Implement simple fn docstrings.

Adds usage of this new feature for pebblisp.pbl's (alias).

src/env.c

@@ -409,9 +409,10 @@ Object help(Object* params, int length, struct Environment* env)
             return text;
         }
     }
+
     Object* object = fetch(symbol, env);
     if (object) {
-        size_t len;
+        size_t len = 0;
         char* string = stringObj(object, &len);
         Object text = stringFromSlice(string, len);
         free(string);

src/examples/pebblisp.pbl

@@ -35,7 +35,8 @@
   (Alias "r" "(reloadConfig)")
 ))
 
-(def alias (fn () (
+(def alias (fn () 
+  "Get a string that lists all current aliases." (
     (reduce (map (fn (a) (cat nl a.name " -> " a.value)) aliases) cat "")
   )))
 

src/object.c

@@ -294,6 +294,11 @@ int stringNObj(struct string* s, const Object* obj)
 #ifdef DEBUG
             s->cursor += sprintf(s->cursor, "\\x%d", obj->number);
 #endif
+            char* docString = obj->lambda->params.docString;
+            if (docString) {
+                inflate(s, strlen(docString));
+                s->cursor += sprintf(s->cursor, "%s\n", docString);
+            }
             stringNObj(s, &obj->lambda->params);
             s->cursor += sprintf(s->cursor, " -> ");
             stringNObj(s, &obj->lambda->body);
@@ -418,6 +423,7 @@ void cleanObject(Object* target)
                 cleanObject(&target->lambda->params);
                 cleanObject(&target->lambda->body);
                 free(target->lambda);
+                free(target->lambda->params.docString);
             }
             break;
         case TYPE_STRUCT:
@@ -728,7 +734,7 @@ inline Object withLen(size_t len, enum Type type)
     return o;
 }
 
-inline Object constructLambda(const Object* params, const Object* body, struct Environment* env)
+inline Object constructLambda(const Object* params, const Object* docs, const Object* body, struct Environment* env)
 {
     if (!params || !body) {
         return errorObject(NULL_LAMBDA_LIST);
@@ -738,12 +744,23 @@ inline Object constructLambda(const Object* params, const Object* body, struct E
         return errorObject(LAMBDA_ARGS_NOT_LIST);
     }
 
+    if (docs && docs->type != TYPE_STRING) {
+        return errorWithContext(BAD_TYPE, "fn docstring must be a string");
+    }
+
     Object o = newObject(TYPE_LAMBDA);
     o.lambda = malloc(sizeof(struct Lambda));
     o.lambda->params = copyList(params);
     o.lambda->body = copyList(body);
     o.lambda->refs = 1;
 
+    if (docs) {
+        o.lambda->params.docString = malloc(sizeof(char) * (strlen(docs->string) + 1));
+        strcpy(o.lambda->params.docString, docs->string);
+    } else {
+        o.lambda->params.docString = NULL;
+    }
+
     Object* dest = &o.lambda->body;
     FOR_POINTER_IN_LIST(dest) {
         if (POINTER->type == TYPE_SYMBOL) {

src/object.h

@@ -125,6 +125,7 @@ struct StructObject {
 
 struct Lambda {
     int refs;
+    /// Note: params.docstring can contain details about the constructed lambda.
     Object params;
     Object body;
 };
@@ -250,7 +251,7 @@ void errorAddContext(Object* o, const char* context, int lineNo, const char* fil
 
 struct Error noError();
 
-Object constructLambda(const Object* params, const Object* body, struct Environment* env);
+Object constructLambda(const Object* params, const Object* docs, const Object* body, struct Environment* env);
 
 #ifdef STANDALONE
 

src/pebblisp.c

@@ -226,8 +226,13 @@ Object evalList(const Object* obj, struct Environment* env)
             return evalIfArgs(first_form->forward, env);
         } else if (strcmp(first_form->string, "fn") == 0) {
             Object* params = first_form->forward;
-            Object* body = params ? params->forward : NULL;
+            Object* doc = NULL;
-            return constructLambda(params, body, env);
+            Object* body = NULL;
+            if (params) {
+                doc = params->forward && params->forward->forward ? params->forward : NULL;
+                body = doc ? params->forward->forward : params->forward;
+            }
+            return constructLambda(params, doc, body, env);
         } else if (strcmp(first_form->string, "struct") == 0) {
             return evalStructArgs(first_form->forward, first_form->forward->forward, env);
         }