From 0520386674c7d2aaa87f032e52bbb4e3dafb72bd Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Tue, 21 Oct 2014 00:06:49 -0400
Subject: [PATCH] wrote a shitty eval

---
 eval/eval.go            | 77 +++++++++++++++++++++++++++++++++++++++++
 eval/eval_test.go       | 50 ++++++++++++++++++++++++++
 macros/pkgctx/pkgctx.go |  4 +--
 3 files changed, 129 insertions(+), 2 deletions(-)
 create mode 100644 eval/eval.go
 create mode 100644 eval/eval_test.go

diff --git a/eval/eval.go b/eval/eval.go
new file mode 100644
index 0000000..95459a6
--- /dev/null
+++ b/eval/eval.go
@@ -0,0 +1,77 @@
+// The eval package encompasses all that is necesary to do runtime evaluation of
+// ginger structures. These are different than macros in that they aren't turned
+// into go code, instead the compiled go code evaluates them at runtime
+package eval
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"github.com/mediocregopher/ginger/macros/pkgctx"
+	"github.com/mediocregopher/ginger/seq"
+	"github.com/mediocregopher/ginger/types"
+)
+
+// Evaler is a function which can be used inside of eval. It must take in its
+// arguments as a sequence of Elems, and return a resulting Elem
+type Evaler func(seq.Seq) types.Elem
+
+// Bail stops compilation. The given element should be the reason compilation
+// has stopped
+func Bail(el types.Elem, reason string) {
+	fmt.Fprintln(os.Stderr, reason)
+	time.Sleep(100 * time.Second)
+	os.Exit(1)
+}
+
+// Bailf is like Bail, but takes in formatting
+func Bailf(el types.Elem, format string, args ...interface{}) {
+	reason := fmt.Sprintf(format, args...)
+	Bail(el, reason)
+}
+
+var colon = types.GoType{":"}
+
+// Eval takes in the pkgctx it is being executed in, as well as a single Elem to
+// be evaluated, and returns the Elem it evaluates to
+func Eval(p *pkgctx.PkgCtx, el types.Elem) types.Elem {
+	l, ok := el.(*seq.List)
+	if !ok {
+		return el
+	}
+
+	first, rest, ok := l.FirstRest()
+	if !ok || !first.Equal(colon) {
+		return el
+	}
+	
+	fnEl, args, ok := rest.FirstRest()
+	if !ok {
+		Bail(el, "Empty list after colon, no function given")
+	}
+	
+
+	var fnName string
+	if gt, ok := fnEl.(types.GoType); ok {
+		fnName, _ = gt.V.(string)
+	}
+
+	if fnName == "" || fnName[0] != ':' {
+		Bail(el, "Must give a function reference to execute")
+	}
+	fnName = fnName[1:]
+
+	fn, ok := p.CallMap[fnName]
+	if !ok {
+		Bailf(el, "Unknown function name %q", fnName)
+	}
+
+	evalArgFn := func(el types.Elem) types.Elem {
+		return Eval(p, el)
+	}
+
+	evaldArgs := seq.Map(evalArgFn, args)
+
+	return fn.(Evaler)(evaldArgs)
+}
diff --git a/eval/eval_test.go b/eval/eval_test.go
new file mode 100644
index 0000000..7888689
--- /dev/null
+++ b/eval/eval_test.go
@@ -0,0 +1,50 @@
+package eval
+
+import (
+	. "testing"
+
+	"github.com/mediocregopher/ginger/macros/pkgctx"
+	"github.com/mediocregopher/ginger/parse"
+	"github.com/mediocregopher/ginger/seq"
+	"github.com/mediocregopher/ginger/types"
+)
+
+// This is NOT how I want eval to really work in the end, but I wanted to get
+// something down before I kept thinking about it, so I would know what would
+// work
+
+func shittyPlus(s seq.Seq) types.Elem {
+	fn := func(acc, el types.Elem) (types.Elem, bool) {
+		i := acc.(types.GoType).V.(int) + el.(types.GoType).V.(int)
+		return types.GoType{i}, false
+	}
+
+	return seq.Reduce(fn, types.GoType{0}, s)
+}
+
+func TestShittyPlus(t *T) {
+	p := &pkgctx.PkgCtx{
+		CallMap: map[string]interface{}{
+			"shittyPlus": Evaler(shittyPlus),
+		},
+	}
+
+	m := map[string]types.Elem{
+		"(: shittyPlus)":       types.GoType{0},
+		"(: shittyPlus 1 2 3)": types.GoType{6},
+		`(: shittyPlus 1 2 3
+			(: shittyPlus 1 2 3))`: types.GoType{12},
+	}
+
+	for input, output := range m {
+		parsed, err := parse.ParseString(input)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		evald := Eval(p, parsed)
+		if !evald.Equal(output) {
+			t.Fatalf("input: %q %#v != %#v", input, output, evald)
+		}
+	}
+}
diff --git a/macros/pkgctx/pkgctx.go b/macros/pkgctx/pkgctx.go
index 5f1bcde..65c828e 100644
--- a/macros/pkgctx/pkgctx.go
+++ b/macros/pkgctx/pkgctx.go
@@ -9,10 +9,10 @@ type PkgCtx struct {
 	// string for no alias)
 	Packages map[string]string
 
-	// CallDict is a map used by Eval for making actual calls dynamically. The
+	// CallMap is a map used by Eval for making actual calls dynamically. The
 	// key is the string representation of the call to be used (for example,
 	// "fmt.Println") and must agree with the aliases being used in Packages.
 	// The value need not be set during actual compilation, but it is useful to
 	// use it during testing
-	CallDict map[string]interface{}
+	CallMap map[string]interface{}
 }