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#
# spy_parser.py
#
# SPy (Simplified Python) - SPY is a strongly typed, easy to use language inspired by
# features from Python and functional languages like OCaml and SML.
#
# Language definition submitted by Sanil Shah as part of the coursework for
# COMS W4115 - Programming Languages and Translators, at Columbia University,
# New York, NY. Lecturer: Prof. Stephen A. Edwards.
#
# See SPy language definition: https://www.cs.columbia.edu/~sedwards/classes/2016/4115-summer-cvn/lrms/SPY.pdf
#
import sys
import pyparsing as pp
sys.setrecursionlimit(3000)
# pp.ParserElement.enable_packrat()
pp.ParserElement.enable_left_recursion()
pp.ParserElement.set_default_whitespace_chars(" \t")
NL = pp.LineEnd()
TERM = NL | pp.StringEnd()
(
DEF,
LAMBDA,
END,
PRINT,
IF,
ELIF,
ELSE,
HD,
TL,
KEYS,
AND,
OR,
NOT,
TRUE,
FALSE,
KEYS,
) = pp.Keyword.using_each(
"def,lambda,end,print,if,elif,else,hd,tl,keys,and,or,not,true,false,keys".split(",")
)
# general punctuation - can be suppressed, used just as delimiters
LPAR, RPAR, LBRACE, RBRACE, LSQUARE, RSQUARE, COMMA, DOT, COLON = (
pp.Suppress.using_each("(){}[],.:")
)
# operators - can not be suppressed, needed to distinguish among operations at same precedence level
ADD, SUB, DIV, MUL, MOD, CONCAT = pp.Literal.using_each("+-/*%^")
LT, GT, LE, GE, EQ, NE = pp.Literal.using_each("< > <= >= == !=".split())
MINUS = SUB
LIST_CONS, LIST_APP = pp.Literal.using_each(":: @".split())
DICT_SET = pp.Literal("<-")
integer = pp.Regex(r"0|[1-9][0-9]*").set_name("integer")
float_ = pp.Regex(r"(0|[1-9]\d*)\.\d*").set_name("float")
string = pp.Regex(r'"([^\\"]|\\[\\nrt])*"').set_name("string")
identifier = pp.Regex(r"[a-z][a-zA-Z0-9_]*").set_name("identifier")
bool_literal = TRUE | FALSE
list_literal = pp.Forward()
dict_literal = pp.Forward()
string_expr = pp.infix_notation(
string,
[
(CONCAT, 2, pp.OpAssoc.LEFT),
],
).set_name("string_expr")
arith_expr = pp.infix_notation(
(float_ | integer).set_name("arith_operand"),
[
(MINUS().set_name("unary_minus"), 1, pp.OpAssoc.RIGHT),
((MUL | DIV | MOD).set_name("mul_op"), 2, pp.OpAssoc.LEFT),
((ADD | SUB).set_name("add_op"), 2, pp.OpAssoc.LEFT),
],
).set_name("arith_expr")
expr = pp.Forward().set_name("expr")
conditional_expr = pp.infix_notation(
expr,
[((LE | GE | LT | GT | EQ | NE).set_name("comparison_op"), 2, pp.OpAssoc.LEFT)],
).set_name("conditional_expr")
bool_expr = pp.infix_notation(
(bool_literal | conditional_expr).set_name("bool_operand"),
[
(NOT, 1, pp.OpAssoc.RIGHT),
(AND, 2, pp.OpAssoc.LEFT),
(OR, 2, pp.OpAssoc.LEFT),
],
).set_name("bool_expr")
expr <<= string_expr | bool_expr | arith_expr
list_literal <<= LSQUARE + pp.DelimitedList(expr)[0, 1] + RSQUARE
dict_literal <<= LBRACE + pp.DelimitedList(expr)[0, 1] + RBRACE
statement = pp.Forward().set_name("statement")
block = (statement + NL)[1, ...].set_name("block")
arg_list = pp.DelimitedList(identifier)[0, 1]
lambda_def = LAMBDA + LPAR + arg_list("args") + RPAR + COLON + expr
function_def = pp.Group(
DEF
+ identifier("name")
+ LPAR
+ arg_list("args")
+ RPAR
+ COLON
+ NL
+ block("body")
+ END
)
lhs = identifier
assignment_stmt = lhs("lhs") + "=" + expr("rhs")
if_stmt = pp.Group(
IF
+ conditional_expr("condition")
+ COLON
+ NL
+ block("if_block")
+ NL
+ pp.Group(ELIF + conditional_expr("condition") + COLON + NL + block + NL)[0, ...](
"elif_blocks"
)
+ ELSE
+ COLON
+ NL
+ block("else_block")
)
dict_set_stmt = pp.Group(
identifier("dest") + LSQUARE + expr("key") + RSQUARE + DICT_SET + expr("rhs")
)
statement <<= pp.Group(
(if_stmt | function_def | assignment_stmt | dict_set_stmt) + TERM
)
spy_program = statement[1, ...].set_name("program")
pp.autoname_elements()
if __name__ == "__main__":
import contextlib
with contextlib.suppress(Exception):
spy_program.create_diagram("spy_grammar.html")
statement.run_tests(
"""\
a = 100
b = 0.100
c = true and false
d["blah"] <- 1000
"""
)
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