1 = Lichen = 2 3 || [[/Downloads|Downloads]] || [[#Language|Language]] || [[#Toolchain|Toolchain]] || [[#Rationale|Rationale]] || [[#Documents|Documents]] || 4 5 Lichen is both a Python-like [[/Design|language]] and a 6 [[/Toolchain|toolchain]] for that language. 7 8 Some objectives: 9 10 * Perform analysis on programs to better understand program structure and 11 behaviour 12 * Develop code generation capabilities 13 * Provide a platform for experimentation independent of existing Python 14 language and library implementations 15 * Provide independence from Python language evolution 16 * Learn things about writing compilers 17 18 Despite building on a long [[/History|history]] of experimentation, Lichen 19 still requires some [[/ToDo|work to be done]] for it to be more widely usable. 20 21 <<Anchor(Language)>> 22 == Language == 23 24 The Lichen language [[/Design|foregoes]] various dynamic aspects of Python to 25 provide a foundation upon which more predictable programs can be built, while 26 preserving essential functionality to make the core of the language seem very 27 much "like Python" (thus yielding the name "Lichen"). The general syntax is 28 largely identical to Python, with only certain syntactic constructs being 29 deliberately unsupported, largely because the associated features are not 30 desired. 31 32 <<Anchor(Toolchain)>> 33 == Toolchain == 34 35 The Lichen [[/Toolchain|toolchain]] employs existing tokeniser and parser 36 software to obtain an abstract syntax tree which is then inspected to provide 37 data to support deductions about the structure and nature of a given program. 38 With the information obtained from these processes, a program is then 39 constructed, consisting of a number of source files in the target compilation 40 language (which is currently the C programming language). This generated 41 program may be compiled and run, hopefully producing the results intended by 42 the source program's authors. 43 44 Lichen source files use the `.py` suffix since the language syntax is 45 superficially compatible with Python, allowing text editors to provide 46 highlighting and editing support for Lichen programs without the need to 47 reconfigure such tools. However, an alternative, recommended suffix is likely 48 to be introduced in future. 49 50 <<Anchor(Library)>> 51 == Library == 52 53 Unlike other Python compilation efforts, Lichen programs employ a newly-written 54 library that is distinct from the CPython standard library distribution and 55 completely independent from the CPython extension and object libraries on which 56 Python programs being run with CPython must depend. Thus, there is no 57 dependency on any `libpython` for run-time functionality. Since the parts of 58 the Python standard library that are written in Python tend to be rather 59 variable in quality, there has been no real inclination to re-use modules from 60 that particular source, noting that they would need modifying to be compatible 61 with Lichen, anyway. However, rewriting such modules provides opportunities to 62 "do things right": with some functionality being over twenty years old and in 63 bad shape, this is arguably something that should have been done for Python, 64 anyway. 65 66 <<Anchor(Rationale)>> 67 == Rationale == 68 69 Python has proven to be a readable, productive, comfortable-to-use and popular 70 programming language. However, as it has accumulated features, the precise 71 behaviour of programs making use of many of these features has become more 72 difficult to predict. Features added to provide even more convenience to the 73 programmer have often incurred run-time costs, introduced layers of 74 indirection, and have made programs even more inscrutable. Instead of 75 development tools reaching a point of being able to infer information about 76 programs, it has been suggested that programmers annotate their programs in 77 order to help tools understand those programs instead. Beyond superficial code 78 style analysis and providing tooltips in integrated development environments, 79 Python code analysis is often portrayed as a lost cause. 80 81 By employing a refined language [[/Design|design]], Lichen aims to let each 82 program define its [[/Structure|structure]] conveniently, be readily 83 [[/Inspection|inspected]], and thus support [[/Deduction|deductions]] about the 84 use of the program's objects by the code. The result should be more predictable 85 programs that can be [[/Translation|translated]] to other, more efficient, 86 [[/Representations|representations]]. The Lichen toolchain should be able to 87 tell the programmer useful things about their programs that it may also be able 88 to make use of itself. It not only aims to report information about programs 89 that might be of interest to the developer, but it seeks to produce 90 functioning, translated programs that can actually be run. 91 92 <<Anchor(Documents)>> 93 == Document Index == 94 95 <<PageList>>
