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symbol_read.py
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symbol_read.py
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#based on tokenization rules in https://golang.org/ref/spec
#we only tokenize keywords and operators. identifiers and literals are treated character by character
import string
keywords = ['break','default','func','interface','select',
'case','defer','go','map','struct',
'chan','else','goto','package','switch',
'const','fallthrough','if','range','type',
'continue','for','import','return','var'
]
operators = ['+','&','+=','&=','&&','==','!=','(',')',
'-','|','-=','|=','||','<','<=','[',']',
'*','^','*=','^=','<-','>','>=','{','}',
'/','<<','/=','<<=','++','=',':=',',',';',
'%','>>','%=','>>=','--','!','...','.',':',
'&^','&^=']
op_chars = set([x for y in operators for x in operators])
def read_symbols(preprocessed_characters):
"""
a generator function
reads terminal symbols for go's EBNF grammar
yields tuples (symbol, line_number, column_number)
the line_number and column_number corresponds with the position of
the character in the original file
if there is no more symbols to read, yield (None, line_number, column_number)
"""
charbuffer = []
token_type_candidate = '' #candidates:, 'ki' (keywords or identifier),
# 'id' (surely identifier), 'op' (operator),
# '"' (string with \" delim), "'" (string with \' delim) '' (other)
count_string_backslash = 0
prev_isspace=False
for c, l, col in preprocessed_characters:
if token_type_candidate is 'ki':
if c in string.ascii_letters:
charbuffer = charbuffer + [(c,col)]
else:
if c not in string.digits+'_' and to_keyword(charbuffer) in keywords:
yield to_keyword(charbuffer), l, charbuffer[0][1], prev_isspace
charbuffer = []
else:
yield from flush_characters(charbuffer, l, prev_isspace)
charbuffer = []
prev_isspace = c.isspace()
if c.isspace():
token_type_candidate = ''
prev_isspace=True
elif c in string.digits+'_':
token_type_candidate = 'id'
yield c, l, col, prev_isspace
elif c in op_chars:
token_type_candidate = 'op'
charbuffer = charbuffer+[(c,col)]
elif c in ['"',"'","`"]:
yield c, l, col, prev_isspace
token_type_candidate = c
else:
token_type_candidate = ''
yield c, l, col, prev_isspace
elif token_type_candidate is 'id':
if c in string.ascii_letters + string.digits+'_':
yield c, l, col, prev_isspace
elif c.isspace():
token_type_candidate=''
elif c in op_chars:
token_type_candidate = 'op'
charbuffer = charbuffer+[(c,col)]
elif c in ['"',"'","`"]:
yield c, l, col, prev_isspace
token_type_candidate = c
else:
token_type_candidate = ''
yield c, l, col, prev_isspace
elif token_type_candidate is 'op':
if c in op_chars:
charbuffer = charbuffer+[(c,col)]
else:
yield from yield_op(charbuffer, l, prev_isspace)
charbuffer = []
if c.isspace():
token_type_candidate = ''
elif c in string.ascii_letters:
charbuffer = charbuffer+[(c,col)]
token_type_candidate = 'ki'
elif c in '_':
yield c, l, col, prev_isspace
token_type_candidate = 'id'
elif c in ['"',"'","`"]:
yield c, l, col, prev_isspace
token_type_candidate = c
else:
yield c, l, col, prev_isspace
token_type_candidate = ''
elif token_type_candidate in ['"',"'","`"]:
if c is token_type_candidate:
if count_string_backslash % 2 == 0:
token_type_candidate = ''
if c is '\\':
count_string_backslash = count_string_backslash + 1
else:
count_string_backslash = 0
yield c, l, col, prev_isspace
elif token_type_candidate is '':
if c in string.ascii_letters:
charbuffer = charbuffer+[(c,col)]
token_type_candidate = 'ki'
elif c in op_chars:
charbuffer = charbuffer+[(c,col)]
token_type_candidate = 'op'
elif c is '_':
yield c, l, col, prev_isspace
elif c in ['"',"'","`"]:
yield c, l, col, prev_isspace
token_type_candidate = c
elif not c.isspace():
yield c, l, col, prev_isspace
if len(charbuffer)==0:
prev_isspace = c.isspace()
yield ';',"last","last",False
def flush_characters(charbuffer,l,prev_isspace):
if len(charbuffer)>0:
c, col = charbuffer.pop(0)
yield c, l, col, prev_isspace
for c, col in charbuffer:
yield c, l, col, False
def to_keyword(charbuffer):
return ''.join([c for c,col in charbuffer])
def yield_op(charbuffer, l, prev_isspace):
opchunkstr = to_keyword(charbuffer)
matched_ops = [x for x in operators if x in opchunkstr]
longest_op = max(matched_ops, key=lambda s: len(s))
remainder_strs = opchunkstr.split(longest_op)
#recursion
pos = 0
for i in range(len(remainder_strs)-1):
if remainder_strs[i] is not '':
yield from yield_op(charbuffer[pos:pos+len(remainder_strs[i])], l, prev_isspace and pos==0)
pos = pos + len(remainder_strs[i])
yield longest_op, l, charbuffer[pos][1], prev_isspace and pos==0
pos = pos + len(longest_op)
i = len(remainder_strs)-1
if remainder_strs[i] is not '':
yield from yield_op(charbuffer[pos:pos+len(remainder_strs[i])], l, prev_isspace and pos==0)
pos = pos + len(remainder_strs[i])
if __name__ =='__main__':
import sys
import preprocess
if len(sys.argv) != 2:
print("to test: symbol_read.py <inputfile>")
sys.exit()
with open(sys.argv[1]) as file:
preprocess_generator = preprocess.preprocess(file)
symbol_generator = read_symbols(preprocess_generator)
prev_line_number = 1
for symbol,line_number,col_number,prev_isspace in symbol_generator:
if line_number!='last':
for i in range(prev_line_number,line_number):
print('')
if prev_isspace:
print('<space>',end='')
print(symbol,end='|')
prev_line_number = line_number