From 6ed4581f545069488446682ee9b052798626327d Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Tue, 13 Jun 2017 13:36:56 +1000
Subject: [PATCH] py/formatfloat: Fix number of digits and exponent sign when
rounding.
This patch fixes 2 things when printing a floating-point number that
requires rounding up of the mantissa:
- retain the correct precision; eg 0.99 becomes 1.0, not 1.00
- if the exponent goes from -1 to 0 then render it as +0, not -0
---
py/formatfloat.c | 7 ++++++-
tests/float/string_format_modulo.py | 3 +++
tests/float/string_format_modulo3.py | 3 +--
tests/float/string_format_modulo3.py.exp | 3 +--
4 files changed, 11 insertions(+), 5 deletions(-)
diff --git a/py/formatfloat.c b/py/formatfloat.c
index 9ff80d9f6..b16746b39 100644
--- a/py/formatfloat.c
+++ b/py/formatfloat.c
@@ -376,11 +376,16 @@ int mp_format_float(FPTYPE f, char *buf, size_t buf_size, char fmt, int prec, ch
rs[1] = '0';
if (e_sign == '-') {
e--;
+ if (e == 0) {
+ e_sign = '+';
+ }
} else {
e++;
}
+ } else {
+ // Need at extra digit at the end to make room for the leading '1'
+ s++;
}
- s++;
char *ss = s;
while (ss > rs) {
*ss = ss[-1];
diff --git a/tests/float/string_format_modulo.py b/tests/float/string_format_modulo.py
index 03c8dd00a..aea534247 100644
--- a/tests/float/string_format_modulo.py
+++ b/tests/float/string_format_modulo.py
@@ -44,3 +44,6 @@ print(('%.40g' % 1e-3)[:2])
print(('%.40g' % 1e-4)[:2])
print("%.0g" % 1) # 0 precision 'g'
+
+print('%.1e' % 9.99) # round up with positive exponent
+print('%.1e' % 0.999) # round up with negative exponent
diff --git a/tests/float/string_format_modulo3.py b/tests/float/string_format_modulo3.py
index 563964786..5d26f2575 100644
--- a/tests/float/string_format_modulo3.py
+++ b/tests/float/string_format_modulo3.py
@@ -1,4 +1,3 @@
# uPy and CPython outputs differ for the following
print("%.1g" % -9.9) # round up 'g' with '-' sign
-print("%.1e" % 9.99) # round up with positive exponent
-print("%.1e" % 0.999) # round up with negative exponent
+print("%.2g" % 99.9) # round up
diff --git a/tests/float/string_format_modulo3.py.exp b/tests/float/string_format_modulo3.py.exp
index b158c7d7f..71432b340 100644
--- a/tests/float/string_format_modulo3.py.exp
+++ b/tests/float/string_format_modulo3.py.exp
@@ -1,3 +1,2 @@
-10
-1.00e+01
-1.00e-00
+100
--
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