Added basic lambda parser

parser.py

@@ -0,0 +1,65 @@
+import pyparsing as pp
+import tokens
+
+class Parser:
+	"""
+	Macro_def must be on its own line.
+	macro_def  :: var = expr
+
+	var        :: word
+	lambda_fun :: var -> expr
+	call       :: '(' (var | expr) ')' +
+	expr       :: define | var | call | '(' expr ')'
+	"""
+
+	lp = pp.Suppress("(")
+	rp = pp.Suppress(")")
+	func_char = pp.Suppress("->")
+	macro_char = pp.Suppress("=")
+
+	# Simple tokens
+	pp_expr = pp.Forward()
+	pp_name = pp.Word(pp.alphas + "_")
+	pp_name.set_parse_action(tokens.macro.from_parse)
+
+	# Function definitions.
+	# Right associative.
+	#
+	# <var> => <exp>
+	pp_lambda_fun = pp_name + func_char + pp_expr
+	pp_lambda_fun.set_parse_action(tokens.lambda_func.from_parse)
+
+	# Assignment.
+	# Can only be found at the start of a line.
+	#
+	# <var> = <exp>
+	pp_macro_def = pp.line_start() + pp_name + macro_char + pp_expr
+	pp_macro_def.set_parse_action(tokens.macro_expression.from_parse)
+
+	# Function calls.
+	# `tokens.lambda_func.from_parse` handles chained calls.
+	#
+	# <var>(<exp>)
+	# <var>(<exp>)(<exp>)(<exp>)
+	# (<exp>)(<exp>)
+	# (<exp>)(<exp>)(<exp>)(<exp>)
+	pp_call = pp.Forward()
+	pp_call <<= pp_expr[2, ...]
+	pp_call.set_parse_action(tokens.lambda_apply.from_parse)
+
+	pp_expr <<= pp_lambda_fun ^ (lp + pp_expr + rp) ^ pp_name ^ (lp + pp_call + rp)
+	pp_all = pp_expr | pp_macro_def
+
+	@staticmethod
+	def parse_expression(line):
+		return Parser.pp_expr.parse_string(line, parse_all = True)[0]
+
+	@staticmethod
+	def parse_assign(line):
+		return (
+			Parser.pp_macro_def
+		).parse_string(line, parse_all = True)[0]
+
+	@staticmethod
+	def run_tests(lines):
+		return Parser.pp_macro_def.run_tests(lines)