exp/eval: Converted from bignum to big

Also in this CL:
* Removed util.go, as its functionality is in big
* Removed some semicolons from the code generated by gen.go
* Added a generate target to Makefile
* Removed an outdated TODO from value.go

R=gri
CC=golang-dev
https://golang.org/cl/1780042

10 files changed, 241 insertions, 252 deletions

diff --git a/src/pkg/exp/eval/Makefile b/src/pkg/exp/eval/Makefile
index eac844f1ed..4accbb26da 100644
--- a/src/pkg/exp/eval/Makefile
+++ b/src/pkg/exp/eval/Makefile
@@ -16,7 +16,6 @@ GOFILES=\
 	stmt.go\
 	type.go\
 	typec.go\
-	util.go\
 	value.go\
 	world.go\
 
@@ -27,3 +26,12 @@ main.$O: main.go $(pkgdir)/$(TARG).a
 
 eval: main.$O
 	$(QUOTED_GOBIN)/$(LD) -o $@ $<
+
+gen.$O: gen.go
+	$(QUOTED_GOBIN)/$(GC) $<
+
+expr1.go: gen.$O
+	$(QUOTED_GOBIN)/$(LD) -o generate $<;\
+	./generate > expr1.go;\
+	gofmt -w expr1.go
+
diff --git a/src/pkg/exp/eval/eval_test.go b/src/pkg/exp/eval/eval_test.go
index 1dfdfe1fd6..cd4bbbbb0a 100644
--- a/src/pkg/exp/eval/eval_test.go
+++ b/src/pkg/exp/eval/eval_test.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"flag"
 	"fmt"
 	"log"
@@ -166,12 +166,12 @@ func toValue(val interface{}) Value {
 	case int:
 		r := intV(val)
 		return &r
-	case *bignum.Integer:
+	case *big.Int:
 		return &idealIntV{val}
 	case float:
 		r := floatV(val)
 		return &r
-	case *bignum.Rational:
+	case *big.Rat:
 		return &idealFloatV{val}
 	case string:
 		r := stringV(val)
@@ -235,7 +235,7 @@ func newTestWorld() *World {
 
 	def := func(name string, t Type, val interface{}) { w.DefineVar(name, t, toValue(val)) }
 
-	w.DefineConst("c", IdealIntType, toValue(bignum.Int(1)))
+	w.DefineConst("c", IdealIntType, toValue(big.NewInt(1)))
 	def("i", IntType, 1)
 	def("i2", IntType, 2)
 	def("u", UintType, uint(1))
diff --git a/src/pkg/exp/eval/expr.go b/src/pkg/exp/eval/expr.go
index ea8117d065..9d4fdd84b7 100644
--- a/src/pkg/exp/eval/expr.go
+++ b/src/pkg/exp/eval/expr.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"fmt"
 	"go/ast"
 	"go/token"
@@ -15,6 +15,11 @@ import (
 	"os"
 )
 
+var (
+	idealZero = big.NewInt(0)
+	idealOne  = big.NewInt(1)
+)
+
 // An expr is the result of compiling an expression.  It stores the
 // type of the expression and its evaluator function.
 type expr struct {
@@ -85,7 +90,7 @@ func (a *expr) convertTo(t Type) *expr {
 		log.Crashf("attempted to convert from %v, expected ideal", a.t)
 	}
 
-	var rat *bignum.Rational
+	var rat *big.Rat
 
 	// XXX(Spec)  The spec says "It is erroneous".
 	//
@@ -97,12 +102,12 @@ func (a *expr) convertTo(t Type) *expr {
 	case IdealFloatType:
 		rat = a.asIdealFloat()()
 		if t.isInteger() && !rat.IsInt() {
-			a.diag("constant %v truncated to integer", ratToString(rat))
+			a.diag("constant %v truncated to integer", rat.FloatString(6))
 			return nil
 		}
 	case IdealIntType:
 		i := a.asIdealInt()()
-		rat = bignum.MakeRat(i, bignum.Nat(1))
+		rat = new(big.Rat).SetInt(i)
 	default:
 		log.Crashf("unexpected ideal type %v", a.t)
 	}
@@ -110,11 +115,11 @@ func (a *expr) convertTo(t Type) *expr {
 	// Check bounds
 	if t, ok := t.lit().(BoundedType); ok {
 		if rat.Cmp(t.minVal()) < 0 {
-			a.diag("constant %v underflows %v", ratToString(rat), t)
+			a.diag("constant %v underflows %v", rat.FloatString(6), t)
 			return nil
 		}
 		if rat.Cmp(t.maxVal()) > 0 {
-			a.diag("constant %v overflows %v", ratToString(rat), t)
+			a.diag("constant %v overflows %v", rat.FloatString(6), t)
 			return nil
 		}
 	}
@@ -123,25 +128,26 @@ func (a *expr) convertTo(t Type) *expr {
 	res := a.newExpr(t, a.desc)
 	switch t := t.lit().(type) {
 	case *uintType:
-		n, d := rat.Value()
-		f := n.Quo(bignum.MakeInt(false, d))
-		v := f.Abs().Value()
+		n, d := rat.Num(), rat.Denom()
+		f := new(big.Int).Quo(n, d)
+		f = f.Abs(f)
+		v := uint64(f.Int64())
 		res.eval = func(*Thread) uint64 { return v }
 	case *intType:
-		n, d := rat.Value()
-		f := n.Quo(bignum.MakeInt(false, d))
-		v := f.Value()
+		n, d := rat.Num(), rat.Denom()
+		f := new(big.Int).Quo(n, d)
+		v := f.Int64()
 		res.eval = func(*Thread) int64 { return v }
 	case *idealIntType:
-		n, d := rat.Value()
-		f := n.Quo(bignum.MakeInt(false, d))
-		res.eval = func() *bignum.Integer { return f }
+		n, d := rat.Num(), rat.Denom()
+		f := new(big.Int).Quo(n, d)
+		res.eval = func() *big.Int { return f }
 	case *floatType:
-		n, d := rat.Value()
-		v := float64(n.Value()) / float64(d.Value())
+		n, d := rat.Num(), rat.Denom()
+		v := float64(n.Int64()) / float64(d.Int64())
 		res.eval = func(*Thread) float64 { return v }
 	case *idealFloatType:
-		res.eval = func() *bignum.Rational { return rat }
+		res.eval = func() *big.Rat { return rat }
 	default:
 		log.Crashf("cannot convert to type %T", t)
 	}
@@ -158,7 +164,7 @@ func (a *expr) convertToInt(max int64, negErr string, errOp string) *expr {
 	switch a.t.lit().(type) {
 	case *idealIntType:
 		val := a.asIdealInt()()
-		if negErr != "" && val.IsNeg() {
+		if negErr != "" && val.Sign() < 0 {
 			a.diag("negative %s: %s", negErr, val)
 			return nil
 		}
@@ -166,7 +172,7 @@ func (a *expr) convertToInt(max int64, negErr string, errOp string) *expr {
 		if negErr == "slice" {
 			bound++
 		}
-		if max != -1 && val.Cmp(bignum.Int(bound)) >= 0 {
+		if max != -1 && val.Cmp(big.NewInt(bound)) >= 0 {
 			a.diag("index %s exceeds length %d", val, max)
 			return nil
 		}
@@ -735,14 +741,14 @@ func (a *exprInfo) compileGlobalVariable(v *Variable) *expr {
 	return expr
 }
 
-func (a *exprInfo) compileIdealInt(i *bignum.Integer, desc string) *expr {
+func (a *exprInfo) compileIdealInt(i *big.Int, desc string) *expr {
 	expr := a.newExpr(IdealIntType, desc)
-	expr.eval = func() *bignum.Integer { return i }
+	expr.eval = func() *big.Int { return i }
 	return expr
 }
 
 func (a *exprInfo) compileIntLit(lit string) *expr {
-	i, _, _ := bignum.IntFromString(lit, 0)
+	i, _ := new(big.Int).SetString(lit, 0)
 	return a.compileIdealInt(i, "integer literal")
 }
 
@@ -758,16 +764,16 @@ func (a *exprInfo) compileCharLit(lit string) *expr {
 		a.silentErrors++
 		return nil
 	}
-	return a.compileIdealInt(bignum.Int(int64(v)), "character literal")
+	return a.compileIdealInt(big.NewInt(int64(v)), "character literal")
 }
 
 func (a *exprInfo) compileFloatLit(lit string) *expr {
-	f, _, n := bignum.RatFromString(lit, 10)
-	if n != len(lit) {
+	f, ok := new(big.Rat).SetString(lit)
+	if !ok {
 		log.Crashf("malformed float literal %s at %v passed parser", lit, a.pos)
 	}
 	expr := a.newExpr(IdealFloatType, "float literal")
-	expr.eval = func() *bignum.Rational { return f }
+	expr.eval = func() *big.Rat { return f }
 	return expr
 }
 
@@ -1774,8 +1780,8 @@ func (a *exprInfo) compileBinaryExpr(op token.Token, l, r *expr) *expr {
 	switch op {
 	case token.QUO, token.REM:
 		if r.t.isIdeal() {
-			if (r.t.isInteger() && r.asIdealInt()().IsZero()) ||
-				(r.t.isFloat() && r.asIdealFloat()().IsZero()) {
+			if (r.t.isInteger() && r.asIdealInt()().Sign() == 0) ||
+				(r.t.isFloat() && r.asIdealFloat()().Sign() == 0) {
 				a.diag("divide by zero")
 				return nil
 			}
@@ -1817,13 +1823,13 @@ func (a *exprInfo) compileBinaryExpr(op token.Token, l, r *expr) *expr {
 			lv := l.asIdealInt()()
 			rv := r.asIdealInt()()
 			const maxShift = 99999
-			if rv.Cmp(bignum.Int(maxShift)) > 0 {
+			if rv.Cmp(big.NewInt(maxShift)) > 0 {
 				a.diag("left shift by %v; exceeds implementation limit of %v", rv, maxShift)
 				expr.t = nil
 				return nil
 			}
-			val := lv.Shl(uint(rv.Value()))
-			expr.eval = func() *bignum.Integer { return val }
+			val := new(big.Int).Lsh(lv, uint(rv.Int64()))
+			expr.eval = func() *big.Int { return val }
 		} else {
 			expr.genBinOpShl(l, r)
 		}
@@ -1832,8 +1838,8 @@ func (a *exprInfo) compileBinaryExpr(op token.Token, l, r *expr) *expr {
 		if l.t.isIdeal() {
 			lv := l.asIdealInt()()
 			rv := r.asIdealInt()()
-			val := lv.Shr(uint(rv.Value()))
-			expr.eval = func() *bignum.Integer { return val }
+			val := new(big.Int).Rsh(lv, uint(rv.Int64()))
+			expr.eval = func() *big.Int { return val }
 		} else {
 			expr.genBinOpShr(l, r)
 		}
diff --git a/src/pkg/exp/eval/expr1.go b/src/pkg/exp/eval/expr1.go
index f0a78ac4d6..81bc3a2202 100644..100755
--- a/src/pkg/exp/eval/expr1.go
+++ b/src/pkg/exp/eval/expr1.go
@@ -4,13 +4,13 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"log"
 )
 
 /*
- * "As" functions.  These retrieve evaluator functions from an
- * expr, panicking if the requested evaluator has the wrong type.
+* "As" functions.  These retrieve evaluator functions from an
+* expr, panicking if the requested evaluator has the wrong type.
  */
 func (a *expr) asBool() func(*Thread) bool {
 	return a.eval.(func(*Thread) bool)
@@ -21,14 +21,14 @@ func (a *expr) asUint() func(*Thread) uint64 {
 func (a *expr) asInt() func(*Thread) int64 {
 	return a.eval.(func(*Thread) int64)
 }
-func (a *expr) asIdealInt() func() *bignum.Integer {
-	return a.eval.(func() *bignum.Integer)
+func (a *expr) asIdealInt() func() *big.Int {
+	return a.eval.(func() *big.Int)
 }
 func (a *expr) asFloat() func(*Thread) float64 {
 	return a.eval.(func(*Thread) float64)
 }
-func (a *expr) asIdealFloat() func() *bignum.Rational {
-	return a.eval.(func() *bignum.Rational)
+func (a *expr) asIdealFloat() func() *big.Rat {
+	return a.eval.(func() *big.Rat)
 }
 func (a *expr) asString() func(*Thread) string {
 	return a.eval.(func(*Thread) string)
@@ -63,11 +63,11 @@ func (a *expr) asInterface() func(*Thread) interface{} {
 		return func(t *Thread) interface{} { return sf(t) }
 	case func(t *Thread) int64:
 		return func(t *Thread) interface{} { return sf(t) }
-	case func() *bignum.Integer:
+	case func() *big.Int:
 		return func(*Thread) interface{} { return sf() }
 	case func(t *Thread) float64:
 		return func(t *Thread) interface{} { return sf(t) }
-	case func() *bignum.Rational:
+	case func() *big.Rat:
 		return func(*Thread) interface{} { return sf() }
 	case func(t *Thread) string:
 		return func(t *Thread) interface{} { return sf(t) }
@@ -90,7 +90,7 @@ func (a *expr) asInterface() func(*Thread) interface{} {
 }
 
 /*
- * Operator generators.
+* Operator generators.
  */
 
 func (a *expr) genConstant(v Value) {
@@ -103,12 +103,12 @@ func (a *expr) genConstant(v Value) {
 		a.eval = func(t *Thread) int64 { return v.(IntValue).Get(t) }
 	case *idealIntType:
 		val := v.(IdealIntValue).Get()
-		a.eval = func() *bignum.Integer { return val }
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		a.eval = func(t *Thread) float64 { return v.(FloatValue).Get(t) }
 	case *idealFloatType:
 		val := v.(IdealFloatValue).Get()
-		a.eval = func() *bignum.Rational { return val }
+		a.eval = func() *big.Rat { return val }
 	case *stringType:
 		a.eval = func(t *Thread) string { return v.(StringValue).Get(t) }
 	case *ArrayType:
@@ -229,16 +229,16 @@ func (a *expr) genUnaryOpNeg(v *expr) {
 		vf := v.asInt()
 		a.eval = func(t *Thread) int64 { v := vf(t); return -v }
 	case *idealIntType:
-		v := v.asIdealInt()()
-		val := v.Neg()
-		a.eval = func() *bignum.Integer { return val }
+		val := v.asIdealInt()()
+		val.Neg(val)
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		vf := v.asFloat()
 		a.eval = func(t *Thread) float64 { v := vf(t); return -v }
 	case *idealFloatType:
-		v := v.asIdealFloat()()
-		val := v.Neg()
-		a.eval = func() *bignum.Rational { return val }
+		val := v.asIdealFloat()()
+		val.Neg(val)
+		a.eval = func() *big.Rat { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", a.t, a.pos)
 	}
@@ -263,9 +263,9 @@ func (a *expr) genUnaryOpXor(v *expr) {
 		vf := v.asInt()
 		a.eval = func(t *Thread) int64 { v := vf(t); return ^v }
 	case *idealIntType:
-		v := v.asIdealInt()()
-		val := v.Neg().Sub(bignum.Int(1))
-		a.eval = func() *bignum.Integer { return val }
+		val := v.asIdealInt()()
+		val.Not(val)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", a.t, a.pos)
 	}
@@ -372,8 +372,8 @@ func (a *expr) genBinOpAdd(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Add(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Add(l, r)
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		lf := l.asFloat()
 		rf := r.asFloat()
@@ -405,8 +405,8 @@ func (a *expr) genBinOpAdd(l, r *expr) {
 	case *idealFloatType:
 		l := l.asIdealFloat()()
 		r := r.asIdealFloat()()
-		val := l.Add(r)
-		a.eval = func() *bignum.Rational { return val }
+		val := l.Add(l, r)
+		a.eval = func() *big.Rat { return val }
 	case *stringType:
 		lf := l.asString()
 		rf := r.asString()
@@ -508,8 +508,8 @@ func (a *expr) genBinOpSub(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Sub(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Sub(l, r)
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		lf := l.asFloat()
 		rf := r.asFloat()
@@ -541,8 +541,8 @@ func (a *expr) genBinOpSub(l, r *expr) {
 	case *idealFloatType:
 		l := l.asIdealFloat()()
 		r := r.asIdealFloat()()
-		val := l.Sub(r)
-		a.eval = func() *bignum.Rational { return val }
+		val := l.Sub(l, r)
+		a.eval = func() *big.Rat { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -637,8 +637,8 @@ func (a *expr) genBinOpMul(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Mul(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Mul(l, r)
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		lf := l.asFloat()
 		rf := r.asFloat()
@@ -670,8 +670,8 @@ func (a *expr) genBinOpMul(l, r *expr) {
 	case *idealFloatType:
 		l := l.asIdealFloat()()
 		r := r.asIdealFloat()()
-		val := l.Mul(r)
-		a.eval = func() *bignum.Rational { return val }
+		val := l.Mul(l, r)
+		a.eval = func() *big.Rat { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -796,8 +796,8 @@ func (a *expr) genBinOpQuo(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Quo(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Quo(l, r)
+		a.eval = func() *big.Int { return val }
 	case *floatType:
 		lf := l.asFloat()
 		rf := r.asFloat()
@@ -838,8 +838,8 @@ func (a *expr) genBinOpQuo(l, r *expr) {
 	case *idealFloatType:
 		l := l.asIdealFloat()()
 		r := r.asIdealFloat()()
-		val := l.Quo(r)
-		a.eval = func() *bignum.Rational { return val }
+		val := l.Quo(l, r)
+		a.eval = func() *big.Rat { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -964,8 +964,8 @@ func (a *expr) genBinOpRem(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Rem(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Rem(l, r)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -1060,8 +1060,8 @@ func (a *expr) genBinOpAnd(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.And(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.And(l, r)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -1156,8 +1156,8 @@ func (a *expr) genBinOpOr(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Or(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Or(l, r)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -1252,8 +1252,8 @@ func (a *expr) genBinOpXor(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.Xor(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.Xor(l, r)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
@@ -1348,8 +1348,8 @@ func (a *expr) genBinOpAndNot(l, r *expr) {
 	case *idealIntType:
 		l := l.asIdealInt()()
 		r := r.asIdealInt()()
-		val := l.AndNot(r)
-		a.eval = func() *bignum.Integer { return val }
+		val := l.AndNot(l, r)
+		a.eval = func() *big.Int { return val }
 	default:
 		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
diff --git a/src/pkg/exp/eval/expr_test.go b/src/pkg/exp/eval/expr_test.go
index b36554183e..0dbce43152 100644
--- a/src/pkg/exp/eval/expr_test.go
+++ b/src/pkg/exp/eval/expr_test.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"testing"
 )
 
@@ -22,7 +22,7 @@ var implLimit = "implementation limit"
 var mustBeUnsigned = "must be unsigned"
 var divByZero = "divide by zero"
 
-var hugeInteger = bignum.Int(1).Shl(64)
+var hugeInteger = new(big.Int).Lsh(idealOne, 64)
 
 var exprTests = []test{
 	Val("i", 1),
@@ -30,9 +30,9 @@ var exprTests = []test{
 	// TODO(austin) Test variable in constant context
 	//CErr("t", typeAsExpr),
 
-	Val("'a'", bignum.Int('a')),
-	Val("'\\uffff'", bignum.Int('\uffff')),
-	Val("'\\n'", bignum.Int('\n')),
+	Val("'a'", big.NewInt('a')),
+	Val("'\\uffff'", big.NewInt('\uffff')),
+	Val("'\\n'", big.NewInt('\n')),
 	CErr("''+x", badCharLit),
 	// Produces two parse errors
 	//CErr("'''", ""),
@@ -40,10 +40,10 @@ var exprTests = []test{
 	CErr("'\\z'", unknownEscape),
 	CErr("'ab'", badCharLit),
 
-	Val("1.0", bignum.Rat(1, 1)),
-	Val("1.", bignum.Rat(1, 1)),
-	Val(".1", bignum.Rat(1, 10)),
-	Val("1e2", bignum.Rat(100, 1)),
+	Val("1.0", big.NewRat(1, 1)),
+	Val("1.", big.NewRat(1, 1)),
+	Val(".1", big.NewRat(1, 10)),
+	Val("1e2", big.NewRat(100, 1)),
 
 	Val("\"abc\"", "abc"),
 	Val("\"\"", ""),
@@ -140,12 +140,12 @@ var exprTests = []test{
 	CErr("&c", badAddrOf),
 	Val("*(&ai[0])", 1),
 
-	Val("+1", bignum.Int(+1)),
-	Val("+1.0", bignum.Rat(1, 1)),
-	Val("01.5", bignum.Rat(15, 10)),
+	Val("+1", big.NewInt(+1)),
+	Val("+1.0", big.NewRat(1, 1)),
+	Val("01.5", big.NewRat(15, 10)),
 	CErr("+\"x\"", opTypes),
 
-	Val("-42", bignum.Int(-42)),
+	Val("-42", big.NewInt(-42)),
 	Val("-i", -1),
 	Val("-f", -1.0),
 	// 6g bug?
@@ -154,8 +154,8 @@ var exprTests = []test{
 
 	// TODO(austin) Test unary !
 
-	Val("^2", bignum.Int(^2)),
-	Val("^(-2)", bignum.Int(^(-2))),
+	Val("^2", big.NewInt(^2)),
+	Val("^(-2)", big.NewInt(^(-2))),
 	CErr("^2.0", opTypes),
 	CErr("^2.5", opTypes),
 	Val("^i", ^1),
@@ -165,67 +165,66 @@ var exprTests = []test{
 	Val("1+i", 2),
 	Val("1+u", uint(2)),
 	Val("3.0+i", 4),
-	Val("1+1", bignum.Int(2)),
+	Val("1+1", big.NewInt(2)),
 	Val("f+f", 2.0),
 	Val("1+f", 2.0),
-	Val("1.0+1", bignum.Rat(2, 1)),
+	Val("1.0+1", big.NewRat(2, 1)),
 	Val("\"abc\" + \"def\"", "abcdef"),
 	CErr("i+u", opTypes),
 	CErr("-1+u", constantUnderflows),
 	// TODO(austin) Test named types
 
-	Val("2-1", bignum.Int(1)),
-	Val("2.0-1", bignum.Rat(1, 1)),
+	Val("2-1", big.NewInt(1)),
+	Val("2.0-1", big.NewRat(1, 1)),
 	Val("f-2", -1.0),
-	// TOOD(austin) bignum can't do negative 0?
-	//Val("-0.0", XXX),
-	Val("2*2", bignum.Int(4)),
+	Val("-0.0", big.NewRat(0, 1)),
+	Val("2*2", big.NewInt(4)),
 	Val("2*i", 2),
-	Val("3/2", bignum.Int(1)),
+	Val("3/2", big.NewInt(1)),
 	Val("3/i", 3),
 	CErr("1/0", divByZero),
 	CErr("1.0/0", divByZero),
 	RErr("i/0", divByZero),
-	Val("3%2", bignum.Int(1)),
+	Val("3%2", big.NewInt(1)),
 	Val("i%2", 1),
 	CErr("3%0", divByZero),
 	CErr("3.0%0", opTypes),
 	RErr("i%0", divByZero),
 
 	// Examples from "Arithmetic operators"
-	Val("5/3", bignum.Int(1)),
+	Val("5/3", big.NewInt(1)),
 	Val("(i+4)/(i+2)", 1),
-	Val("5%3", bignum.Int(2)),
+	Val("5%3", big.NewInt(2)),
 	Val("(i+4)%(i+2)", 2),
-	Val("-5/3", bignum.Int(-1)),
+	Val("-5/3", big.NewInt(-1)),
 	Val("(i-6)/(i+2)", -1),
-	Val("-5%3", bignum.Int(-2)),
+	Val("-5%3", big.NewInt(-2)),
 	Val("(i-6)%(i+2)", -2),
-	Val("5/-3", bignum.Int(-1)),
+	Val("5/-3", big.NewInt(-1)),
 	Val("(i+4)/(i-4)", -1),
-	Val("5%-3", bignum.Int(2)),
+	Val("5%-3", big.NewInt(2)),
 	Val("(i+4)%(i-4)", 2),
-	Val("-5/-3", bignum.Int(1)),
+	Val("-5/-3", big.NewInt(1)),
 	Val("(i-6)/(i-4)", 1),
-	Val("-5%-3", bignum.Int(-2)),
+	Val("-5%-3", big.NewInt(-2)),
 	Val("(i-6)%(i-4)", -2),
 
 	// Examples from "Arithmetic operators"
-	Val("11/4", bignum.Int(2)),
+	Val("11/4", big.NewInt(2)),
 	Val("(i+10)/4", 2),
-	Val("11%4", bignum.Int(3)),
+	Val("11%4", big.NewInt(3)),
 	Val("(i+10)%4", 3),
-	Val("11>>2", bignum.Int(2)),
+	Val("11>>2", big.NewInt(2)),
 	Val("(i+10)>>2", 2),
-	Val("11&3", bignum.Int(3)),
+	Val("11&3", big.NewInt(3)),
 	Val("(i+10)&3", 3),
-	Val("-11/4", bignum.Int(-2)),
+	Val("-11/4", big.NewInt(-2)),
 	Val("(i-12)/4", -2),
-	Val("-11%4", bignum.Int(-3)),
+	Val("-11%4", big.NewInt(-3)),
 	Val("(i-12)%4", -3),
-	Val("-11>>2", bignum.Int(-3)),
+	Val("-11>>2", big.NewInt(-3)),
 	Val("(i-12)>>2", -3),
-	Val("-11&3", bignum.Int(1)),
+	Val("-11&3", big.NewInt(1)),
 	Val("(i-12)&3", 1),
 
 	// TODO(austin) Test bit ops
@@ -234,29 +233,29 @@ var exprTests = []test{
 	// ideal int, negative ideal int, big ideal int, ideal
 	// fractional float, ideal non-fractional float, int, uint,
 	// and float.
-	Val("2<<2", bignum.Int(2<<2)),
+	Val("2<<2", big.NewInt(2<<2)),
 	CErr("2<<(-1)", constantUnderflows),
 	CErr("2<<0x10000000000000000", constantOverflows),
 	CErr("2<<2.5", constantTruncated),
-	Val("2<<2.0", bignum.Int(2<<2.0)),
+	Val("2<<2.0", big.NewInt(2<<2.0)),
 	CErr("2<<i", mustBeUnsigned),
 	Val("2<<u", 2<<1),
 	CErr("2<<f", opTypes),
 
-	Val("-2<<2", bignum.Int(-2<<2)),
+	Val("-2<<2", big.NewInt(-2<<2)),
 	CErr("-2<<(-1)", constantUnderflows),
 	CErr("-2<<0x10000000000000000", constantOverflows),
 	CErr("-2<<2.5", constantTruncated),
-	Val("-2<<2.0", bignum.Int(-2<<2.0)),
+	Val("-2<<2.0", big.NewInt(-2<<2.0)),
 	CErr("-2<<i", mustBeUnsigned),
 	Val("-2<<u", -2<<1),
 	CErr("-2<<f", opTypes),
 
-	Val("0x10000000000000000<<2", hugeInteger.Shl(2)),
+	Val("0x10000000000000000<<2", new(big.Int).Lsh(hugeInteger, 2)),
 	CErr("0x10000000000000000<<(-1)", constantUnderflows),
 	CErr("0x10000000000000000<<0x10000000000000000", constantOverflows),
 	CErr("0x10000000000000000<<2.5", constantTruncated),
-	Val("0x10000000000000000<<2.0", hugeInteger.Shl(2)),
+	Val("0x10000000000000000<<2.0", new(big.Int).Lsh(hugeInteger, 2)),
 	CErr("0x10000000000000000<<i", mustBeUnsigned),
 	CErr("0x10000000000000000<<u", constantOverflows),
 	CErr("0x10000000000000000<<f", opTypes),
diff --git a/src/pkg/exp/eval/gen.go b/src/pkg/exp/eval/gen.go
index 969d655862..80179c89aa 100644
--- a/src/pkg/exp/eval/gen.go
+++ b/src/pkg/exp/eval/gen.go
@@ -45,11 +45,11 @@ var (
 	intType = &Type{Repr: "*intType", Value: "IntValue", Native: "int64", As: "asInt",
 		Sizes: []Size{Size{8, "int8"}, Size{16, "int16"}, Size{32, "int32"}, Size{64, "int64"}, Size{0, "int"}},
 	}
-	idealIntType = &Type{Repr: "*idealIntType", Value: "IdealIntValue", Native: "*bignum.Integer", As: "asIdealInt", IsIdeal: true}
+	idealIntType = &Type{Repr: "*idealIntType", Value: "IdealIntValue", Native: "*big.Int", As: "asIdealInt", IsIdeal: true}
 	floatType    = &Type{Repr: "*floatType", Value: "FloatValue", Native: "float64", As: "asFloat",
 		Sizes: []Size{Size{32, "float32"}, Size{64, "float64"}, Size{0, "float"}},
 	}
-	idealFloatType = &Type{Repr: "*idealFloatType", Value: "IdealFloatValue", Native: "*bignum.Rational", As: "asIdealFloat", IsIdeal: true}
+	idealFloatType = &Type{Repr: "*idealFloatType", Value: "IdealFloatValue", Native: "*big.Rat", As: "asIdealFloat", IsIdeal: true}
 	stringType     = &Type{Repr: "*stringType", Value: "StringValue", Native: "string", As: "asString"}
 	arrayType      = &Type{Repr: "*ArrayType", Value: "ArrayValue", Native: "ArrayValue", As: "asArray", HasAssign: true}
 	structType     = &Type{Repr: "*StructType", Value: "StructValue", Native: "StructValue", As: "asStruct", HasAssign: true}
@@ -93,33 +93,33 @@ var (
 )
 
 var unOps = []Op{
-	Op{Name: "Neg", Expr: "-v", ConstExpr: "v.Neg()", Types: numbers},
+	Op{Name: "Neg", Expr: "-v", ConstExpr: "val.Neg(val)", Types: numbers},
 	Op{Name: "Not", Expr: "!v", Types: bools},
-	Op{Name: "Xor", Expr: "^v", ConstExpr: "v.Neg().Sub(bignum.Int(1))", Types: integers},
+	Op{Name: "Xor", Expr: "^v", ConstExpr: "val.Not(val)", Types: integers},
 }
 
 var binOps = []Op{
-	Op{Name: "Add", Expr: "l + r", ConstExpr: "l.Add(r)", Types: addable},
-	Op{Name: "Sub", Expr: "l - r", ConstExpr: "l.Sub(r)", Types: numbers},
-	Op{Name: "Mul", Expr: "l * r", ConstExpr: "l.Mul(r)", Types: numbers},
+	Op{Name: "Add", Expr: "l + r", ConstExpr: "l.Add(l, r)", Types: addable},
+	Op{Name: "Sub", Expr: "l - r", ConstExpr: "l.Sub(l, r)", Types: numbers},
+	Op{Name: "Mul", Expr: "l * r", ConstExpr: "l.Mul(l, r)", Types: numbers},
 	Op{Name: "Quo",
 		Body:      "if r == 0 { t.Abort(DivByZeroError{}) }; ret =  l / r",
-		ConstExpr: "l.Quo(r)",
+		ConstExpr: "l.Quo(l, r)",
 		Types:     numbers,
 	},
 	Op{Name: "Rem",
 		Body:      "if r == 0 { t.Abort(DivByZeroError{}) }; ret = l % r",
-		ConstExpr: "l.Rem(r)",
+		ConstExpr: "l.Rem(l, r)",
 		Types:     integers,
 	},
-	Op{Name: "And", Expr: "l & r", ConstExpr: "l.And(r)", Types: integers},
-	Op{Name: "Or", Expr: "l | r", ConstExpr: "l.Or(r)", Types: integers},
-	Op{Name: "Xor", Expr: "l ^ r", ConstExpr: "l.Xor(r)", Types: integers},
-	Op{Name: "AndNot", Expr: "l &^ r", ConstExpr: "l.AndNot(r)", Types: integers},
-	Op{Name: "Shl", Expr: "l << r", ConstExpr: "l.Shl(uint(r.Value()))",
+	Op{Name: "And", Expr: "l & r", ConstExpr: "l.And(l, r)", Types: integers},
+	Op{Name: "Or", Expr: "l | r", ConstExpr: "l.Or(l, r)", Types: integers},
+	Op{Name: "Xor", Expr: "l ^ r", ConstExpr: "l.Xor(l, r)", Types: integers},
+	Op{Name: "AndNot", Expr: "l &^ r", ConstExpr: "l.AndNot(l, r)", Types: integers},
+	Op{Name: "Shl", Expr: "l << r", ConstExpr: "l.Lsh(l, uint(r.Value()))",
 		AsRightName: "asUint", Types: shiftable,
 	},
-	Op{Name: "Shr", Expr: "l >> r", ConstExpr: "l.Shr(uint(r.Value()))",
+	Op{Name: "Shr", Expr: "l >> r", ConstExpr: "new(big.Int).Rsh(l, uint(r.Value()))",
 		AsRightName: "asUint", Types: shiftable,
 	},
 	Op{Name: "Lss", Expr: "l < r", ConstExpr: "l.Cmp(r) < 0", ReturnType: "bool", Types: addable},
@@ -149,8 +149,8 @@ const templateStr = `
 package eval
 
 import (
-	"bignum";
-	"log";
+	"big"
+	"log"
 )
 
 /*
@@ -184,9 +184,9 @@ func (a *expr) asInterface() (func(*Thread) interface{}) {
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected expression node type %T at %v", a.eval, a.pos);
+		log.Crashf("unexpected expression node type %T at %v", a.eval, a.pos)
 	}
-	panic("fail");
+	panic("fail")
 }
 
 /*
@@ -198,19 +198,19 @@ func (a *expr) genConstant(v Value) {
 «.repeated section Types»
 	case «Repr»:
 «.section IsIdeal»
-		val := v.(«Value»).Get();
+		val := v.(«Value»).Get()
 		a.eval = func() «Native» { return val }
 «.or»
 		a.eval = func(t *Thread) «Native» { return v.(«Value»).Get(t) }
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected constant type %v at %v", a.t, a.pos);
+		log.Crashf("unexpected constant type %v at %v", a.t, a.pos)
 	}
 }
 
 func (a *expr) genIdentOp(level, index int) {
-	a.evalAddr = func(t *Thread) Value { return t.f.Get(level, index) };
+	a.evalAddr = func(t *Thread) Value { return t.f.Get(level, index) }
 	switch a.t.lit().(type) {
 «.repeated section Types»
 «.section IsIdeal»
@@ -220,12 +220,12 @@ func (a *expr) genIdentOp(level, index int) {
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected identifier type %v at %v", a.t, a.pos);
+		log.Crashf("unexpected identifier type %v at %v", a.t, a.pos)
 	}
 }
 
 func (a *expr) genFuncCall(call func(t *Thread) []Value) {
-	a.exec = func(t *Thread) { call(t)};
+	a.exec = func(t *Thread) { call(t)}
 	switch a.t.lit().(type) {
 «.repeated section Types»
 «.section IsIdeal»
@@ -237,12 +237,12 @@ func (a *expr) genFuncCall(call func(t *Thread) []Value) {
 	case *MultiType:
 		a.eval = func(t *Thread) []Value { return call(t) }
 	default:
-		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos)
 	}
 }
 
 func (a *expr) genValue(vf func(*Thread) Value) {
-	a.evalAddr = vf;
+	a.evalAddr = vf
 	switch a.t.lit().(type) {
 «.repeated section Types»
 «.section IsIdeal»
@@ -252,7 +252,7 @@ func (a *expr) genValue(vf func(*Thread) Value) {
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected result type %v at %v", a.t, a.pos);
+		log.Crashf("unexpected result type %v at %v", a.t, a.pos)
 	}
 }
 
@@ -262,29 +262,29 @@ func (a *expr) genUnaryOp«Name»(v *expr) {
 «.repeated section Types»
 	case «Repr»:
 «.section IsIdeal»
-		v := v.«As»()();
-		val := «ConstExpr»;
+		val := v.«As»()()
+		«ConstExpr»
 		a.eval = func() «Native» { return val }
 «.or»
-		vf := v.«As»();
+		vf := v.«As»()
 		a.eval = func(t *Thread) «Native» { v := vf(t); return «Expr» }
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected type %v at %v", a.t, a.pos);
+		log.Crashf("unexpected type %v at %v", a.t, a.pos)
 	}
 }
 
 «.end»
 func (a *expr) genBinOpLogAnd(l, r *expr) {
-	lf := l.asBool();
-	rf := r.asBool();
+	lf := l.asBool()
+	rf := r.asBool()
 	a.eval = func(t *Thread) bool { return lf(t) && rf(t) }
 }
 
 func (a *expr) genBinOpLogOr(l, r *expr) {
-	lf := l.asBool();
-	rf := r.asBool();
+	lf := l.asBool()
+	rf := r.asBool()
 	a.eval = func(t *Thread) bool { return lf(t) || rf(t) }
 }
 
@@ -294,20 +294,20 @@ func (a *expr) genBinOp«Name»(l, r *expr) {
 «.repeated section Types»
 	case «Repr»:
 	«.section IsIdeal»
-		l := l.«As»()();
-		r := r.«As»()();
-		val := «ConstExpr»;
+		l := l.«As»()()
+		r := r.«As»()()
+		val := «ConstExpr»
 		«.section ReturnType»
 		a.eval = func(t *Thread) «ReturnType» { return val }
 		«.or»
 		a.eval = func() «Native» { return val }
 		«.end»
 	«.or»
-		lf := l.«As»();
-		rf := r.«.section AsRightName»«@»«.or»«As»«.end»();
+		lf := l.«As»()
+		rf := r.«.section AsRightName»«@»«.or»«As»«.end»()
 		«.section ReturnType»
 		a.eval = func(t *Thread) «@» {
-			l, r := lf(t), rf(t);
+			l, r := lf(t), rf(t)
 			return «Expr»
 		}
 		«.or»
@@ -316,22 +316,22 @@ func (a *expr) genBinOp«Name»(l, r *expr) {
 		«.repeated section @»
 		case «Bits»:
 			a.eval = func(t *Thread) «Native» {
-				l, r := lf(t), rf(t);
-				var ret «Native»;
+				l, r := lf(t), rf(t)
+				var ret «Native»
 				«.section Body»
-				«Body»;
+				«Body»
 				«.or»
-				ret = «Expr»;
+				ret = «Expr»
 				«.end»
 				return «Native»(«Sized»(ret))
 			}
 		«.end»
 		default:
-			log.Crashf("unexpected size %d in type %v at %v", t.Bits, t, a.pos);
+			log.Crashf("unexpected size %d in type %v at %v", t.Bits, t, a.pos)
 		}
 		«.or»
 		a.eval = func(t *Thread) «Native» {
-			l, r := lf(t), rf(t);
+			l, r := lf(t), rf(t)
 			return «Expr»
 		}
 		«.end»
@@ -339,7 +339,7 @@ func (a *expr) genBinOp«Name»(l, r *expr) {
 	«.end»
 	«.end»
 	default:
-		log.Crashf("unexpected type %v at %v", l.t, a.pos);
+		log.Crashf("unexpected type %v at %v", l.t, a.pos)
 	}
 }
 
@@ -350,14 +350,14 @@ func genAssign(lt Type, r *expr) (func(lv Value, t *Thread)) {
 «.section IsIdeal»
 «.or»
 	case «Repr»:
-		rf := r.«As»();
+		rf := r.«As»()
 		return func(lv Value, t *Thread) { «.section HasAssign»lv.Assign(t, rf(t))«.or»lv.(«Value»).Set(t, rf(t))«.end» }
 «.end»
 «.end»
 	default:
-		log.Crashf("unexpected left operand type %v at %v", lt, r.pos);
+		log.Crashf("unexpected left operand type %v at %v", lt, r.pos)
 	}
-	panic("fail");
+	panic("fail")
 }
 `
 
diff --git a/src/pkg/exp/eval/stmt.go b/src/pkg/exp/eval/stmt.go
index bcd81f04cb..24e9515625 100644
--- a/src/pkg/exp/eval/stmt.go
+++ b/src/pkg/exp/eval/stmt.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"log"
 	"go/ast"
 	"go/token"
@@ -493,7 +493,7 @@ func (a *stmtCompiler) compileIncDecStmt(s *ast.IncDecStmt) {
 
 	one := l.newExpr(IdealIntType, "constant")
 	one.pos = s.Pos()
-	one.eval = func() *bignum.Integer { return bignum.Int(1) }
+	one.eval = func() *big.Int { return big.NewInt(1) }
 
 	binop := l.compileBinaryExpr(op, l, one)
 	if binop == nil {
diff --git a/src/pkg/exp/eval/type.go b/src/pkg/exp/eval/type.go
index b0fbe21565..86924494f8 100644
--- a/src/pkg/exp/eval/type.go
+++ b/src/pkg/exp/eval/type.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"go/ast"
 	"go/token"
 	"log"
@@ -60,9 +60,9 @@ type Type interface {
 type BoundedType interface {
 	Type
 	// minVal returns the smallest value of this type.
-	minVal() *bignum.Rational
+	minVal() *big.Rat
 	// maxVal returns the largest value of this type.
-	maxVal() *bignum.Rational
+	maxVal() *big.Rat
 }
 
 var universePos = token.Position{"<universe>", 0, 0, 0}
@@ -234,9 +234,9 @@ func (t *uintType) Zero() Value {
 	panic("unexpected uint bit count")
 }
 
-func (t *uintType) minVal() *bignum.Rational { return bignum.Rat(0, 1) }
+func (t *uintType) minVal() *big.Rat { return big.NewRat(0, 1) }
 
-func (t *uintType) maxVal() *bignum.Rational {
+func (t *uintType) maxVal() *big.Rat {
 	bits := t.Bits
 	if bits == 0 {
 		if t.Ptr {
@@ -245,7 +245,10 @@ func (t *uintType) maxVal() *bignum.Rational {
 			bits = uint(8 * unsafe.Sizeof(uint(0)))
 		}
 	}
-	return bignum.MakeRat(bignum.Int(1).Shl(bits).Add(bignum.Int(-1)), bignum.Nat(1))
+	numer := big.NewInt(1)
+	numer.Lsh(numer, bits)
+	numer.Sub(numer, idealOne)
+	return new(big.Rat).SetInt(numer)
 }
 
 /*
@@ -307,20 +310,25 @@ func (t *intType) Zero() Value {
 	panic("unexpected int bit count")
 }
 
-func (t *intType) minVal() *bignum.Rational {
+func (t *intType) minVal() *big.Rat {
 	bits := t.Bits
 	if bits == 0 {
 		bits = uint(8 * unsafe.Sizeof(int(0)))
 	}
-	return bignum.MakeRat(bignum.Int(-1).Shl(bits-1), bignum.Nat(1))
+	numer := big.NewInt(-1)
+	numer.Lsh(numer, bits-1)
+	return new(big.Rat).SetInt(numer)
 }
 
-func (t *intType) maxVal() *bignum.Rational {
+func (t *intType) maxVal() *big.Rat {
 	bits := t.Bits
 	if bits == 0 {
 		bits = uint(8 * unsafe.Sizeof(int(0)))
 	}
-	return bignum.MakeRat(bignum.Int(1).Shl(bits-1).Add(bignum.Int(-1)), bignum.Nat(1))
+	numer := big.NewInt(1)
+	numer.Lsh(numer, bits-1)
+	numer.Sub(numer, idealOne)
+	return new(big.Rat).SetInt(numer)
 }
 
 /*
@@ -346,7 +354,7 @@ func (t *idealIntType) isIdeal() bool { return true }
 
 func (t *idealIntType) String() string { return "ideal integer" }
 
-func (t *idealIntType) Zero() Value { return &idealIntV{bignum.Int(0)} }
+func (t *idealIntType) Zero() Value { return &idealIntV{idealZero} }
 
 /*
  * Float
@@ -393,12 +401,12 @@ func (t *floatType) Zero() Value {
 	panic("unexpected float bit count")
 }
 
-var maxFloat32Val = bignum.MakeRat(bignum.Int(0xffffff).Shl(127-23), bignum.Nat(1))
-var maxFloat64Val = bignum.MakeRat(bignum.Int(0x1fffffffffffff).Shl(1023-52), bignum.Nat(1))
-var minFloat32Val = maxFloat32Val.Neg()
-var minFloat64Val = maxFloat64Val.Neg()
+var maxFloat32Val *big.Rat
+var maxFloat64Val *big.Rat
+var minFloat32Val *big.Rat
+var minFloat64Val *big.Rat
 
-func (t *floatType) minVal() *bignum.Rational {
+func (t *floatType) minVal() *big.Rat {
 	bits := t.Bits
 	if bits == 0 {
 		bits = uint(8 * unsafe.Sizeof(float(0)))
@@ -413,7 +421,7 @@ func (t *floatType) minVal() *bignum.Rational {
 	panic("unreachable")
 }
 
-func (t *floatType) maxVal() *bignum.Rational {
+func (t *floatType) maxVal() *big.Rat {
 	bits := t.Bits
 	if bits == 0 {
 		bits = uint(8 * unsafe.Sizeof(float(0)))
@@ -451,7 +459,7 @@ func (t *idealFloatType) isIdeal() bool { return true }
 
 func (t *idealFloatType) String() string { return "ideal float" }
 
-func (t *idealFloatType) Zero() Value { return &idealFloatV{bignum.Rat(1, 0)} }
+func (t *idealFloatType) Zero() Value { return &idealFloatV{big.NewRat(0, 1)} }
 
 /*
  * String
@@ -1221,6 +1229,15 @@ func (t *MultiType) Zero() Value {
  */
 
 func init() {
+	numer := big.NewInt(0xffffff)
+	numer.Lsh(numer, 127-23)
+	maxFloat32Val = new(big.Rat).SetInt(numer)
+	numer.SetInt64(0x1fffffffffffff)
+	numer.Lsh(numer, 1023-52)
+	maxFloat64Val = new(big.Rat).SetInt(numer)
+	minFloat32Val = new(big.Rat).Neg(maxFloat32Val)
+	minFloat64Val = new(big.Rat).Neg(maxFloat64Val)
+
 	// To avoid portability issues all numeric types are distinct
 	// except byte, which is an alias for uint8.
 
diff --git a/src/pkg/exp/eval/util.go b/src/pkg/exp/eval/util.go
deleted file mode 100644
index ffe13e1702..0000000000
--- a/src/pkg/exp/eval/util.go
+++ /dev/null
@@ -1,39 +0,0 @@
-// Copyright 2009 The Go Authors.  All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package eval
-
-import (
-	"exp/bignum"
-)
-
-// TODO(austin): Maybe add to bignum in more general form
-func ratToString(rat *bignum.Rational) string {
-	n, dnat := rat.Value()
-	d := bignum.MakeInt(false, dnat)
-	w, frac := n.QuoRem(d)
-	out := w.String()
-	if frac.IsZero() {
-		return out
-	}
-
-	r := frac.Abs()
-	r = r.Mul(bignum.Nat(1e6))
-	dec, tail := r.DivMod(dnat)
-	// Round last digit
-	if tail.Cmp(dnat.Div(bignum.Nat(2))) >= 0 {
-		dec = dec.Add(bignum.Nat(1))
-	}
-	// Strip zeros
-	ten := bignum.Nat(10)
-	for !dec.IsZero() {
-		dec2, r2 := dec.DivMod(ten)
-		if !r2.IsZero() {
-			break
-		}
-		dec = dec2
-	}
-	out += "." + dec.String()
-	return out
-}
diff --git a/src/pkg/exp/eval/value.go b/src/pkg/exp/eval/value.go
index dce4bfcf3d..cace2fd37b 100644
--- a/src/pkg/exp/eval/value.go
+++ b/src/pkg/exp/eval/value.go
@@ -5,7 +5,7 @@
 package eval
 
 import (
-	"exp/bignum"
+	"big"
 	"fmt"
 )
 
@@ -40,7 +40,7 @@ type IntValue interface {
 // because ideals are not l-values.
 type IdealIntValue interface {
 	Value
-	Get() *bignum.Integer
+	Get() *big.Int
 }
 
 type FloatValue interface {
@@ -51,7 +51,7 @@ type FloatValue interface {
 
 type IdealFloatValue interface {
 	Value
-	Get() *bignum.Rational
+	Get() *big.Rat
 }
 
 type StringValue interface {
@@ -272,7 +272,7 @@ func (v *intV) Set(t *Thread, x int64) { *v = intV(x) }
  */
 
 type idealIntV struct {
-	V *bignum.Integer
+	V *big.Int
 }
 
 func (v *idealIntV) String() string { return v.V.String() }
@@ -281,7 +281,7 @@ func (v *idealIntV) Assign(t *Thread, o Value) {
 	v.V = o.(IdealIntValue).Get()
 }
 
-func (v *idealIntV) Get() *bignum.Integer { return v.V }
+func (v *idealIntV) Get() *big.Int { return v.V }
 
 /*
  * Float
@@ -322,16 +322,16 @@ func (v *floatV) Set(t *Thread, x float64) { *v = floatV(x) }
  */
 
 type idealFloatV struct {
-	V *bignum.Rational
+	V *big.Rat
 }
 
-func (v *idealFloatV) String() string { return ratToString(v.V) }
+func (v *idealFloatV) String() string { return v.V.FloatString(6) }
 
 func (v *idealFloatV) Assign(t *Thread, o Value) {
 	v.V = o.(IdealFloatValue).Get()
 }
 
-func (v *idealFloatV) Get() *bignum.Rational { return v.V }
+func (v *idealFloatV) Get() *big.Rat { return v.V }
 
 /*
  * String
@@ -586,8 +586,6 @@ func (v multiV) Assign(t *Thread, o Value) {
  * Universal constants
  */
 
-// TODO(austin) Nothing complains if I accidentally define init with
-// arguments.  Is this intentional?
 func init() {
 	s := universe