[Gambas-bugtracker] Bug #1562: Bad calculation

[bugtracker at gambaswiki.org]

http://gambaswiki.org/bugtracker/edit?object=BUG.1562&from=L21haW4-

juan JUAN reported a new bug.

Summary
-------

Bad calculation

Type             : Bug
Priority         : Medium
Gambas version   : Unknown
Product          : Unknown


Description
-----------

GAMBAS 3.13.0

Public Sub Main()

  Dim a As Float
  Dim b As Float
  Dim c As Float

  a = -1
  b = ACos(a)
  Print a, b

  a = a + 1e-16
  c = ACos(a)
  Print a, c

  Print b - c

End


OUTPUT:
-1      3,14159265358979
-1      3,14159263868863
1,49011611938477E-8                (!!¿?!!)


System information
------------------

[System]
Gambas=3.13
OperatingSystem=Linux
Kernel=4.19.0-4-amd64
Architecture=x86_64
Distribution=debian buster/sid
Desktop=KDE5
Theme=Oxygen
Language=es_ES.UTF-8
Memory=1993M

[Libraries]
Cairo=libcairo.so.2.11600.0
Curl=libcurl.so.4.5.0
DBus=libdbus-1.so.3.19.9
GStreamer=libgstreamer-1.0.so.0.1404.0
GTK+2=libgtk-x11-2.0.so.0.2400.32
GTK+3=libgtk-3.so.0.2404.1
OpenGL=libGL.so.1.7.0
Poppler=libpoppler.so.82.0.0
QT4=libQtCore.so.4.8.7
QT5=libQt5Core.so.5.11.3
SDL=libSDL-1.2.so.0.11.4
SQLite=libsqlite3.so.0.8.6

[Environment]
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
DESKTOP_SESSION=/usr/share/xsessions/plasma
DISPLAY=:0
GB_GUI=gb.qt5
GPG_AGENT_INFO=/run/user/1000/gnupg/S.gpg-agent:0:1
GS_LIB=<home>/.fonts
GTK2_RC_FILES=/etc/gtk-2.0/gtkrc:<home>/.gtkrc-2.0:<home>/.config/gtkrc-2.0
GTK_RC_FILES=/etc/gtk/gtkrc:<home>/.gtkrc:<home>/.config/gtkrc
HOME=<home>
KDE_FULL_SESSION=true
KDE_SESSION_UID=1000
KDE_SESSION_VERSION=5
LANG=es_ES.UTF-8
LANGUAGE=es_ES.UTF-8
LOGNAME=<user>
MATHEMATICA_HOME=/usr/local/Wolfram/Mathematica/10.0
PAM_KWALLET5_LOGIN=/run/user/1000/kwallet5.socket
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
PWD=<home>
QT_ACCESSIBILITY=1
QT_AUTO_SCREEN_SCALE_FACTOR=0
SESSION_MANAGER=local/<hostname>:@/tmp/.ICE-unix/1219,unix/<hostname>:/tmp/.ICE-unix/1219
SHELL=/bin/bash
SHLVL=0
SSH_AGENT_PID=805
SSH_AUTH_SOCK=/tmp/ssh-09cTFjG2EqjA/agent.773
TZ=:/etc/localtime
USER=<user>
XAUTHORITY=/tmp/xauth-1000-_0
XCURSOR_SIZE=0
XCURSOR_THEME=Adwaita
XDG_CURRENT_DESKTOP=KDE
XDG_DATA_DIRS=/usr/share:/usr/share:/usr/local/share
XDG_RUNTIME_DIR=/run/user/1000
XDG_SEAT=seat0
XDG_SEAT_PATH=/org/freedesktop/DisplayManager/Seat0
XDG_SESSION_CLASS=user
XDG_SESSION_DESKTOP=KDE
XDG_SESSION_ID=3
XDG_SESSION_PATH=/org/freedesktop/DisplayManager/Session1
XDG_SESSION_TYPE=x11
XDG_VTNR=7