diff --git a/src/hammer.h b/src/hammer.h
index f09af099b3cc2b484470fe7c2b2e82bdaf7d5be6..95da5e2f6c60d96db04964e6f3e65c573235c64b 100644
--- a/src/hammer.h
+++ b/src/hammer.h
@@ -109,12 +109,16 @@ parse_result_t* parse(const parser_t* parser, const uint8_t* input, size_t lengt
 
 /**
  * Given a string, returns a parser that parses that string value. 
+ * 
+ * Result token type: TT_BYTES
  */
 const parser_t* token(const uint8_t *str, const size_t len);
 
 /**
  * Given a single character, returns a parser that parses that 
  * character. 
+ * 
+ * Result token type: TT_UINT
  */
 const parser_t* ch(const uint8_t c);
 
@@ -122,98 +126,118 @@ const parser_t* ch(const uint8_t c);
  * Given two single-character bounds, lower and upper, returns a parser
  * that parses a single character within the range [lower, upper] 
  * (inclusive). 
+ * 
+ * Result token type: TT_UINT
  */
 const parser_t* range(const uint8_t lower, const uint8_t upper);
 
 /**
  * Returns a parser that parses the specified number of bits. sign == 
  * true if signed, false if unsigned. 
+ *
+ * Result token type: TT_SINT if sign == true, TT_UINT if sign == false
  */
 const parser_t* bits(size_t len, bool sign);
 
 /**
  * Returns a parser that parses a signed 8-byte integer value. 
+ *
+ * Result token type: TT_SINT
  */
 const parser_t* int64();
 
 /**
  * Returns a parser that parses a signed 4-byte integer value. 
+ *
+ * Result token type: TT_SINT
  */
 const parser_t* int32();
 
 /**
  * Returns a parser that parses a signed 2-byte integer value. 
+ *
+ * Result token type: TT_SINT
  */
 const parser_t* int16();
 
 /**
  * Returns a parser that parses a signed 1-byte integer value. 
+ *
+ * Result token type: TT_SINT
  */
 const parser_t* int8();
 
 /**
  * Returns a parser that parses an unsigned 8-byte integer value. 
+ *
+ * Result token type: TT_UINT
  */
 const parser_t* uint64();
 
 /**
  * Returns a parser that parses an unsigned 4-byte integer value. 
+ *
+ * Result token type: TT_UINT
  */
 const parser_t* uint32();
 
 /**
  * Returns a parser that parses an unsigned 2-byte integer value. 
+ *
+ * Result token type: TT_UINT
  */
 const parser_t* uint16();
 
 /**
  * Returns a parser that parses an unsigned 1-byte integer value. 
+ *
+ * Result token type: TT_UINT
  */
 const parser_t* uint8();
 
-/**
- * Returns a parser that parses a double-precision floating-point 
- * value. 
- */
-const parser_t* float64();
-
-/**
- * Returns a parser that parses a single-precision floating-point 
- * value. 
- */
-const parser_t* float32();
-
 /**
  * Given another parser, p, returns a parser that skips any whitespace 
  * and then applies p. 
+ *
+ * Result token type: p's result type
  */
 const parser_t* whitespace(const parser_t* p);
 
 /**
  * Given another parser, p, and a function f, returns a parser that 
  * applies p, then applies f to everything in the AST of p's result. 
+ *
+ * Result token type: any
  */
 const parser_t* action(const parser_t* p, const action_t a);
 
 /**
  * Parse a single character *NOT* in the given charset. 
+ *
+ * Result token type: TT_UINT
  */
 const parser_t* not_in(const uint8_t *charset, int length);
 
 /**
  * A no-argument parser that succeeds if there is no more input to 
  * parse. 
+ *
+ * Result token type: None. The parse_result_t exists but its AST is NULL.
  */
 const parser_t* end_p();
 
 /**
  * This parser always fails. 
+ *
+ * Result token type: NULL. Always.
  */
 const parser_t* nothing_p();
 
 /**
  * Given a null-terminated list of parsers, apply each parser in order.
  * The parse succeeds only if all parsers succeed. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* sequence(const parser_t* p, ...) __attribute__((sentinel));
 
@@ -221,6 +245,8 @@ const parser_t* sequence(const parser_t* p, ...) __attribute__((sentinel));
  * Given an array of parsers, p_array, apply each parser in order. The 
  * first parser to succeed is the result; if no parsers succeed, the 
  * parse fails. 
+ *
+ * Result token type: The type of the first successful parser's result.
  */
 const parser_t* choice(const parser_t* p, ...) __attribute__((sentinel));
 
@@ -229,6 +255,8 @@ const parser_t* choice(const parser_t* p, ...) __attribute__((sentinel));
  * cases: 
  * - if p1 succeeds and p2 fails
  * - if both succeed but p1's result is as long as or shorter than p2's
+ *
+ * Result token type: p1's result type.
  */
 const parser_t* butnot(const parser_t* p1, const parser_t* p2);
 
@@ -237,42 +265,56 @@ const parser_t* butnot(const parser_t* p1, const parser_t* p2);
  * cases:
  * - if p1 succeeds and p2 fails
  * - if both succeed but p2's result is shorter than p1's
+ *
+ * Result token type: p1's result type.
  */
 const parser_t* difference(const parser_t* p1, const parser_t* p2);
 
 /**
  * Given two parsers, p1 and p2, this parser succeeds if *either* p1 or
  * p2 succeed, but not if they both do.
+ *
+ * Result token type: The type of the result of whichever parser succeeded.
  */
 const parser_t* xor(const parser_t* p1, const parser_t* p2);
 
 /**
  * Given a parser, p, this parser succeeds for zero or more repetitions
  * of p. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* many(const parser_t* p);
 
 /**
  * Given a parser, p, this parser succeeds for one or more repetitions 
  * of p. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* many1(const parser_t* p);
 
 /**
  * Given a parser, p, this parser succeeds for exactly N repetitions 
  * of p. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* repeat_n(const parser_t* p, const size_t n);
 
 /**
  * Given a parser, p, this parser succeeds with the value p parsed or 
  * with an empty result. 
+ *
+ * Result token type: If p succeeded, the type of its result; if not, TT_NONE.
  */
 const parser_t* optional(const parser_t* p);
 
 /**
  * Given a parser, p, this parser succeeds if p succeeds, but doesn't 
  * include p's result in the result. 
+ *
+ * Result token type: None. The parse_result_t exists but its AST is NULL.
  */
 const parser_t* ignore(const parser_t* p);
 
@@ -282,31 +324,50 @@ const parser_t* ignore(const parser_t* p);
  * separated by sep.
  * For example, if p is repeat1(range('0','9')) and sep is ch(','), 
  * sepBy(p, sep) will match a comma-separated list of integers. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* sepBy(const parser_t* p, const parser_t* sep);
 
 /**
  * Given a parser, p, and a parser for a separator, sep, this parser matches a list of things that p can parse, separated by sep. Unlike sepBy, this ensures that the result has at least one element.
  * For example, if p is repeat1(range('0','9')) and sep is ch(','), sepBy1(p, sep) will match a comma-separated list of integers. 
+ *
+ * Result token type: TT_SEQUENCE
  */
 const parser_t* sepBy1(const parser_t* p, const parser_t* sep);
 
 /**
  * This parser always returns a zero length match, i.e., empty string. 
+ *
+ * Result token type: None. The parse_result_t exists but its AST is NULL.
  */
 const parser_t* epsilon_p();
 
+/**
+ * This parser applies its first argument to read an unsigned integer
+ * value, then applies its second argument that many times. length 
+ * should parse an unsigned integer value; this is checked at runtime.
+ * Specifically, the token_type of the returned token must be TT_UINT.
+ * In future we might relax this to include TT_USER but don't count on it.
+ *
+ * Result token type: TT_SEQUENCE
+ */
+const parser_t* length_value(const parser_t* length, const parser_t* value);
+
 /**
  * This parser attaches a predicate function, which returns true or 
  * false, to a parser. The function is evaluated over the parser's 
  * result. 
  * The parse only succeeds if the attribute function returns true. 
+ *
+ * Result token type: p's result type if pred succeeded, NULL otherwise.
  */
 const parser_t* attr_bool(const parser_t* p, predicate_t pred);
 
 /**
- * The 'and' parser is a predicate. It asserts that a conditional 
- * syntax is satisfied, but consumes no input. 
+ * The 'and' parser asserts that a conditional syntax is satisfied, 
+ * but doesn't consume that conditional syntax. 
  * This is useful for lookahead. As an example:
  *
  * Suppose you already have a parser, hex_p, that parses numbers in 
@@ -315,14 +376,15 @@ const parser_t* attr_bool(const parser_t* p, predicate_t pred);
  * checks to see whether there is a leading "0x", *does not* consume 
  * the "0x", and then applies hex_p to parse the hex-formatted number.
  *
- * 'and' succeeds if p succeeds, and fails if p fails. Like 'ignore', 
- * 'and' does not attach a result to the AST.
+ * 'and' succeeds if p succeeds, and fails if p fails. 
+ *
+ * Result token type: None. The parse_result_t exists but its AST is NULL.
  */
 const parser_t* and(const parser_t* p);
 
 /**
- * The 'not' parser is a predicate. It asserts that a conditional 
- * syntax is *not* satisfied, and consumes no input.
+ * The 'not' parser asserts that a conditional syntax is *not* 
+ * satisfied, but doesn't consume that conditional syntax.
  * As a somewhat contrived example:
  * 
  * Since 'choice' applies its arguments in order, the following parser:
@@ -335,6 +397,8 @@ const parser_t* and(const parser_t* p);
  *   sequence(ch('a'), choice(sequence(ch('+'), not(ch('+')), NULL), token((const uint8_t*)"++")), ch('b'), NULL)
  * If the input string is "a+b", the first alternative is applied; if 
  * the input string is "a++b", the second alternative is applied.
+ * 
+ * Result token type: None. The parse_result_t exists but its AST is NULL.
  */
 const parser_t* not(const parser_t* p);
 
@@ -343,6 +407,9 @@ const parser_t* not(const parser_t* p);
  * parser.
  * Note that the inner parser gets bound later, with bind_indirect.
  * This can be used to create recursive parsers.
+ *
+ * Result token type: the type of whatever parser is bound to it with
+ * bind_indirect().
  */
 parser_t *indirect();