The aim of this project is to allow adults and children to write code in a familiar high level language that can then be compiled to run on an arbitrary embedded system - that is devices with very low power CPUs and very little memory. (ie devices too small to host a python interpreter/runtime)
It's pre-alpha at the moment. However, as of Sept 2016, it's beginning to be usable for compiling very simple python programs that can run directly on an arduino, starting with those that can control servos. This means small python powered robots :)
It will be useful in supporting things like the The Scout Association's "Digital Maker" badge. That's a fair way off though.
Currently it can compile very very simple types of python program that looks like this into an equivalent (simple) C++ program.
Example program:
age = 10
new_age = 10 +1
new_age_too = age + 1
new_age_three = age + new_age_too
foo = "Hello"
bar = "World"
foobar = foo + bar
print(10-1-2,7)
print(1+2*3*4-5/7,25)
print(age, new_age, new_age_too)
print(foo, bar, foobar)
countdown = 2147483647
print("COUNTING DOWN")
while countdown:
countdown = countdown - 1
print("BLASTOFF")
Example results:
#include <iostream>
#include <string>
using namespace std;
int main(int argc, char *argv[])
{
int age;
string bar;
int countdown;
string foo;
string foobar;
int new_age;
int new_age_three;
int new_age_too;
age = 10;
new_age = (10+1);
new_age_too = (age+1);
new_age_three = (age+new_age_too);
foo = "Hello";
bar = "World";
foobar = (foo+bar);
cout << ((10-1)-2) << " " << 7 << endl;
cout << ((1+((2*3)*4))-(5/7)) << " " << 25 << endl;
cout << age << " " << new_age << " " << new_age_too << endl;
cout << foo << " " << bar << " " << foobar << endl;
countdown = 2147483647;
cout << "COUNTING DOWN" << endl;
while(countdown) {
countdown = (countdown-1);
};
cout << "BLASTOFF" << endl;
return 0;
}
Currently:
- Recognise simple sequential python programs with simple statements
- Can handle basic conditionals and while loops
- Custom includes, and function calls to C/C++ functions (within limits)
- Parse those to an AST
- Can represent equivalent C programs using a concrete C representation (CST)
- Can translate the AST to the CST and then generate C++ code from the CST
Python structural things it supports:
- While loop statements
- Comparisons
- If/elif/elif/else statements
- For loops - specific for X in range(Y)
- Function calls into libraries that we link with
This is close to allowing actually useful programs now.
It's a starting point, not the end point. For that, take a look at the language spec.
Pyxie is intended to be a simple Python to C++ compiler, with a target of compiling python code such that it can run on a microcontroller - like Arduino, MSP430 or ARM mbed type devices.
The name is a play on words. Specifically, Python to C++ - can be py2cc or pycc. If you try pronouncing "pycc" it can be "pic", "py cc" or pyc-c". The final one leads to Pixie.
This is unlikely to ever be a completely general python to C++ compiler - if you're after than look at Shed Skin, or things like Cython, Pyrex, and PyPy. (in terms of diminishing similarity) The difference this project has from those is that this project assumes a very small target device. Something along the lines of an Atmega 8A, Atmega 328 or more capable.
In the past I've written a test driven compiler suite, so I'll be following the same approach here. It did consider actually making Pyxie use that as a frontend, but for the moment, I'd like python compatibility.
Why not micropython? Micropython is ace . If your device is large enough to support the micropython runtime, use it! The aim of this is on the really small microcontrollers- the ones too small to even support micropython - like an MSP430, or an Atmega 8A or similarly tiny MCU.
In the past I've written a test driven compiler suite, so I'll be following the same approach here. It did consider actually making Pyxie use that as a frontend, but for the moment, I'd like python compatibility.
For the impatient: this probably does NOT do what you want, yet.
High level view of support:
- Supports variables, sequence, and assignment
- while loops controlled by expressions, possibly involving variables
- while loops can contain break/continue which allows "if" style functionality
- Also have basic conditional operators like "==", "!=", etc.
- Ability to pull in C++ includes on standard paths
This means we can almost start writing useful programs, but in particular can start creating simplistic benchmarks for measuring run speed. It IS getting there however, and feedback, usecases, devices very welcome.
Many moons ago, I made a generic language parser which I called SWP (semantic whitespace parser), or Gloop.
- https://github.com/sparkslabs/minisnips/tree/master/SWP
- http://www.slideshare.net/kamaelian/swp-a-generic-language-parser
It was an experiment to see if you could write a parser that had no keywords, or similar, in a completely test driven fashion. ie a bit like a parser for a Lisp like language that would look like python or ruby. It turns out that you can and there's lots of interesting things that arise if you do. (Best seen in the slideshare link)
It's not a complete subset of any particular python, but it's based around the intersection points in python 2 and 3. It will be, by definition, a non-dynamic subset - at least at first.
- For detail as to what's planned for the language, take a look at the language spec.
- For an overview as to the guiding principles, please take a look at project status
- For detail as to what's actually implemented, take a look at language status
These are all a WIP, but becoming more solid.
Personally, having built something simpler in the past, I know I'd find it useful. (I use python rather than C++ often because I can write more quicker with the former). Also, I work with kids in my spare time, and it opens up options there.
I've written something like this for work last year, but that was much more limited and restricted in both aspiration and implementation. This rewrite is something I've done on my own time, with my own tools, from scratch, which allows me to share this with others.
Major changes:
- This aims to be a more rounded implementation
- This performs transforms from an AST (abstract syntax tree) to a CCR (concrete code representation), rather than munging code directly from a concrete parse tree.
That potentially allows other things, like creation of visual representations of programs from code as well.
No. It could be used by others, but it's got a definite goal - to allow the use of a "little" python to program devices which are too small to host a python runtime.
If anything, it's a continuation of the personal itch around SWP (mentioned above) from about 10 years ago. Unlike that though, it's much, much better structured.
One thing that may happen though is the ability to take python classes and derive iotoy device implementations/interfaces directly. (since iotoy was inspired heavily by python introspection) That's quite some time off.
Release History:
- 0.1.26 - UNRELEASED - TBD
- 0.1.25 - 2018-02-03 - Major changes to internal representation and some new examples
- 0.1.24 - 2016-11-10 - Fix assignment in else/elif, update to support Ubuntu 16.04LTS, initial steps on function/def statement support
- 0.1.23 - 2016-10-11 - Major arduino profile improvements, print-as-function not statement
- 0.0.22 - 2016-09-25 - Enable ability to use a variety of Arduino boards by using an Makefile.in file
- 0.0.21 - 2016-09-17 - Adds ability to control Arduino servo objects. Quite a lot of internal changes to support that
- 0.0.20 - 2016-08-12 - Mainly internal changes. Adds WIPNOTES, updates arduino examples
- 0.0.19 - 2016-01-31 - Continued work on arduino profile and initial Python3 support
- 0.0.18 - 2016-01-10 - Grammar changes to support object attributes and methods, start of servo support in arduino profile.
- 0.0.17 - 2015-08-12 - Add pass statement, enable "for" on arduino, update documentation, refactor pyxie harness
- 0.0.16 - 2015-08-02 - Adds initial Arduino LEONARDO support, improved function call, release build scripts
- 0.0.15 - 2015-07-18 - clib converted to py clib for adding to build directory
- 0.0.14 - 2015-07-18 - For loops implemented. Added clib code, C++ generator implementation, FOR loop style test harness, parsing and basic analysis of of FOR loops using a range interator
- 0.0.13 - 2015-06-21 - if/elif/else,conditionals/boolean/parenthesised expressions.
- 0.0.12 - 2015-06-16 - While loops, break/continue, Website, comparison operators, simple benchmark test
- 0.0.11 - 2015-06-06 - Function calls; inclusion of custom C++ headers; empty statements; language spec updates
- 0.0.10 - 2015-06-03 - Analysis phase to make type inference work better. Lots of related changes. Implementation of expression statements.
- 0.0.9 - 2015-05-23 - Grammar changed to be left, not right recursive. (Fixes precedence in un-bracketed expressions) Added standalone compilation mode - outputs binaries from python code.
- 0.0.8 - 2015-05-13 - Internally switch over to using node objects for structure - resulting in better parsing of expressions with variables and better type inference.
- 0.0.7 - 2015-04-29 - Structural, testing improvements, infix operators expressions (+ - * / ) for integers, precdence fixes
- 0.0.6 - 2015-04-26 - Character Literals, "plus" expressions, build/test improvements
- 0.0.5 - 2015-04-23 - Core lexical analysis now matches language spec, including blocks
- 0.0.4 - 2015-04-22 - Mixed literals in print statements
- 0.0.3 - 2015-04-21 - Ability to print & work with a small number of variables
- 0.0.2 - 2015-03-30 - supports basic assignment
- 0.0.1 - Unreleased - rolled into 0.0.2 - Initial structure
program : statements
statements : statement
| statement statements
statement_block : INDENT statements DEDENT
statement : assignment_statement
| general_expression
| EOL
| while_statement
| break_statement
| continue_statement
| pass_statement
| if_statement
| for_statement
assignment_statement : IDENTIFIER ASSIGN general_expression # ASSIGN is currently limited to "="
while_statement : WHILE general_expression COLON EOL statement_block
break_statement : BREAK
pass_statement : PASS
continue_statement : CONTINUE
if_statement : IF general_expression COLON EOL statement_block
| IF general_expression COLON EOL statement_block extended_if_clauses
extended_if_clauses : else_clause
| elif_clause
else_clause : ELSE COLON EOL statement_block
elif_clause : ELIF general_expression COLON EOL statement_block
| ELIF general_expression COLON EOL statement_block extended_if_clauses
# NOTE: print_statement has been removed and replaced by python 3 style function
for_statement : FOR IDENTIFIER IN general_expression COLON EOL statement_block
expr_list : general_expression
| general_expression COMMA expr_list
general_expression : boolean_expression
boolean_expression : boolean_and_expression
| boolean_expression OR boolean_and_expression
boolean_and_expression : boolean_not_expression
| boolean_and_expression AND boolean_not_expression
boolean_not_expression : relational_expression
| NOT boolean_not_expression
relational_expression : expression
| relational_expression COMPARISON_OPERATOR expression
expression : arith_expression
| expression '+' arith_expression
| expression '-' arith_expression
| expression '**' arith_expression
arith_expression : negatable_expression_atom
| arith_expression '*' negatable_expression_atom
| arith_expression '/' negatable_expression_atom
negatable_expression_atom : "-" negatable_expression_atom
| expression_molecule
expression_molecule : expression_atom
| bracketed_expression
expression_atom : value_literal
| expression_atom '(' expr_list ')' # Function call
| expression_atom '(' ')' # Function call, with no arguments
bracketed_expression : PARENL general_expression PARENR
value_literal : number
| STRING
| CHARACTER
| BOOLEAN
| identifiable
identifiable : IDENTIFIER
| expression_molecule dotexpression
dotexpression : DOT IDENTIFIER
number : NUMBER
| FLOAT
| HEX
| OCTAL
| BINARY
| LONG (suffice is L)
| UNSIGNEDLONG (suffice is l)
| '-' number
Current Lexing rules used by the grammar:
NUMBER : \d+ FLOAT : \d+.\d+ # different from normal python, which allows .1 and 1. HEX : 0x([abcdef]|\d)+ OCTAL : 0o\d+ BINARY : 0b\d+ STRING - "([^\"]|\.)*" or '([^\']|\.)*' # single/double quote strings, with escaped values CHARACTER : c'.' / c"." # Simplification - can be an escaped character BOOLEAN : True|False IDENTIFIER : [a-zA-Z_][a-zA-Z0-9_]*
Most expressions currently rely on the C++ counterparts. As a result not all combinations which are valid are directly supported yet. Notable ones:
- Combinations of strings with other strings (outlawing /*, etc)
- Combinations of strings with numbers
Python 2 has a print statement. Python 3 doesn't. In early days of Pyxie, Pyxie supported a python 2 statement to make life easier before function calls were implemented, with a note to say that "print" as a statement would disappear.
As of 0.1.23, the print_statement has been removed. As well as being simplifying the syntax, it also means that Arudino statements like Serial.print now become legal statements.
Michael Sparks, February 2018