Mu functions or 'recipes' are lists of instructions, one to a line. Each
instruction operates on some *ingredients* and returns some *products*.
```
[products] <- instruction [ingredients]
```
Result and ingredient *reagents* have to be variables. But you can have any
number of them. In particular you can have any number of products. For example,
you can perform integer division as follows:
```
quotient:number, remainder:number <- divide-with-remainder 11, 3
```
Each reagent can provide a name as well as its type separated by a colon. You
only have to specify the type the first time you mention a name, but you can
be more explicit if you choose. Types can be multiple words, like:
```nim
x:array:number:3 # x is an array of 3 numbers
y:list:number # y is a list of numbers
```
Recipes load their ingredients from their caller using the *next-ingredient*
instruction, and return products using *reply*.
Try out the factorial program now:
```shell
$ ./mu factorial.mu
result: 120 # factorial of 5
```
You can also run its unit tests:
```shell
$ ./mu test factorial.mu
```
Here's what one of the tests inside `factorial.mu` looks like:
Every test conceptually spins up a really lightweight virtual machine, so you
can do things like check the value of specific locations in memory. You can
also print to screen and check that the screen contains what you expect at the
end of a test. For example, `chessboard.mu` checks the initial position of a
game of chess (delimiting the edges of the screen with periods):
Similarly you can fake the keyboard to pretend someone typed something:
```
assume-keyboard [a2-a4]
```
As we add a file system, graphics, audio, network support and so on, we'll
augme# Copyright (C) 2009, 2010 Roman Zimbelmann <romanz@lavabit.com>
#
# This program 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, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
NAME = ranger
VERSION = $(shell grep -m 1 -o '[0-9][0-9.]\+' README)
SNAPSHOT_NAME ?= $(NAME)-$(VERSION)-$(shell git rev-parse HEAD | cut -b 1-8).tar.gz
# Find suitable python version (need python >= 2.6 or 3.1):
PYTHON ?= $(shell python -c 'import sys; sys.exit(sys.version < "2.6")' && \
which python || which python3.1 || which python3 || which python2.6)
SETUPOPTS ?= '--record=install_log.txt'
DOCDIR ?= doc/pydoc
DESTDIR ?= /
PYOPTIMIZE ?= 1
BMCOUNT ?= 5 # how often to run the benchmarks?
CWD = $(shell pwd)
default: compile
@echo 'Run `make options` for a list of all options'
options: help
@echo
@echo 'Options:'
@echo 'PYTHON = $(PYTHON)'
@echo 'PYOPTIMIZE = $(PYOPTIMIZE)'
@echo 'DOCDIR = $(DOCDIR)'
help:
@echo 'make install: Install $(NAME)'
@echo 'make doc: Create the pydoc documentation'
@echo 'make clean: Remove the compiled files (*.pyc, *.pyo)'
@echo 'make cleandoc: Remove the pydoc documentation'
@echo 'make snapshot: Create a tar.gz of the current git revision'
@echo