underwriter: start new argument parser

2 files changed, 36 insertions, 0 deletions

diff --git a/example/natargs.md b/example/natargs.md
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+++ b/example/natargs.md
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+Natural arguments are those like git commands `git commit`, `git stash`,
+etc. They are "natural" since they are arranged like an english sentence.
diff --git a/example/natargs_python_impl.md b/example/natargs_python_impl.md
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+++ b/example/natargs_python_impl.md
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+The arguments are stored as a trie using python dictonaries.  Each node
+is a class consisting of two functions and a dict representing a subtree.
+
+One function is a check on the length of the arguments, and the other
+is the function executed on the list of arguments.
+
+pseudocode
+----------
+
+```
+def addargs(dict, h::[], chk, f):
+	if dict[h] exists:
+		throw exception
+	dict[h].chk = chk
+	dict[h].f = f
+	dict[h].subtree = {}
+def addargs(dict, h::t, chk, f):
+	if dict[h] does not exist:
+		dict[h].chk = None
+		dict[h].f = None
+	dict[h].subtree = addargs(dict[h].subtree, t, chk, f)
+
+def execargs(dict, h::t):
+	if dict[h] exists:
+		f,args = execargs(dict[h].subtree, t)
+		if f,args is None,None:
+			if not dict[h].chk(t):
+				return None,None
+			return dict[h].f,t
+		else:
+			return f,args
+	else:
+		return None,None
+```