go: add step4_if_fn_do

1 files changed, 17 insertions, 11 deletions

diff --git a/go/src/step3_env/step3_env.go b/go/src/step3_env/step3_env.go
index 6241eff..3d35dbe 100644
--- a/go/src/step3_env/step3_env.go
+++ b/go/src/step3_env/step3_env.go
@@ -70,30 +70,36 @@ func EVAL(ast MalType, env Env) (MalType, error) {
 
     // apply list
     a0 := ast.(List).Val[0]
-    if !Symbol_Q(a0) {
-        return nil, errors.New("attempt to apply on non-symbol '" +
-            printer.Pr_str(a0, true) + "'")
+    var a1 MalType = nil; var a2 MalType = nil
+    switch len(ast.(List).Val) {
+    case 1:
+        a1 = nil; a2 = nil
+    case 2:
+        a1 = ast.(List).Val[1]; a2 = nil
+    default:
+        a1 = ast.(List).Val[1]; a2 = ast.(List).Val[2]
     }
-    switch a0.(Symbol).Val {
+    a0sym := "__<*fn*>__"
+    if Symbol_Q(a0) { a0sym = a0.(Symbol).Val } 
+    switch a0sym {
     case "def!":
-        a1 := ast.(List).Val[1]; a2 := ast.(List).Val[2]
         res, e := EVAL(a2, env)
         if e != nil { return nil, e }
         return env.Set(a1.(Symbol).Val, res), nil
     case "let*":
-        a1 := ast.(List).Val[1]; a2 := ast.(List).Val[2]
-        let_env := NewEnv(&env, nil, nil)
+        let_env, e := NewEnv(&env, nil, nil)
+        if e != nil { return nil, e }
         arr1, e := GetSlice(a1)
         if e != nil { return nil, e }
         for i := 0; i < len(arr1); i+=2 {
             if !Symbol_Q(arr1[i]) {
                 return nil, errors.New("non-symbol bind value")
             }
-            exp, e := EVAL(arr1[i+1], let_env)
+            exp, e := EVAL(arr1[i+1], *let_env)
             if e != nil { return nil, e }
             let_env.Set(arr1[i].(Symbol).Val, exp)
         }
-        return EVAL(a2, let_env)
+        return EVAL(a2, *let_env)
     default:
         el, e := eval_ast(ast, env)
         if e != nil { return nil, e }
@@ -109,14 +115,14 @@ func PRINT(exp MalType) (MalType, error) {
 }
 
 
-var repl_env = NewEnv(nil, nil, nil)
+var repl_env, _ = NewEnv(nil, nil, nil)
 
 // repl
 func rep(str string) (MalType, error) {
     var exp MalType
     var e error
     if exp, e = READ(str); e != nil { return nil, e }
-    if exp, e = EVAL(exp, repl_env); e != nil { return nil, e }
+    if exp, e = EVAL(exp, *repl_env); e != nil { return nil, e }
     if exp, e = PRINT(exp); e != nil { return nil, e }
     return exp, nil
 }