From 2b9322624f7d58627bcaee521b8d756787bf28d8 Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Sat, 20 Oct 2012 17:43:00 -0400
Subject: [PATCH] added division, prevent div by zero panics

---
 acc.go   | 26 ++++++++++++++++++--------
 proc.go  | 47 +++++++++++++++++++++++++++++++++++------------
 skeam.go |  1 +
 3 files changed, 54 insertions(+), 20 deletions(-)

diff --git a/acc.go b/acc.go
index e6b41d6..be4fb44 100644
--- a/acc.go
+++ b/acc.go
@@ -7,8 +7,8 @@ import (
 
 type accumulator struct {
 	name     string
-	floatFn  func(float64, float64) float64
-	intFn    func(int64, int64) int64
+	floatFn  func(float64, float64) (float64, error)
+	intFn    func(int64, int64) (int64, error)
 	acc      int64
 	accf     float64
 	floating bool
@@ -40,21 +40,31 @@ func (a *accumulator) total(vals ...interface{}) (interface{}, error) {
 	for _, raw := range vals[1:] {
 		switch v := raw.(type) {
 		case int64:
+			var err error
 			if a.floating {
-				a.accf = a.floatFn(a.accf, float64(v))
-				break
+				a.accf, err = a.floatFn(a.accf, float64(v))
+			} else {
+				a.acc, err = a.intFn(a.acc, v)
+			}
+			if err != nil {
+				return nil, err
 			}
-			a.acc = a.intFn(a.acc, v)
 		case float64:
-			if !a.floating {
+			var err error
+			if a.floating {
+				a.accf, err = a.floatFn(a.accf, v)
+			} else {
 				a.floating = true
-				a.accf = a.floatFn(a.accf, float64(a.acc))
+				a.accf, err = a.floatFn(a.accf, float64(a.acc))
+			}
+			if err != nil {
+				return nil, err
 			}
-			a.accf = a.floatFn(a.accf, v)
 		default:
 			return nil, fmt.Errorf("%v is not defined for %v", a.name, reflect.TypeOf(v))
 		}
 	}
+
 	if a.floating {
 		return a.accf, nil
 	} else {
diff --git a/proc.go b/proc.go
index 6d67290..a2501d9 100644
--- a/proc.go
+++ b/proc.go
@@ -1,15 +1,19 @@
 package main
 
+import (
+	"errors"
+)
+
 type proc func(...interface{}) (interface{}, error)
 
 func addition(vals ...interface{}) (interface{}, error) {
 	a := accumulator{
 		name: "addition",
-		floatFn: func(left, right float64) float64 {
-			return left + right
+		floatFn: func(left, right float64) (float64, error) {
+			return left + right, nil
 		},
-		intFn: func(left, right int64) int64 {
-			return left + right
+		intFn: func(left, right int64) (int64, error) {
+			return left + right, nil
 		},
 	}
 	return a.total(vals...)
@@ -18,11 +22,11 @@ func addition(vals ...interface{}) (interface{}, error) {
 func subtraction(vals ...interface{}) (interface{}, error) {
 	a := accumulator{
 		name: "subtraction",
-		floatFn: func(left, right float64) float64 {
-			return left - right
+		floatFn: func(left, right float64) (float64, error) {
+			return left - right, nil
 		},
-		intFn: func(left, right int64) int64 {
-			return left - right
+		intFn: func(left, right int64) (int64, error) {
+			return left - right, nil
 		},
 	}
 	return a.total(vals...)
@@ -31,11 +35,30 @@ func subtraction(vals ...interface{}) (interface{}, error) {
 func multiplication(vals ...interface{}) (interface{}, error) {
 	a := accumulator{
 		name: "multiplication",
-		floatFn: func(left, right float64) float64 {
-			return left * right
+		floatFn: func(left, right float64) (float64, error) {
+			return left * right, nil
+		},
+		intFn: func(left, right int64) (int64, error) {
+			return left * right, nil
+		},
+	}
+	return a.total(vals...)
+}
+
+func division(vals ...interface{}) (interface{}, error) {
+	a := accumulator{
+		name: "division",
+		floatFn: func(left, right float64) (float64, error) {
+			if right == 0.0 {
+				return 0.0, errors.New("float division by zero")
+			}
+			return left / right, nil
 		},
-		intFn: func(left, right int64) int64 {
-			return left * right
+		intFn: func(left, right int64) (int64, error) {
+			if right == 0 {
+				return 0, errors.New("int division by zero")
+			}
+			return left / right, nil
 		},
 	}
 	return a.total(vals...)
diff --git a/skeam.go b/skeam.go
index a3708b9..4600ff1 100644
--- a/skeam.go
+++ b/skeam.go
@@ -23,6 +23,7 @@ var universe = environment{
 	"+":      proc(addition),
 	"-":      proc(subtraction),
 	"*":      proc(multiplication),
+	"/":      proc(division),
 }
 
 // parses the string lexeme into a value that can be eval'd