5a4fd792ecdaebdc Mon Sep 17 00:00:00 2001
From: Maxwell Jeffress <maxwelljeffress@proton.me>
Date: Wed, 13 Aug 2025 09:40:03 +1000
Subject: [PATCH] Function declarations

---
 src/main.cpp         | 114 +++++++++++++++++++++++++++++++++++++------
 tests/functions.grnd |   6 +++
 2 files changed, 104 insertions(+), 16 deletions(-)
 create mode 100644 tests/functions.grnd

diff --git a/src/main.cpp b/src/main.cpp
index c8d5e9b..a73f1fd 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -144,15 +144,6 @@ struct TypeRef {
 struct FunctionRef {
     string fnName;
 };
-/*
-    Function struct
-    Contains information needed to run a Ground function.
-*/
-struct Function {
-    int startPos;
-    Types returnType;
-    vector<pair<Direct, Types>> args;
-};
 
 /*
     ListRef struct
@@ -187,12 +178,6 @@ map<string, List> lists;
 */
 map<string, int> labels;
 
-/*
-    functions map
-    Contains the positions of functions and types of their values
-*/
-map<string, Function> functions;
-
 /*
     ValueRef struct
     If the program being executed makes a value reference, it is stored in a ValueRef
@@ -253,6 +238,22 @@ struct Instruction {
     vector<variant<Literal, ValueRef, ListRef, FunctionRef, TypeRef, Direct, Line>> args;
 };
 
+/*
+    Function struct
+    Contains information needed to run a Ground function.
+*/
+struct Function {
+    Types returnType;
+    vector<pair<Direct, Types>> args;
+    vector<Instruction> instructions;
+};
+
+/*
+    functions map
+    Contains the code of functions and types of their values
+*/
+map<string, Function> functions;
+
 /*
     error function
     Takes a string (which is a debug message) and prints it to the console, letting the
@@ -368,9 +369,23 @@ Types getType(string in) {
     function below) and acts upon their properties. This is the main interpreter
     function for the program.
 */
+
+bool processingFunction = false;
+string procFnName = "";
+
 void exec(vector<Instruction> in) {
     for (int i = 0; i < in.size(); i++) {
         Instruction l = in[i];
+        if (processingFunction) {
+            if (l.inst == Instructions::Endfun) {
+                processingFunction = false;
+                procFnName = "";
+                continue;
+            } else {
+                functions[procFnName].instructions.push_back(l);
+                continue;
+            }
+        }
         // Pre process value references and labels
         for (int j = 0; j < l.args.size(); j++) {
             if (holds_alternative<ValueRef>(l.args[j])) {
@@ -1386,7 +1401,7 @@ void exec(vector<Instruction> in) {
                 }
                 break;
             /*
-                end instructoin
+                end instruction
                 Ends execution of the code, eith the status code provided.
             */
             case Instructions::End:
@@ -1403,14 +1418,78 @@ void exec(vector<Instruction> in) {
                     error("First argument of end must be an int value");
                 }
                 break;
+            /*
+                fun instruction
+                Allows functions to be defined.
+            */
             case Instructions::Fun:
+                if (l.args.size() < 3) {
+                    error("Could not find all arguments required for Fun inbuilt");
+                }
+                {
+                    Function newFunction;
+                
+                    if (holds_alternative<TypeRef>(l.args[0])) {
+                        newFunction.returnType = get<TypeRef>(l.args[0]).type;
+                    } else {
+                        error("First argument of function must be a type reference");
+                    }
+
+                    string fnName;
+                    
+                    if (holds_alternative<FunctionRef>(l.args[1])) {
+                        fnName = get<FunctionRef>(l.args[1]).fnName;
+                    } else {
+                        error("Second argument of function must be a function reference");
+                    }
+
+                    Types argType;
+                    Direct ref;
+                    bool expectingType = true;
+                    for (int m = 2; m < l.args.size(); m++) {
+                        if (expectingType) {
+                            if (holds_alternative<TypeRef>(l.args[m])) {
+                                argType = get<TypeRef>(l.args[m]).type;
+                            } else {
+                                error("Functions expect a type reference, then a direct reference. Missing a type reference.");
+                            }
+                        } else {
+                            if (holds_alternative<Direct>(l.args[m])) {
+                                ref = get<Direct>(l.args[m]);
+                            } else {
+                                error("Functions expect a type reference, then a direct reference. Missing a direct reference.");
+                            }
+                            newFunction.args.push_back(pair(ref, argType));
+                        }
+                        expectingType = !expectingType;
+                    }
+                    
+                    if (!expectingType) {
+                        error("Incomplete function definition, expecting a direct reference after type reference");
+                    }
+
+                    functions[fnName] = newFunction;
+                    processingFunction = true;
+                    procFnName = fnName;
+                }
                 break;
+            /*
+                return instruction
+                Exits a function.
+            */
             case Instructions::Return:
                 break;
+            /*
+                endfun instruction
+                This should not be reached during normal execution. 
+            */
             case Instructions::Endfun:
+                error("No function is being defined. Cannot end function declaration here");
                 break;
             case Instructions::Pusharg:
                 break;
+            case Instructions::Local:
+                break;
             case Instructions::Call:
                 break;
             case Instructions::Use:
@@ -1580,6 +1659,8 @@ vector<Instruction> parser(vector<vector<string>> in) {
                             else if (type == "double") newType.type = Types::Double;
                             else if (type == "int") newType.type = Types::Int;
                             else if (type == "bool") newType.type = Types::Bool;
+                            else error("Ground could not find type. This is an error with the interpreter, not your code. This line of code should never be reached.");
+                            newInst.args.push_back(newType);
                         }
                         break;
                     case Types::Function:
@@ -1588,6 +1669,7 @@ vector<Instruction> parser(vector<vector<string>> in) {
                             newFunction.fnName = i.substr(1);
                             newInst.args.push_back(newFunction); 
                         }
+                        break;
                     case Types::Line:
                         {
                             Line newLine;
diff --git a/tests/functions.grnd b/tests/functions.grnd
new file mode 100644
index 0000000..906f18d
--- /dev/null
+++ b/tests/functions.grnd
@@ -0,0 +1,6 @@
+fun -int !dingle -string &silly
+stdlnout &silly
+return 10
+endfun
+
+stdlnout "This is outside the function"