From 86009c70c8f182d0138e89cd3f52e59604a3ee5b Mon Sep 17 00:00:00 2001
From: Stephen Chung <Stephen.Chung@intexact.com>
Date: Mon, 23 Nov 2020 22:51:21 +0800
Subject: [PATCH] Allow floating point numbers ending in a period.

---
 doc/src/language/numbers.md | 19 ++++++++++---------
 src/token.rs                | 23 ++++++++++++++++++++---
 tests/float.rs              |  1 +
 3 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/doc/src/language/numbers.md b/doc/src/language/numbers.md
index 388d3e77..33c3c930 100644
--- a/doc/src/language/numbers.md
+++ b/doc/src/language/numbers.md
@@ -8,14 +8,15 @@ Integer numbers follow C-style format with support for decimal, binary ('`0b`'),
 The default system integer type (also aliased to `INT`) is `i64`. It can be turned into `i32` via the [`only_i32`] feature.
 
 Floating-point numbers are also supported if not disabled with [`no_float`]. The default system floating-point type is `i64`
-(also aliased to `FLOAT`).
+(also aliased to `FLOAT`). It can be turned into `f32` via the [`f32_float`] feature.
 
-'`_`' separators can be added freely and are ignored within a number.
+'`_`' separators can be added freely and are ignored within a number - except at the very beginning or right after
+a decimal point ('`.`').
 
-| Format           | Type             |
-| ---------------- | ---------------- |
-| `123_345`, `-42` | `i64` in decimal |
-| `0o07_76`        | `i64` in octal   |
-| `0xabcd_ef`      | `i64` in hex     |
-| `0b0101_1001`    | `i64` in binary  |
-| `123_456.789`    | `f64`            |
+| Format                | Type             |
+| --------------------- | ---------------- |
+| `123_345`, `-42`      | `INT` in decimal |
+| `0o07_76`             | `INT` in octal   |
+| `0xabcd_ef`           | `INT` in hex     |
+| `0b0101_1001`         | `INT` in binary  |
+| `123_456.789`, `-42.` | `FLOAT`          |
diff --git a/src/token.rs b/src/token.rs
index aad19ef2..2433a35c 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -1056,14 +1056,31 @@ fn get_next_token_inner(
                         '.' => {
                             stream.get_next().unwrap();
 
-                            // Check if followed by digits (or _)
+                            // Check if followed by digits or something that cannot start a property name
                             match stream.peek_next().unwrap_or('\0') {
-                                '0'..='9' | '_' => {
+                                // digits after period - accept the period
+                                '0'..='9' => {
                                     result.push(next_char);
                                     pos.advance()
                                 }
+                                // _ - cannot follow a decimal point
+                                '_' => {
+                                    stream.unread(next_char);
+                                    break;
+                                }
+                                // .. - reserved symbol, not a floating-point number
+                                '.' => {
+                                    stream.unread(next_char);
+                                    break;
+                                }
+                                // symbol after period - probably a float
+                                ch @ _ if !is_id_first_alphabetic(ch) => {
+                                    result.push(next_char);
+                                    pos.advance();
+                                    result.push('0');
+                                }
+                                // Not a floating-point number
                                 _ => {
-                                    // Not a floating-point number
                                     stream.unread(next_char);
                                     break;
                                 }
diff --git a/tests/float.rs b/tests/float.rs
index 1e973e29..7c5a4c2f 100644
--- a/tests/float.rs
+++ b/tests/float.rs
@@ -15,6 +15,7 @@ fn test_float() -> Result<(), Box<EvalAltResult>> {
         engine.eval::<bool>("let x = 0.0; let y = 1.0; x > y")?,
         false
     );
+    assert_eq!(engine.eval::<bool>("let x = 0.; let y = 1.; x > y")?, false);
     assert!((engine.eval::<FLOAT>("let x = 9.9999; x")? - 9.9999 as FLOAT).abs() < EPSILON);
 
     Ok(())