Add documenting comments to spanparsing.h

Author: sipa

src/util/spanparsing.h

@@ -12,16 +12,37 @@
 
 namespace spanparsing {
 
-/** Parse a constant. If successful, sp is updated to skip the constant and return true. */
+/** Parse a constant.
+ *
+ * If sp's initial part matches str, sp is updated to skip that part, and true is returned.
+ * Otherwise sp is unmodified and false is returned.
+ */
 bool Const(const std::string& str, Span<const char>& sp);
 
-/** Parse a function call. If successful, sp is updated to be the function's argument(s). */
+/** Parse a function call.
+ *
+ * If sp's initial part matches str + "(", and sp ends with ")", sp is updated to be the
+ * section between the braces, and true is returned. Otherwise sp is unmodified and false
+ * is returned.
+ */
 bool Func(const std::string& str, Span<const char>& sp);
 
-/** Return the expression that sp begins with, and update sp to skip it. */
+/** Extract the expression that sp begins with.
+ *
+ * This function will return the initial part of sp, up to (but not including) the first
+ * comma or closing brace, skipping ones that are surrounded by braces. So for example,
+ * for "foo(bar(1),2),3" the initial part "foo(bar(1),2)" will be returned. sp will be
+ * updated to skip the initial part that is returned.
+ */
 Span<const char> Expr(Span<const char>& sp);
 
-/** Split a string on every instance of sep, returning a vector. */
+/** Split a string on every instance of sep, returning a vector.
+ *
+ * If sep does not occur in sp, a singleton with the entirety of sp is returned.
+ *
+ * Note that this function does not care about braces, so splitting
+ * "foo(bar(1),2),3) on ',' will return {"foo(bar(1)", "2)", "3)"}.
+ */
 std::vector<Span<const char>> Split(const Span<const char>& sp, char sep);
 
 } // namespace spanparsing