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package main
import (
"fmt"
"strings"
"errors"
)
import (
"readline"
. "types"
"reader"
"printer"
. "env"
"core"
)
// read
func READ(str string) (MalType, error) {
return reader.Read_str(str)
}
// eval
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))
} 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}, 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}, nil
} else if HashMap_Q(ast) {
m := ast.(HashMap)
new_hm := HashMap{map[string]MalType{},nil}
for k, v := range m.Val {
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.Val[ke.(string)] = kv
}
return new_hm, nil
} else {
return ast, nil
}
}
func EVAL(ast MalType, env EnvType) (MalType, 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
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), 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), exp)
}
ast = a2
env = let_env
case "do":
lst := ast.(List).Val
_, e := eval_ast(List{lst[1:len(lst)-1],nil}, 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, NewEnv, nil}
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{el.(List).Val[1:],nil})
if e != nil { return nil, e }
} else {
fn, ok := f.(Func)
if !ok { return nil, errors.New("attempt to call non-function") }
return fn.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(Symbol{k}, Func{v.(func([]MalType)(MalType,error)),nil})
}
// core.mal: defined using the language itself
rep("(def! not (fn* (a) (if a false true)))")
// repl loop
for {
text, err := readline.Readline("user> ")
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)
}
}
|
