Initialise

ziffers/__init__.py

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+from .parser import *

ziffers/ebnf.py

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+ebnf = r"""
+    expr = (number ws?)* 
+    number = factor additive*
+    additive = ("+"/"-") factor
+    factor = primary multiplicative*
+    multiplicative = ("*" / "/") primary
+    primary = parens / neg / number
+    parens   = "(" number ")"
+    neg = "-" primary 
+    number = ((~"[0-9]"+ "."? ~"[0-9]"*) / ("." ~"[0-9]"+)) (("e"/"E") ("-"/"+") ~"[0-9]"+)?
+    ws        = ~"\s*"
+    lpar      = "("
+    rpar      = ")"
+    lbra      = "["
+    rbra      = "]"
+    lcbra     = "{"
+    rcbra     = "}"
+    lt        = "<"
+    gt        = ">"
+    comma     = ","
+    octup     = "^"
+    octdown   = "_"
+    barsign   = "|"
+    plus = "+"
+    minus = "-"
+    times = "*"
+    div   = "/"
+    emptyline = ws+
+    """

ziffers/parser.py

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+from parsimonious.grammar import Grammar
+from parsimonious.nodes import NodeVisitor
+from .ebnf import ebnf
+
+__all__ = ('ZiffersVisitor', 'parse_expression',)
+
+GRAMMAR = Grammar(ebnf)
+
+class ZiffersVisitor(NodeVisitor):
+    def visit_expr(self, node, visited_children):
+        """ Returns the overall output. """
+        output = {}
+        for child in visited_children:
+            output.update(child[0])
+        return output
+
+    def visit_entry(self, node, visited_children):
+        """ Makes a dict of the section (as key) and the key/value pairs. """
+        key, values = visited_children
+        return {key: dict(values)}
+
+    def visit_section(self, node, visited_children):
+        """ Gets the section name. """
+        _, section, *_ = visited_children
+        return section.text
+
+    def visit_pair(self, node, visited_children):
+        """ Gets each key/value pair, returns a tuple. """
+        key, _, value, *_ = node.children
+        return key.text, value.text
+
+    def generic_visit(self, node, visited_children):
+        """ The generic visit method. """
+        return visited_children or node
+
+def parse_expression(expression: str) -> dict:
+    tree = GRAMMAR.parse(expression)
+    visitor = ZiffersVisitor()
+    return visitor.visit(tree)
+