num_option.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 num_option # # Author: Fridtjof Siebert (siebert@tokiwa.software) # # ----------------------------------------------------------------------- # num_option -- optional numeric values # # This is a pseudo-numeric type that handles one additional # value: nil. Any operation on nil will result in nil for a # numeric result or false for a boolean result. # public num_option(public T type : numeric) : choice T nil, monad T (num_option T) is # Does this option contain a value of type T? # public exists => (num_option.this ? T => true | nil => false) # short-hand postfix operator for 'exists' # public postfix ?? => exists # Does this option contain no value of type T? # public is_nil => !exists # short-hand postfix operator for 'is_nil' # public postfix !! => is_nil # value of an option that is known to contain a value # # this can only be called in cases where it is known for sure that this option # is not nil. A runtime error will be created otherwise. # public val T pre safety: (num_option.this??) => num_option.this ? v T => v | nil => fuzion.std.panic "num_option.val called on nil" # unwrap value or get default # public get (default Lazy T) => num_option.this ? v T => v | nil => default # monadic operator public redef infix >>= (f T -> num_option T) => num_option.this.bind T f # monadic operator # # Same as non-generic >>=, but also maps to a different type B. # public bind(B type : numeric, f T -> num_option B) num_option B => num_option.this ? v T => f v | nil => nil # monadic operator for bool result, false for nil public infix >>? (f T -> bool) => num_option.this ? v T => f v | nil => false # basic prefix operations public prefix +? num_option T => num_option.this >>= v -> +v public prefix -? num_option T => num_option.this >>= v -> -?v # basic infix operations public infix +? (other num_option T) num_option T => num_option.this >>= v -> other >>= w -> v +? w public infix -? (other num_option T) num_option T => num_option.this >>= v -> other >>= w -> v -? w public infix *? (other num_option T) num_option T => num_option.this >>= v -> other >>= w -> v *? w public infix **?(other num_option T) num_option T => num_option.this >>= v -> other >>= w -> v **? w public infix /? (other num_option T) num_option T pre safety: !other.is_zero => num_option.this >>= v -> other >>= w -> v / w public infix %? (other num_option T) num_option T pre safety: !other.is_zero => num_option.this >>= v -> other >>= w -> v % w # comparison public infix ==? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v = w public infix !=? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v != w public infix <? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v < w public infix <=? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v ≤ w public infix >? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v > w public infix >=? (other num_option T) bool => num_option.this >>? v -> other >>? w -> v ≥ w public is_zero => sign ==? 0 public sign num_option i32 => num_option.this ? v T => v.sign | nil => nil public abs num_option T => num_option.this >>= v -> if v.sign ≥ 0 v else -?v # converts num_option into a list of either a single element in case # num_option.this.exists or `nil`otherwise # public as_list list T => num_option.this ? v T => v : nil | nil => nil public redef as_string String => num_option.this ? v T => v.as_string | nil => "--no value--" # return function # public fixed type.return (a T) => num_option a # num_option with 1 argument provides an short-hand to wrap a value into a # num_option # # Using this enables to write # # o := num_option x # # instead of # # o num_option TypeOfX := x # public num_option(T type : numeric, o num_option T) => o