From b443a54822bf84284816dca821ace21b928f1cd0 Mon Sep 17 00:00:00 2001
From: Sage Vaillancourt <sagev9000@tutanota.com>
Date: Thu, 29 Oct 2020 11:23:35 -0400
Subject: [PATCH] Add `pre` for prepending to lists

---
 src/env.c      | 3 ++-
 src/pebblisp.c | 8 ++++++++
 src/pebblisp.h | 1 +
 src/tests.sh   | 2 ++
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/env.c b/src/env.c
index 8e567c8..5ed0f35 100644
--- a/src/env.c
+++ b/src/env.c
@@ -192,7 +192,8 @@ struct Environment defaultEnv()
     struct symFunc symFuncs[] = {
         {"+", &add}, {"-", &sub}, {"*", &mul}, {"/", &dvi}, {"%", &mod},
         {"=", &equ}, {">", &gth}, {"<", &lth},
-        {"cat", &catObjects}, {"fil", &filter}, {"len", &len}, {"ap", &append},
+        {"cat", &catObjects}, {"fil", &filter}, {"len", &len},
+        {"ap", &append}, {"pre", &prepend},
         {"at", &at}, {"rest", &rest}, {"rev", &reverse},
         {"isnum", &isNum},
     };
diff --git a/src/pebblisp.c b/src/pebblisp.c
index 7138054..9634cdd 100644
--- a/src/pebblisp.c
+++ b/src/pebblisp.c
@@ -330,6 +330,14 @@ Object append(Object list, Object newElement, struct Environment *env)
     return newList;
 }
 
+Object prepend(Object list, Object newElement, struct Environment *env)
+{
+    Object newList = listObject();
+    nf_addToList(&newList, newElement);
+    appendList(&newList, &list);
+    return newList;
+}
+
 Object at(Object index, Object list, struct Environment *env)
 {
     return cloneObject(*itemAt(&list, index.number));
diff --git a/src/pebblisp.h b/src/pebblisp.h
index 6c9ac57..556bb80 100644
--- a/src/pebblisp.h
+++ b/src/pebblisp.h
@@ -50,6 +50,7 @@ BASIC_OP(gth); BASIC_OP(lth);
 Object catObjects(const Object obj1, const Object obj2, struct Environment *env);
 Object filter(Object obj1, Object obj2, struct Environment *env);
 Object append(Object list, Object newElement, struct Environment *env);
+Object prepend(Object list, Object newElement, struct Environment *env);
 Object at(Object index, Object list, struct Environment *env);
 Object rest(Object list, Object ignore, struct Environment *env);
 Object reverse(Object _list, Object ignore, struct Environment *ignore2);
diff --git a/src/tests.sh b/src/tests.sh
index 4689f16..967bb89 100755
--- a/src/tests.sh
+++ b/src/tests.sh
@@ -107,6 +107,8 @@ check "ListIndex" "(at (+ 1 1) (1 2 1000 4 5))" "1000"
 check "EvalElems" "((* 10 10) 7)" "( 100 7 )"
 check "AppendToList" "(ap (1 20 300 4000 50000) 600000)" "( 1 20 300 4000 50000 600000 )"
 check "AppndToEnvList" "(def l (50000 4000 300 20)) (def l (ap l 1)) l" "( 50000 4000 300 20 1 )"
+check "PrependToList" "(pre (1 20 300 4000 50000) 600000)" "( 600000 1 20 300 4000 50000 )"
+check "PrepndToEnvList" "(def l (50000 4000 300 20)) (def l (pre l 1)) l" "( 1 50000 4000 300 20 )"
 check "Rest(Tail)OfList" "(def l (50000 4000 300 20)) (rest l)" "( 4000 300 20 )"
 check "ListLength" "(def l (1 20 3 'abc' 'banana' (+ 10 5))) (len l)" "6"
 endBlock