def parse(string):
'''
Parses a DSL for railroad diagrams,
based on significant whitespace.
Each command must be on its own line,
and is written like "Sequence:\n".
Children are indented on following lines.
Some commands have non-child arguments;
these are put on the same line as the command name,
like:
Choice: 0
Terminal: foo
Terminal: bar
'''
import re
lines = string.splitlines()
# Strip off any common initial whitespace from lines.
initialIndent = re.match(r"(\s*)", lines[0]).group(1)
for i, line in enumerate(lines):
if line.startswith(initialIndent):
lines[i] = line[len(initialIndent):]
else:
die(
"Inconsistent indentation: line {0} is indented less than the first line.",
i)
return rr.Diagram()
# Determine subsequent indentation
for line in lines:
match = re.match(r"(\s+)", line)
if match:
indentText = match.group(1)
break
else:
indentText = "\t"
# Turn lines into tree
lastIndent = 0
tree = {"command": "Diagram", "prelude": "", "children": []}
activeCommands = {"0": tree}
for i, line in enumerate(lines):
indent = 0
while line.startswith(indentText):
indent += 1
line = line[len(indentText):]
if indent > lastIndent + 1:
die(
"Line {0} jumps more than 1 indent level from the previous line:\n{1}",
i, line.strip())
return rr.Diagram()
lastIndent = indent
match = re.match(r"\s*([\w]+)\s*:\s*(.*)", line)
if not match:
die(
"Line {0} doesn't match the grammar 'Command: optional-prelude'. Got:\n{1}",
i, line.strip())
return rr.Diagram()
command = match.group(1)
prelude = match.group(2).strip()
node = {
"command": command,
"prelude": prelude,
"children": [],
"line": i
}
activeCommands[str(indent)]['children'].append(node)
activeCommands[str(indent + 1)] = node
return _createDiagram(**tree)
def _createDiagram(command, prelude, children, line=-1):
'''
From a tree of commands,
create an actual Diagram class.
Each command must be {command, prelude, children}
'''
if command == "Diagram":
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.Diagram(*children)
elif command in ("T", "Terminal"):
if children:
return die("Line {0} - Terminal commands cannot have children.",
line)
return rr.Terminal(prelude)
elif command in ("N", "NonTerminal"):
if children:
return die("Line {0} - NonTerminal commands cannot have children.",
line)
return rr.NonTerminal(prelude)
elif command in ("C", "Comment"):
if children:
return die("Line {0} - Comment commands cannot have children.",
line)
return rr.Comment(prelude)
elif command in ("S", "Skip"):
if children:
return die("Line {0} - Skip commands cannot have children.", line)
if prelude:
return die("Line {0} - Skip commands cannot have preludes.", line)
return rr.Skip()
elif command in ("And", "Seq", "Sequence"):
if prelude:
return die("Line {0} - Sequence commands cannot have preludes.",
line)
if not children:
return die("Line {0} - Sequence commands need at least one child.",
line)
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.Sequence(*children)
elif command in ("Or", "Choice"):
if prelude == "":
default = 0
else:
try:
default = int(prelude)
except:
die("Line {0} - Choice preludes must be an integer. Got:\n{1}",
line, prelude)
default = 0
if not children:
return die("Line {0} - Choice commands need at least one child.",
line)
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.Choice(default, *children)
elif command in ("Opt", "Optional"):
if prelude not in ("", "skip"):
return die(
"Line {0} - Optional preludes must be nothing or 'skip'. Got:\n{1}",
line, prelude)
if len(children) != 1:
return die("Line {0} - Optional commands need exactly one child.",
line)
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.Optional(*children, skip=(prelude == "skip"))
elif command in ("Plus", "OneOrMore"):
if prelude:
return die("Line {0} - OneOrMore commands cannot have preludes.",
line)
if 0 == len(children) > 2:
return die(
"Line {0} - OneOrMore commands must have one or two children.",
line)
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.OneOrMore(*children)
elif command in ("Star", "ZeroOrMore"):
if prelude:
return die("Line {0} - ZeroOrMore commands cannot have preludes.",
line)
if 0 == len(children) > 2:
return die(
"Line {0} - ZeroOrMore commands must have one or two children.",
line)
children = filter(None,
[_createDiagram(**child) for child in children])
return rr.ZeroOrMore(*children)
else:
return die("Line {0} - Unknown command '{1}'.", line, command)
def parse(string):
'''
Parses a DSL for railroad diagrams,
based on significant whitespace.
Each command must be on its own line,
and is written like "Sequence:\n".
Children are indented on following lines.
Some commands have non-child arguments;
for block commands they are put on the same line, after the :,
for text commands they are put on the same line *before* the :,
like:
Choice: 0
Terminal: foo
Terminal raw: bar
'''
import re
lines = string.splitlines()
# Strip off any common initial whitespace from lines.
initialIndent = re.match(r"(\s*)", lines[0]).group(1)
for i, line in enumerate(lines):
if line.startswith(initialIndent):
lines[i] = line[len(initialIndent):]
else:
die(
"Inconsistent indentation: line {0} is indented less than the first line.",
i)
return rr.Diagram()
# Determine subsequent indentation
for line in lines:
match = re.match(r"(\s+)", line)
if match:
indentText = match.group(1)
break
else:
indentText = "\t"
# Turn lines into tree
lastIndent = 0
tree = {"command": "Diagram", "prelude": "", "children": []}
activeCommands = {"0": tree}
blockNames = "And|Seq|Sequence|Stack|Or|Choice|Opt|Optional|Plus|OneOrMore|Star|ZeroOrMore"
textNames = "T|Terminal|N|NonTerminal|C|Comment|S|Skip"
for i, line in enumerate(lines):
indent = 0
while line.startswith(indentText):
indent += 1
line = line[len(indentText):]
if indent > lastIndent + 1:
die(
"Line {0} jumps more than 1 indent level from the previous line:\n{1}",
i, line.strip())
return rr.Diagram()
lastIndent = indent
if re.match(r"\s*({0})\W".format(blockNames), line):
match = re.match(r"\s*(\w+)\s*:\s*(.*)", line)
if not match:
die(
"Line {0} doesn't match the grammar 'Command: optional-prelude'. Got:\n{1}",
i, line.strip())
return rr.Diagram()
command = match.group(1)
prelude = match.group(2).strip()
node = {
"command": command,
"prelude": prelude,
"children": [],
"line": i
}
elif re.match(r"\s*({0})\W".format(textNames), line):
match = re.match(r"\s*(\w+)(\s[\w\s]+)?:\s*(.*)", line)
if not match:
die(
"Line {0} doesn't match the grammar 'Command [optional prelude]: text'. Got:\n{1},",
i, line.strip())
return rr.Diagram()
command = match.group(1)
if match.group(2):
prelude = match.group(2).strip()
else:
prelude = ""
text = match.group(3).strip()
node = {
"command": command,
"prelude": prelude,
"text": text,
"children": [],
"line": i
}
activeCommands[str(indent)]['children'].append(node)
activeCommands[str(indent + 1)] = node
return _createDiagram(**tree)
