go: add step8_macros

7 files changed, 346 insertions, 12 deletions

diff --git a/go/Makefile b/go/Makefile
index ddf29f6..dbdfeaf 100644
--- a/go/Makefile
+++ b/go/Makefile
@@ -4,13 +4,14 @@ export GOPATH := $(dir $(abspath $(lastword $(MAKEFILE_LIST))))
 
 SOURCES_BASE = src/types/types.go src/reader/reader.go src/printer/printer.go \
 	       src/env/env.go src/core/core.go
-SOURCES_LISP = src/step7_quote/step7_quote.go
+SOURCES_LISP = src/step8_macros/step8_macros.go
 SOURCES = $(SOURCES_BASE) $(SOURCES_LISP)
 
 #####################
 
 SRCS = step0_repl.go step1_read_print.go step2_eval.go step3_env.go \
-       step4_if_fn_do.go step5_tco.go step6_file.go step7_quote.go
+       step4_if_fn_do.go step5_tco.go step6_file.go step7_quote.go \
+       step8_macros.go
 BINS = $(SRCS:%.go=%)
 
 #####################
diff --git a/go/src/core/core.go b/go/src/core/core.go
index 65475bb..3c6693e 100644
--- a/go/src/core/core.go
+++ b/go/src/core/core.go
@@ -50,12 +50,35 @@ func cons(a []MalType) (MalType, error) {
 }
 
 func concat(a []MalType) (MalType, error) {
-    lst1, e := GetSlice(a[0]); if e != nil { return nil, e }
-    lst2, e := GetSlice(a[1]); if e != nil { return nil, e }
+    if len(a) == 0 { return List{}, nil }
+    slc1, e := GetSlice(a[0]); if e != nil { return nil, e }
+    for i := 1; i < len(a); i+=1 {
+        slc2, e := GetSlice(a[i]); if e != nil { return nil, e }
+        slc1 = append(slc1, slc2...)
+    }
+    return List{slc1}, nil
+}
+
+func nth(a []MalType) (MalType, error) {
+    slc, e := GetSlice(a[0]); if e != nil { return nil, e }
+    idx := a[1].(int)
+    return slc[idx], nil
+}
 
-    return List{append(lst1, lst2...)}, nil
+func first(a []MalType) (MalType, error) {
+    if len(a) == 0 { return nil, nil }
+    slc, e := GetSlice(a[0]); if e != nil { return nil, e }
+    if len(slc) == 0 { return nil, nil }
+    return slc[0], nil
 }
 
+func rest(a []MalType) (MalType, error) {
+    slc, e := GetSlice(a[0]); if e != nil { return nil, e }
+    if len(slc) == 0 { return List{}, nil }
+    return List{slc[1:]}, nil
+}
+
+
 func empty_Q(a []MalType) (MalType, error) {
     switch obj := a[0].(type) {
     case List:   return len(obj.Val) == 0, nil
@@ -112,6 +135,9 @@ var NS = map[string]MalType{
 
     "cons": cons,
     "concat": concat,
+    "nth": nth,
+    "first": first,
+    "rest": rest,
     "empty?": empty_Q,
     "count": count,
     }
diff --git a/go/src/step5_tco/step5_tco.go b/go/src/step5_tco/step5_tco.go
index 0c07316..ad4b5e2 100644
--- a/go/src/step5_tco/step5_tco.go
+++ b/go/src/step5_tco/step5_tco.go
@@ -123,7 +123,9 @@ func EVAL(ast MalType, env EnvType) (MalType, error) {
             ast = a2
         }
     case "fn*":
-        fn := MalFunc{EVAL, a2, env, a1}
+        fn := MalFunc{EVAL, a2, env, a1, false,
+            func(outer EnvType, binds []MalType, exprs []MalType) (EnvType, error) {
+                return NewEnv(outer, binds, exprs) }}
         return fn, nil
     default:
         el, e := eval_ast(ast, env)
diff --git a/go/src/step6_file/step6_file.go b/go/src/step6_file/step6_file.go
index ddf748e..046f24e 100644
--- a/go/src/step6_file/step6_file.go
+++ b/go/src/step6_file/step6_file.go
@@ -123,7 +123,9 @@ func EVAL(ast MalType, env EnvType) (MalType, error) {
             ast = a2
         }
     case "fn*":
-        fn := MalFunc{EVAL, a2, env, a1}
+        fn := MalFunc{EVAL, a2, env, a1, false,
+            func(outer EnvType, binds []MalType, exprs []MalType) (EnvType, error) {
+                return NewEnv(outer, binds, exprs) }}
         return fn, nil
     default:
         el, e := eval_ast(ast, env)
diff --git a/go/src/step7_quote/step7_quote.go b/go/src/step7_quote/step7_quote.go
index 2acc9c7..8642cf0 100644
--- a/go/src/step7_quote/step7_quote.go
+++ b/go/src/step7_quote/step7_quote.go
@@ -156,7 +156,9 @@ func EVAL(ast MalType, env EnvType) (MalType, error) {
             ast = a2
         }
     case "fn*":
-        fn := MalFunc{EVAL, a2, env, a1}
+        fn := MalFunc{EVAL, a2, env, a1, false,
+            func(outer EnvType, binds []MalType, exprs []MalType) (EnvType, error) {
+                return NewEnv(outer, binds, exprs) }}
         return fn, nil
     default:
         el, e := eval_ast(ast, env)
diff --git a/go/src/step8_macros/step8_macros.go b/go/src/step8_macros/step8_macros.go
new file mode 100644
index 0000000..12f036a
--- /dev/null
+++ b/go/src/step8_macros/step8_macros.go
@@ -0,0 +1,282 @@
+package main
+
+import (
+    "bufio"
+    //"io"
+    "fmt"
+    "os"
+    "strings"
+    "errors"
+)
+
+import (
+    . "types"
+    "reader"
+    "printer"
+    . "env"
+    "core"
+)
+
+// read
+func READ(str string) (MalType, error) {
+    return reader.Read_str(str)
+}
+
+// eval
+func is_pair(x MalType) bool {
+    slc, e := GetSlice(x)
+    if e != nil { return false }
+    return len(slc) > 0
+}
+
+func quasiquote(ast MalType) MalType {
+    if !is_pair(ast) {
+        return List{[]MalType{Symbol{"quote"}, ast}}
+    } else {
+        slc, _ := GetSlice(ast)
+        a0 := slc[0]
+        if Symbol_Q(a0) && (a0.(Symbol).Val == "unquote") {
+            return slc[1]
+        } else if is_pair(a0) {
+            slc0, _ := GetSlice(a0)
+            a00 := slc0[0]
+            if Symbol_Q(a00) && (a00.(Symbol).Val == "splice-unquote") {
+                return List{[]MalType{Symbol{"concat"},
+                                      slc0[1],
+                                      quasiquote(List{slc[1:]})}}
+            }
+        }
+        return List{[]MalType{Symbol{"cons"},
+                              quasiquote(a0),
+                              quasiquote(List{slc[1:]})}}
+    }
+}
+
+func is_macro_call(ast MalType, env EnvType) bool {
+    if List_Q(ast) {
+        slc, _ := GetSlice(ast)
+        a0 := slc[0]
+        if Symbol_Q(a0) && env.Find(a0.(Symbol).Val) != nil {
+            mac, e := env.Get(a0.(Symbol).Val)
+            if e != nil { return false }
+            if MalFunc_Q(mac) {
+                return mac.(MalFunc).GetMacro()
+            }
+        }
+    }
+    return false
+}
+
+func macroexpand(ast MalType, env EnvType)  (MalType, error) {
+    var mac MalType
+    var e error
+    for ; is_macro_call(ast, env) ; {
+        slc, _ := GetSlice(ast)
+        a0 := slc[0]
+        mac, e = env.Get(a0.(Symbol).Val); if e != nil { return nil, e }
+        fn := mac.(MalFunc)
+        ast, e = fn.Apply(slc[1:]); if e != nil { return nil, e }
+    }
+    return ast, nil
+}
+
+func eval_ast(ast MalType, env EnvType) (MalType, error) {
+    //fmt.Printf("eval_ast: %#v\n", ast)
+    if Symbol_Q(ast) {
+        return env.Get(ast.(Symbol).Val)
+    } else if List_Q(ast) {
+        lst := []MalType{}
+        for _, a := range ast.(List).Val {
+            exp, e := EVAL(a, env)
+            if e != nil { return nil, e }
+            lst = append(lst, exp)
+        }
+        return List{lst}, nil
+    } else if Vector_Q(ast) {
+        lst := []MalType{}
+        for _, a := range ast.(Vector).Val {
+            exp, e := EVAL(a, env)
+            if e != nil { return nil, e }
+            lst = append(lst, exp)
+        }
+        return Vector{lst}, nil
+    } else if Hash_Map_Q(ast) {
+        m := ast.(map[string]MalType)
+        new_hm := map[string]MalType{}
+        for k, v := range m {
+            ke, e1 := EVAL(k, env)
+            if e1 != nil { return nil, e1 }
+            if _, ok := ke.(string); !ok {
+                return nil, errors.New("non string hash-map key")
+            }
+            kv, e2 := EVAL(v, env)
+            if e2 != nil { return nil, e2 }
+            new_hm[ke.(string)] = kv
+        }
+        return new_hm, nil
+    } else {
+        return ast, nil
+    }
+}
+
+func EVAL(ast MalType, env EnvType) (MalType, error) {
+    var e error
+    for {
+
+    //fmt.Printf("EVAL: %v\n", printer.Pr_str(ast, true))
+    switch ast.(type) {
+    case List: // continue
+    default:   return eval_ast(ast, env)
+    }
+
+    // apply list
+    ast, e = macroexpand(ast, env); if e != nil { return nil, e }
+    if (!List_Q(ast)) { return ast, nil }
+
+    a0 := ast.(List).Val[0]
+    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]
+    }
+    a0sym := "__<*fn*>__"
+    if Symbol_Q(a0) { a0sym = a0.(Symbol).Val } 
+    switch a0sym {
+    case "def!":
+        res, e := EVAL(a2, env)
+        if e != nil { return nil, e }
+        return env.Set(a1.(Symbol).Val, res), nil
+    case "let*":
+        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)
+            if e != nil { return nil, e }
+            let_env.Set(arr1[i].(Symbol).Val, exp)
+        }
+        ast = a2
+        env = let_env
+    case "quote":
+        return a1, nil
+    case "quasiquote":
+        ast = quasiquote(a1)
+    case "defmacro!":
+        fn, e := EVAL(a2, env)
+        fn = fn.(MalFunc).SetMacro()
+        if e != nil { return nil, e }
+        return env.Set(a1.(Symbol).Val, fn), nil
+    case "macroexpand":
+        return macroexpand(a1, env)
+    case "do":
+        lst := ast.(List).Val
+        _, e := eval_ast(List{lst[1:len(lst)-1]}, env) 
+        if e != nil { return nil, e }
+        if len(lst) == 1 { return nil, nil }
+        ast = lst[len(lst)-1]
+    case "if":
+        cond, e := EVAL(a1, env)
+        if e != nil { return nil, e }
+        if cond == nil || cond == false {
+            if len(ast.(List).Val) >= 4 {
+                ast = ast.(List).Val[3]
+            } else {
+                return nil, nil
+            }
+        } else {
+            ast = a2
+        }
+    case "fn*":
+        fn := MalFunc{EVAL, a2, env, a1, false,
+            func(outer EnvType, binds []MalType, exprs []MalType) (EnvType, error) {
+                return NewEnv(outer, binds, exprs) }}
+        return fn, nil
+    default:
+        el, e := eval_ast(ast, env)
+        if e != nil { return nil, e }
+        f := el.(List).Val[0]
+        if MalFunc_Q(f) {
+            fn := f.(MalFunc)
+            ast = fn.Exp
+            env, e = NewEnv(fn.Env, fn.Params.(List).Val, el.(List).Val[1:])
+            if e != nil { return nil, e }
+        } else {
+            fn, ok := f.(func([]MalType)(MalType, error))
+            if !ok { return nil, errors.New("attempt to call non-function") }
+            return fn(el.(List).Val[1:])
+        }
+    }
+
+    } // TCO loop
+}
+
+// print
+func PRINT(exp MalType) (string, error) {
+    return printer.Pr_str(exp, true), nil
+}
+
+
+var repl_env, _ = NewEnv(nil, nil, nil)
+
+// repl
+func rep(str string) (MalType, error) {
+    var exp MalType
+    var res string
+    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 res, e = PRINT(exp); e != nil { return nil, e }
+    return res, nil
+}
+
+func main() {
+    // core.go: defined using go
+    for k, v := range core.NS {
+        repl_env.Set(k, v)
+    }
+    repl_env.Set("eval", func(a []MalType) (MalType, error) {
+        return EVAL(a[0], repl_env) })
+    repl_env.Set("*ARGV*", List{})
+
+    // core.mal: defined using the language itself
+    rep("(def! not (fn* (a) (if a false true)))")
+    rep("(def! load-file (fn* (f) (eval (read-string (str \"(do \" (slurp f) \")\")))))")
+
+    // called with mal script to load and eval
+    if len(os.Args) > 1 {
+        args := make([]MalType, 0, len(os.Args)-2)
+        for _,a := range os.Args[2:] {
+            args = append(args, a)
+        }
+        repl_env.Set("*ARGV*", List{args})
+        rep("(load-file \"" + os.Args[1] + "\")")
+        os.Exit(0)
+    }
+
+    rdr := bufio.NewReader(os.Stdin);
+    // repl loop
+    for {
+        fmt.Print("user> ");
+        text, err := rdr.ReadString('\n');
+        text = strings.TrimRight(text, "\n");
+        if (err != nil) {
+            return
+        }
+        var out MalType
+        var e error
+        if out, e = rep(text); e != nil {
+            if e.Error() == "<empty line>" { continue }
+            fmt.Printf("Error: %v\n", e)
+            continue
+        }
+        fmt.Printf("%v\n", out)
+    }
+}
diff --git a/go/src/types/types.go b/go/src/types/types.go
index f0ab427..c79810f 100644
--- a/go/src/types/types.go
+++ b/go/src/types/types.go
@@ -35,10 +35,12 @@ func Symbol_Q(obj MalType) bool {
 
 // Functions
 type MalFunc struct {
-    Eval   func(MalType, EnvType) (MalType, error)
-    Exp    MalType
-    Env    EnvType
-    Params MalType
+    Eval    func(MalType, EnvType) (MalType, error)
+    Exp     MalType
+    Env     EnvType
+    Params  MalType
+    IsMacro bool
+    GenEnv  func(EnvType, []MalType, []MalType) (EnvType, error)
 }
 
 func MalFunc_Q(obj MalType) bool {
@@ -48,6 +50,23 @@ func MalFunc_Q(obj MalType) bool {
     }
 }
 
+func (f MalFunc) SetMacro() MalType {
+    f.IsMacro = true
+    return f
+}
+
+func (f MalFunc) GetMacro() bool {
+    return f.IsMacro
+}
+
+func (f MalFunc) Apply(a []MalType) (MalType, error) {
+    slc, e := GetSlice(f.Params)
+    if e != nil { return nil, e }
+    env, e := f.GenEnv(f.Env, slc, a)
+    if e != nil { return nil, e }
+    return f.Eval(f.Exp, env)
+}
+
 
 // Lists
 type List struct {