Support scientific notation floats

scanner/scanner.go

@@ -190,7 +190,8 @@ func (s *scanner) scanNumber() (int, []byte, error) {
 		return 0, nil, err
 	} else if s.c != '.' {
 		s.unread()
-		return TNUMBER, s.scratch[0:n], nil
+		//  We can't just return.  The number could be 1e-1
+		return s.scanScientific(n)
 	}
 	s.scratch[n] = '.'
 	n++
@@ -207,6 +208,47 @@ func (s *scanner) scanNumber() (int, []byte, error) {
 	}
 	n++
 
+	return s.scanScientific(n)
+}
+
+func (s *scanner) scanScientific(n int) (int, []byte, error) {
+	// Read scientific
+	if err := s.read(); err == io.EOF {
+		return TNUMBER, s.scratch[0:n], nil
+	} else if err != nil {
+		return 0, nil, err
+	} else if s.c != 'e' && s.c != 'E' {
+		s.unread()
+		return TNUMBER, s.scratch[0:n], nil
+	}
+	s.scratch[n] = 'e'
+	n++
+
+	// Read sign
+	if err := s.read(); err == io.EOF {
+		return TNUMBER, s.scratch[0:n], nil
+	} else if err != nil {
+		return 0, nil, err
+	} else if s.c != '-' && s.c != '+' {
+		s.unread()
+	} else if s.c == '-' { // don't bother adding the +
+		s.scratch[n] = '-'
+		n++
+	}
+
+	if err := s.read(); err != nil {
+		return 0, nil, err
+	}
+
+	// Read whole number.
+	if err := s.scanDigits(&n); err == io.EOF {
+		return TNUMBER, s.scratch[0:n], nil
+	} else if err != nil {
+		fmt.Println("Bad?")
+		return 0, nil, err
+	}
+	n++
+
 	return TNUMBER, s.scratch[0:n], nil
 }
 

scanner/scanner_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"strconv"
 )
 
 // Ensures that a positive number can be scanned.
@@ -33,6 +34,31 @@ func TestScanFloat(t *testing.T) {
 	assert.Equal(t, string(b), "120.12931")
 }
 
+// Ensures that a fractional number in scientific notation can be scanned.
+func TestScanFloatScientific(t *testing.T) {
+	tok, b, err := NewScanner(strings.NewReader("10.1e01")).Scan()
+	assert.NoError(t, err)
+	assert.Equal(t, tok, TNUMBER)
+	assert.Equal(t, string(b), "10.1e01")
+
+	tok, b, err = NewScanner(strings.NewReader("10.1e-01")).Scan()
+	assert.NoError(t, err)
+	assert.Equal(t, tok, TNUMBER)
+	assert.Equal(t, string(b), "10.1e-01")
+
+	tok, b, err = NewScanner(strings.NewReader("10.1e+01")).Scan()
+	assert.NoError(t, err)
+	assert.Equal(t, tok, TNUMBER)
+	assert.Equal(t, string(b), "10.1e01")
+	f, _ := strconv.ParseFloat(string(b), 64)
+	assert.Equal(t, 10.1e+01, f)
+
+	tok, b, err = NewScanner(strings.NewReader("-1e1")).Scan()
+	assert.NoError(t, err)
+	assert.Equal(t, tok, TNUMBER)
+	assert.Equal(t, string(b), "-1e1")
+}
+
 // Ensures that a quoted string can be scanned.
 func TestScanString(t *testing.T) {
 	tok, b, err := NewScanner(strings.NewReader(`"hello world"`)).Scan()