Accurate decimal-to-float parsing routines.

This commit primarily adds implementations of the algorithms from William
Clinger's paper "How to Read Floating Point Numbers Accurately". It also
includes a lot of infrastructure necessary for those algorithms, and some
unit tests.

Since these algorithms reject a few (extreme) inputs that were previously
accepted, this could be seen as a [breaking-change]

1 files changed, 52 insertions, 0 deletions

diff --git a/src/libcoretest/num/dec2flt/parse.rs b/src/libcoretest/num/dec2flt/parse.rs
new file mode 100644
index 00000000000..09acf2bc517
--- /dev/null
+++ b/src/libcoretest/num/dec2flt/parse.rs
@@ -0,0 +1,52 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::iter;
+use core::num::dec2flt::parse::{Decimal, parse_decimal};
+use core::num::dec2flt::parse::ParseResult::{Valid, Invalid};
+
+#[test]
+fn missing_pieces() {
+    let permutations = &[".e", "1e", "e4", "e", ".12e", "321.e", "32.12e+", "12.32e-"];
+    for &s in permutations {
+        assert_eq!(parse_decimal(s), Invalid);
+    }
+}
+
+#[test]
+fn invalid_chars() {
+    let invalid = "r,?<j";
+    let valid_strings = &["123", "666.", ".1", "5e1", "7e-3", "0.0e+1"];
+    for c in invalid.chars() {
+        for s in valid_strings {
+            for i in 0..s.len() {
+                let mut input = String::new();
+                input.push_str(s);
+                input.insert(i, c);
+                assert!(parse_decimal(&input) == Invalid, "did not reject invalid {:?}", input);
+            }
+        }
+    }
+}
+
+#[test]
+fn valid() {
+    assert_eq!(parse_decimal("123.456e789"), Valid(Decimal::new(b"123", b"456", 789)));
+    assert_eq!(parse_decimal("123.456e+789"), Valid(Decimal::new(b"123", b"456", 789)));
+    assert_eq!(parse_decimal("123.456e-789"), Valid(Decimal::new(b"123", b"456", -789)));
+    assert_eq!(parse_decimal(".050"), Valid(Decimal::new(b"", b"050", 0)));
+    assert_eq!(parse_decimal("999"), Valid(Decimal::new(b"999", b"", 0)));
+    assert_eq!(parse_decimal("1.e300"), Valid(Decimal::new(b"1", b"", 300)));
+    assert_eq!(parse_decimal(".1e300"), Valid(Decimal::new(b"", b"1", 300)));
+    assert_eq!(parse_decimal("101e-33"), Valid(Decimal::new(b"101", b"", -33)));
+    let zeros: String = iter::repeat('0').take(25).collect();
+    let s = format!("1.5e{}", zeros);
+    assert_eq!(parse_decimal(&s), Valid(Decimal::new(b"1", b"5", 0)));
+}