once.fz
# This file is part of the Fuzion language implementation.
#
# The Fuzion language implementation is free software: you can redistribute it
# and/or modify it under the terms of the GNU General Public License as published
# by the Free Software Foundation, version 3 of the License.
#
# The Fuzion language implementation is distributed in the hope that it will be
# useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
# License for more details.
#
# You should have received a copy of the GNU General Public License along with The
# Fuzion language implementation. If not, see <https://www.gnu.org/licenses/>.
# -----------------------------------------------------------------------
#
# Tokiwa Software GmbH, Germany
#
# Source code of Fuzion standard library feature once
#
# -----------------------------------------------------------------------
# executes `f` only the first time when
# calling `get` caching its result.
#
public once(LM type : mutate, T type, f Lazy T) is
cache := LM.env.new (option T) nil
# get the result of `f`
#
public get T =>
if cache.get.is_nil
cache <- f()
cache.get.get
last changed: 2025-01-23