Implement (exit) and (forever)

This closes #133 - though there are no tests for either.

eval/eval.go

@@ -615,7 +615,7 @@ func (ev *Eval) eval(exp primitive.Primitive, e *env.Environment, expandMacro bo
 
 		// For each default argument set it
 		for k, v := range proc.Defaults {
-			e.Set(k.ToString(),v)
+			e.Set(k.ToString(), v)
 		}
 
 		// For each of the arguments that have been supplied

eval/eval_test.go

@@ -136,7 +136,6 @@ func TestEvaluate(t *testing.T) {
 		{"(fn* ( (3 3)   ) a )", "ERROR{expected a symbol for an argument, got 3}"},
 		{"(fn* ( (a 3 c) ) a )", "ERROR{only two list items allowed for a default-value, got 3}"},
 
-
 		// literals
 		{":foo", ":foo"},
 
@@ -451,7 +450,7 @@ a
 }
 
 // This function tests (read)
-func TestRead(t *testing.T ) {
+func TestRead(t *testing.T) {
 
 	tst := `(read)`
 
@@ -467,7 +466,7 @@ func TestRead(t *testing.T ) {
 
 	// Ensure we read from a fake input
 	c := config.DefaultIO()
-	c.STDIN = strings.NewReader( "hello, world\n")
+	c.STDIN = strings.NewReader("hello, world\n")
 
 	// Environment will have a config
 	ev.SetIOConfig(c)
@@ -479,14 +478,14 @@ func TestRead(t *testing.T ) {
 	out := l.Evaluate(ev)
 
 	if out.ToString() != "hello, world" {
-		t.Fatalf("read '%s' from (read)", out )
+		t.Fatalf("read '%s' from (read)", out)
 	}
 
 	// Run it again - this time reading will fail
 	out = l.Evaluate(ev)
 
-	if !strings.Contains(out.ToString(), "failed to read from STDIN" ) {
-		t.Fatalf("(read) didn't give expected error, got '%s'", out )
+	if !strings.Contains(out.ToString(), "failed to read from STDIN") {
+		t.Fatalf("(read) didn't give expected error, got '%s'", out)
 	}
 
 }

eval/specials.go

@@ -5,11 +5,11 @@ package eval
 import (
 	"bufio"
 	"fmt"
-	"strings"
-	"sort"
-
 	"github.com/skx/yal/env"
 	"github.com/skx/yal/primitive"
+	"os"
+	"sort"
+	"strings"
 )
 
 // evalSpecialForm is invoked to execute one of our special forms.
@@ -148,6 +148,36 @@ func (ev *Eval) evalSpecialForm(name string, args []primitive.Primitive, e *env.
 			return primitive.Error(fmt.Sprintf("unexpected type for eval %V.", args[0])), true
 		}
 
+	case "exit":
+		ret := 0
+
+		if len(args) == 1 {
+
+			n, ok := args[0].(primitive.Number)
+			if ok {
+				ret = int(n)
+			}
+		}
+
+		os.Exit(ret)
+
+		// not reached
+		return nil, true
+
+	case "forever":
+
+		// We run the body forever.
+		for true {
+
+			// Process all the expressions
+			for _, x := range args {
+				_ = ev.eval(x, e, expandMacro)
+			}
+		}
+
+		// not reached
+		return nil, true
+
 	case "if":
 		if len(args) < 2 {
 			return primitive.ArityError(), true
@@ -237,10 +267,10 @@ func (ev *Eval) evalSpecialForm(name string, args []primitive.Primitive, e *env.
 		proc.Args = arguments
 		proc.Body = body
 		proc.Env = e
-		proc.Help= help
+		proc.Help = help
 		proc.Macro = false
 
-		return proc,true
+		return proc, true
 
 	case "let*":
 		// We need to have at least one argument.
@@ -399,7 +429,7 @@ func (ev *Eval) evalSpecialForm(name string, args []primitive.Primitive, e *env.
 		for _, entry := range ev.stdlib {
 			ret = append(ret, primitive.String(entry))
 		}
-		return ret,true
+		return ret, true
 
 	case "struct":
 		if len(args) <= 1 {