Fixes #30: Implement exp notation in floats

lexer.go

diff --git a/lexer.go b/lexer.go
index c1b4998..001049d 100644
--- a/lexer.go
+++ b/lexer.go
@@ -418,6 +418,7 @@
 		l.accept("-")
 	}
 	pointSeen := false
+	expSeen := false
 	digitSeen := false
 	for {
 		next := l.next()
@@ -429,6 +430,11 @@
 				return l.errorf("float cannot end with a dot")
 			}
 			pointSeen = true
+		} else if next == 'e' || next == 'E' {
+			expSeen = true
+			if !l.accept("+") {
+				l.accept("-")
+			}
 		} else if isDigit(next) {
 			digitSeen = true
 		} else {
@@ -443,7 +449,7 @@
 	if !digitSeen {
 		return l.errorf("no digit in that number")
 	}
-	if pointSeen {
+	if pointSeen || expSeen {
 		l.emit(tokenFloat)
 	} else {
 		l.emit(tokenInteger)

lexer_test.go

diff --git a/lexer_test.go b/lexer_test.go
index 5114223..019a496 100644
--- a/lexer_test.go
+++ b/lexer_test.go
@@ -305,6 +305,51 @@
 	})
 }
 
+func TestFloatWithExponent1(t *testing.T) {
+	testFlow(t, "a = 5e+22", []token{
+		token{Position{1, 1}, tokenKey, "a"},
+		token{Position{1, 3}, tokenEqual, "="},
+		token{Position{1, 5}, tokenFloat, "5e+22"},
+		token{Position{1, 10}, tokenEOF, ""},
+	})
+}
+
+func TestFloatWithExponent2(t *testing.T) {
+	testFlow(t, "a = 5E+22", []token{
+		token{Position{1, 1}, tokenKey, "a"},
+		token{Position{1, 3}, tokenEqual, "="},
+		token{Position{1, 5}, tokenFloat, "5E+22"},
+		token{Position{1, 10}, tokenEOF, ""},
+	})
+}
+
+func TestFloatWithExponent3(t *testing.T) {
+	testFlow(t, "a = -5e+22", []token{
+		token{Position{1, 1}, tokenKey, "a"},
+		token{Position{1, 3}, tokenEqual, "="},
+		token{Position{1, 5}, tokenFloat, "-5e+22"},
+		token{Position{1, 11}, tokenEOF, ""},
+	})
+}
+
+func TestFloatWithExponent4(t *testing.T) {
+	testFlow(t, "a = -5e-22", []token{
+		token{Position{1, 1}, tokenKey, "a"},
+		token{Position{1, 3}, tokenEqual, "="},
+		token{Position{1, 5}, tokenFloat, "-5e-22"},
+		token{Position{1, 11}, tokenEOF, ""},
+	})
+}
+
+func TestFloatWithExponent5(t *testing.T) {
+	testFlow(t, "a = 6.626e-34", []token{
+		token{Position{1, 1}, tokenKey, "a"},
+		token{Position{1, 3}, tokenEqual, "="},
+		token{Position{1, 5}, tokenFloat, "6.626e-34"},
+		token{Position{1, 14}, tokenEOF, ""},
+	})
+}
+
 func TestDoubleEqualKey(t *testing.T) {
 	testFlow(t, "foo= = 2", []token{
 		token{Position{1, 1}, tokenKey, "foo"},

parser_test.go

diff --git a/parser_test.go b/parser_test.go
index 8160905..238ca2f 100644
--- a/parser_test.go
+++ b/parser_test.go
@@ -70,6 +70,17 @@
 	})
 }
 
+func TestFloatsWithExponents(t *testing.T) {
+	tree, err := Load("a = 5e+22\nb = 5E+22\nc = -5e+22\nd = -5e-22\ne = 6.626e-34")
+	assertTree(t, tree, err, map[string]interface{}{
+		"a": float64(5e+22),
+		"b": float64(5E+22),
+		"c": float64(-5e+22),
+		"d": float64(-5e-22),
+		"e": float64(6.626e-34),
+	})
+}
+
 func TestSimpleDate(t *testing.T) {
 	tree, err := Load("a = 1979-05-27T07:32:00Z")
 	assertTree(t, tree, err, map[string]interface{}{