advanced syntax&semantics extension system for Python
Project description
Moshmosh
An advanced syntax extension system implemented in pure python.
pip install moshmosh-base
Preview
# moshmosh?
# Use extension
# +<extension name>[<extension arg>{','}]
<do stuff with your extensions>
# Unset extension
# -<extension name>[<extension arg>{','}]
The first line of the file should start with a comment # moshmosh?
, which tells us
that it's expected to use Moshmosh extension system.
Tips
The order of first-time enabling some extensions matters, the following one presents a valid order:
# moshmosh?
# +pattern-matching
# +quick-lambda
# +scoped-operator
# +template-python
# +pipeline
Unless you use parametric quick-lambda
like # +quick-lambda(it)
,
the first time to enable pattern-matching
should be prior to that of enabling quick-lambda
, and scoped-operator
, template-python
and pipeline
should be enabled for the first time after first-time enabling quick-lambda
.
Case Study : Pattern Matching
# moshmosh?
# +pattern-matching
class GreaterThan:
def __init__(self, v):
self.v = v
def __match__(self, cnt: int, to_match):
if isinstance(to_match, int) and cnt is 0 and to_match > self.v:
return () # matched
# 'return None' indicates 'unmatched'
with match(114, 514):
if (GreaterThan(42)() and a, b):
print(b, a)
The syntax of pattern matching:
# +pattern-matching(token_name='match')
with <token_name>(value):
if pat1:
body1
if pat2:
body2
...
The matching should be exhaustive, otherwise,
a moshmosh.extensions.pattern_matching.runtime.NotExhaustive
might get raised.
Supported Patterns:
- And pattern:
pat1 and pat2 and pat3 ...
- Or pattern:
pat1 or pat2 or pat3...
- Pin pattern:
pin(value)
- Literal pattern:
1, "str", 1+2j, (1, 2),
- As pattern:
a, var
- Wildcard:
_
- Nested patterns:
- Tuple:
(pat1, pat2, pat3), (pat1, *pat2, pat3)
- List:
[pat1, pat2, pat3], [pat1, *pat2, pat3]
- Recogniser:
Cons(pat1, pat2, pat3)
, note that, the functionCons.__match__(<n arg>, value_to_match)
is exact the protocol.
- Tuple:
Case Study : Template-Python
# moshmosh?
# +template-python
@quote
def f(x):
x + 1
x = y + 1
from moshmosh.ast_compat import ast
from astpretty import pprint
stmts = f(ast.Name("a"))
pprint(ast.fix_missing_locations(stmts[0]))
pprint(ast.fix_missing_locations(stmts[1]))
# =>
Expr(
lineno=7,
col_offset=4,
value=BinOp(
lineno=7,
col_offset=4,
left=Name(lineno=7, col_offset=4, id='a', ctx=Load()),
op=Add(),
right=Num(lineno=7, col_offset=8, n=1),
),
)
Assign(
lineno=8,
col_offset=4,
targets=[Name(lineno=8, col_offset=4, id='a', ctx=Store())],
value=BinOp(
lineno=8,
col_offset=8,
left=Name(lineno=8, col_offset=8, id='y', ctx=Load()),
op=Add(),
right=Num(lineno=8, col_offset=12, n=1),
),
)
Acknowledgements
- future-fstrings
- Pattern matching in Python
- older implementations
- search "pattern matching" at Python-ideas.
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