diff --git a/shell/math.h b/shell/math.h
index 96088b4..9f3da7f 100644
--- a/shell/math.h
+++ b/shell/math.h
@@ -9,61 +9,59 @@
 
 /* The math library has just one function:
  *
- *	arith_t arith(const char *expr, int *perrcode, arith_eval_hooks_t *hooks);
+ * arith_t arith(arith_state_t *states, const char *expr);
  *
- *	The first argument is the math string to parse.  All normal expansions must
- *	be done already.  i.e. no dollar symbols should be present.
+ * The expr argument is the math string to parse.  All normal expansions must
+ * be done already.  i.e. no dollar symbols should be present.
  *
- *	The second argument is a semi-detailed error description in case something
- *	goes wrong in the parsing steps.  Currently, those values are (for
- *	compatibility, you should assume all negative values are errors):
- *		 0 - no errors (yay!)
- *		-1 - unspecified problem
- *		-2 - divide by zero
- *		-3 - exponent less than 0
- *		-5 - expression recursion loop detected
+ * The state argument is a pointer to a struct of hooks for your shell (see below),
+ * and a semi-detailed error code. Currently, those values are (for
+ * compatibility, you should assume all negative values are errors):
+ * 0 - no errors (yay!)
+ * -1 - unspecified problem
+ * -2 - divide by zero
+ * -3 - exponent less than 0
+ * -5 - expression recursion loop detected
  *
- *	The third argument is a struct pointer of hooks for your shell (see below).
- *
- *	The function returns the answer to the expression.  So if you called it
- *	with the expression:
- *		"1 + 2 + 3"
- *	You would obviously get back 6.
+ * The function returns the answer to the expression.  So if you called it
+ * with the expression:
+ * "1 + 2 + 3"
+ * you would obviously get back 6.
  */
 
 /* To add support to a shell, you need to implement three functions:
  *
- *	lookupvar() - look up and return the value of a variable
+ * lookupvar() - look up and return the value of a variable
  *
- *		If the shell does:
- *			foo=123
- *		Then the code:
- *			const char *val = lookupvar("foo");
- *		Will result in val pointing to "123"
+ *	If the shell does:
+ *		foo=123
+ *	Then the code:
+ *		const char *val = lookupvar("foo");
+ *	will result in val pointing to "123"
  *
- *	setvar() - set a variable to some value
+ * setvar() - set a variable to some value
  *
- *		If the arithmetic expansion does something like:
- *			$(( i = 1))
- *		Then the math code will make a call like so:
- *			setvar("i", "1", 0);
- *		The storage for the first two parameters are not allocated, so your
- *		shell implementation will most likely need to strdup() them to save.
+ *	If the arithmetic expansion does something like:
+ *		$(( i = 1))
+ *	then the math code will make a call like so:
+ *		setvar("i", "1", 0);
+ *	The storage for the first two parameters are not allocated, so your
+ *	shell implementation will most likely need to strdup() them to save.
  *
- *	endofname() - return the end of a variable name from input
+ * endofname() - return the end of a variable name from input
  *
- *		The arithmetic code does not know about variable naming conventions.
- *		So when it is given an experession, it knows something is not numeric,
- *		but it is up to the shell to dictate what is a valid identifiers.
- *		So when it encounters something like:
- *			$(( some_var + 123 ))
- *		It will make a call like so:
- *			end = endofname("some_var + 123");
- *		So the shell needs to scan the input string and return a pointer to the
- *		first non-identifier string.  In this case, it should return the input
- *		pointer with an offset pointing to the first space.  The typical
- *		implementation will return the offset of first char that does not match
- *		the regex (in C locale): ^[a-zA-Z_][a-zA-Z_0-9]*
+ *	The arithmetic code does not know about variable naming conventions.
+ *	So when it is given an experession, it knows something is not numeric,
+ *	but it is up to the shell to dictate what is a valid identifiers.
+ *	So when it encounters something like:
+ *		$(( some_var + 123 ))
+ *	It will make a call like so:
+ *		end = endofname("some_var + 123");
+ *	So the shell needs to scan the input string and return a pointer to the
+ *	first non-identifier string.  In this case, it should return the input
+ *	pointer with an offset pointing to the first space.  The typical
+ *	implementation will return the offset of first char that does not match
+ *	the regex (in C locale): ^[a-zA-Z_][a-zA-Z_0-9]*
  */
 
 /* To make your life easier when dealing with optional 64bit math support,
@@ -96,13 +94,14 @@
 typedef void        FAST_FUNC (*arith_var_set_t)(const char *name, const char *val);
 //typedef const char* FAST_FUNC (*arith_var_endofname_t)(const char *name);
 
-typedef struct arith_eval_hooks {
+typedef struct arith_state_t {
 	arith_var_lookup_t    lookupvar;
 	arith_var_set_t       setvar;
 //	arith_var_endofname_t endofname;
-} arith_eval_hooks_t;
+	int                   errcode;
+} arith_state_t;
 
-arith_t arith(const char *expr, int *perrcode, arith_eval_hooks_t*);
+arith_t arith(arith_state_t *state, const char *expr);
 
 POP_SAVED_FUNCTION_VISIBILITY