3.2. Parser Module

3.2.1. Lexer Class

class aggregate.parser.UnderwritingLexer

Implements the Lexer for the agg language.

static preprocess(program)

Separate preprocessor step, allowing it to be called separately. Preprocessing involves six steps:

1. Remove // comments, through end of line

2. Remove n in [ ] (vectors) that appear from using f'{np.linspace(...)}'

3. Backslash (line continuation) mapped to space

4. nt is replaced with space, supporting the tabbed indented Portfolio layout

5. Split on newlines

Parameters:

program

Returns:

3.2.2. Parser Class

class aggregate.parser.UnderwritingParser(safe_lookup_function, debug=False)

Implements the Parser for the agg language.

Here are testers for the math expressions:

from aggregate import build
for t in ['-123', '-2%', '45%', '1e-3%', 'inf', '-inf', 'exp(1)', 'exp(1/2)', 'exp(-1)', '-1/8',
          'exp(10)/exp(3**2/2)', '2**10', '50/exp(.3**2/2)', '1/exp(1.9**2 / 2)']:
    a = build(t)
    print(a.name)
    assert float(a.name) == eval(t.replace('%', '/100').replace('exp', 'np.exp').replace('inf', 'np.inf'))

To test on the test_suite:

df = build.run_test_suite()
assert len(df.query('error != 0')) == 0

static enhance_debugfile(f_out='')

Put links in the parser.out debug file, if DEBUGFILE != ‘’.

Parameters:

f_out – Path or filename of output. If “” then DEBUGFILE.html used.

Returns:

error(p)

Default error handling function. This may be subclassed.

3.2.3. Remaining Functions

3.2.3.1. Aggregate Lexer and Parser.

To debug in a repl use the following code:

from aggregate.parser import UnderwritingLexer, UnderwritingParser

lexer = UnderwritingLexer() parser = UnderwritingParser(lambda x: x, debug=True)

while True:

try:

text = input(“>> “) if not text:

continue

except (EOFError, KeyboardInterrupt):

break

try:

if text == ‘x’:

break

tokens = list(lexer.tokenize(text)) print(“Tokens:”) for tok in tokens:

print(f” {tok.type:<10} {tok.value!r}”)

result = parser.parse(iter(tokens)) print(“Parsed:”) print(result)

except Exception as e:

print(“Error:”, e)

aggregate.parser.grammar(add_to_doc=False, save_to_fn='')

Write the grammar at the top of the file as a docstring

To work with multi-rules enter them on one line, like so:

@_('builtin_agg PLUS expr', 'builtin_agg MINUS expr')

Parameters:

• add_to_doc – add the grammar to the docstring

• save_to_fn – save the grammar to a file