From 619a2ed04e2430d791a14c4485be718f6c15234b Mon Sep 17 00:00:00 2001
From: Sami Samhuri <sami.samhuri@gmail.com>
Date: Wed, 20 Apr 2011 13:40:50 -0700
Subject: [PATCH] define math primitives + - * and /

---
 int.c  |   5 ---
 int.h  |   1 -
 lake.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 lake.h |   2 ++
 4 files changed, 108 insertions(+), 10 deletions(-)

diff --git a/int.c b/int.c
index a2d65b1..363f66f 100644
--- a/int.c
+++ b/int.c
@@ -40,11 +40,6 @@ LakeInt *int_from_c(int n)
     return i;
 }
 
-int int_val(LakeInt *i)
-{
-    return i->val;
-}
-
 LakeInt *int_cmp(LakeInt *a, LakeInt *b)
 {
     int aN = a->val, bN = b->val;
diff --git a/int.h b/int.h
index e972e50..dc1dc59 100644
--- a/int.h
+++ b/int.h
@@ -15,7 +15,6 @@
 LakeInt *int_make(void);
 LakeInt *int_copy(LakeInt *i);
 LakeInt *int_from_c(int n);
-int int_val(LakeInt *i);
 LakeInt *int_cmp(LakeInt *a, LakeInt *b);
 LakeBool *int_eq(LakeInt *a, LakeInt *b);
 LakeStr *int_to_str(LakeInt *i);
diff --git a/lake.c b/lake.c
index 2f0746f..acf1051 100644
--- a/lake.c
+++ b/lake.c
@@ -48,14 +48,116 @@ static LakeVal *prim_not(LakeList *args)
     return VAL(not);
 }
 
+static LakeVal *prim_add(LakeList *args)
+{
+    int result = 0;
+    size_t n = LIST_N(args);
+    size_t i;
+    for (i = 0; i < n; ++i) {
+        LakeVal *v = LIST_VAL(args, i);
+        if (!IS(TYPE_INT, v)) {
+            ERR("argument %zu is not an integer: %s", i, repr(v));
+            return NULL;
+        }
+        result += INT_VAL(INT(v));
+    }
+    return VAL(int_from_c(result));
+}
+
+static LakeVal *prim_sub(LakeList *args)
+{
+    size_t n = LIST_N(args);
+    
+    if (n < 1) {
+        ERR("- requires at least one argument");
+        return NULL;
+    }
+    
+    int result = 0;
+    size_t i;
+    for (i = 0; i < n; ++i) {
+        LakeVal *v = LIST_VAL(args, i);
+        if (!IS(TYPE_INT, v)) {
+            ERR("argument %zu is not an integer: %s", i, repr(v));
+            return NULL;
+        }
+        result -= INT_VAL(INT(v));
+    }
+    return VAL(int_from_c(result));
+}
+
+static LakeVal *prim_mul(LakeList *args)
+{
+    int result = 1;
+    size_t n = LIST_N(args);
+    size_t i;
+    for (i = 0; i < n; ++i) {
+        LakeVal *v = LIST_VAL(args, i);
+        if (!IS(TYPE_INT, v)) {
+            ERR("argument %zu is not an integer: %s", i, repr(v));
+            return NULL;
+        }
+        result *= INT_VAL(INT(v));
+    }
+    return VAL(int_from_c(result));
+}
+
+#define DIVIDE_BY_ZERO() ERR("divide by zero")
+
+static LakeVal *prim_div(LakeList *args)
+{
+    size_t n = LIST_N(args);
+    
+    if (n < 1) {
+        ERR("/ requires at least one argument");
+        return NULL;
+    }
+    
+    LakeVal *v = LIST_VAL(args, 0);
+    if (!IS(TYPE_INT, v)) {
+        ERR("argument 0 is not an integer: %s", repr(v));
+        return NULL;
+    }
+    int result = INT_VAL(INT(v));
+
+    if (n == 1) {
+        if (result == 0) {
+            DIVIDE_BY_ZERO();
+            return NULL;
+        }
+        result = 1 / result;
+    }
+    else {
+        size_t i;
+        for (i = 1; i < n; ++i) {
+            v = LIST_VAL(args, i);
+            if (!IS(TYPE_INT, v)) {
+                ERR("argument %zu is not an integer: %s", i, repr(v));
+                return NULL;
+            }
+            int val = INT_VAL(INT(v));
+            if (val == 0) {
+                DIVIDE_BY_ZERO();
+                return NULL;
+            }
+            result /= val;
+        }
+    }
+    return VAL(int_from_c(result));
+}
+
 static Env *primitive_bindings(void)
 {
-    #define DEFINE(name, arity, fn) env_define(env, sym_intern(name), VAL(prim_make(name, arity, fn)))
+    #define DEFINE(name, fn, arity) env_define(env, sym_intern(name), VAL(prim_make(name, arity, fn)))
     
     Env *env = env_toplevel();
-    DEFINE("null?", 1, prim_nullP);
-    DEFINE("pair?", 1, prim_pairP);
-    DEFINE("not", 1, prim_not);
+    DEFINE("null?", prim_nullP, 1);
+    DEFINE("pair?", prim_pairP, 1);
+    DEFINE("not", prim_not, 1);
+    DEFINE("+", prim_add, ARITY_VARARGS);
+    DEFINE("-", prim_sub, ARITY_VARARGS);
+    DEFINE("*", prim_mul, ARITY_VARARGS);
+    DEFINE("/", prim_div, ARITY_VARARGS);
     return env;
 }
 
diff --git a/lake.h b/lake.h
index 6622dcd..7e278f0 100644
--- a/lake.h
+++ b/lake.h
@@ -77,6 +77,8 @@ struct lake_int {
 };
 typedef struct lake_int LakeInt;
 
+#define INT_VAL(x) (x->val)
+
 struct lake_str {
     LakeVal base;
     size_t n;