STYLE: example for trailing comma & add includes guideline

STYLE

@@ -1,6 +1,7 @@
-- Braces are mandatory for all control flow
+0. Braces are mandatory for all control flow, as it improves the visibility of
-- Nested indentation should be kept to a minimum
+   scope.
-- Empty lines should be placed between different kinds of statements:
+1. Nested indentation should be kept to a minimum.
+2. Empty lines should be placed between different kinds of statements:
 
 	int t;
 
@@ -20,14 +21,14 @@ io->rec   += (t > 0 && io->bufuse == 0);
 
 	return io;
 
-- Cases in switch statements and matches in match statements should be indented
+3. Cases in switch statements and matches in match statements should be indented
    one level
-- In C, spaces should be placed in control flow statements after the keyword and
+4. In C, spaces should be placed in control flow statements after the keyword
-  before the opening brace:
+   and before the opening brace:
 
 	for (i = 2; i < argc; ++i) {
 
-- If a function, a C control flow statement, or a Rust macro has arguments that
+5. If a function, a C control flow statement, or a Rust macro has arguments that
    cause the statement to be broken into multiple lines, this should be done by
    placing the arguments on a new line inside the parentheses: 
 
@@ -36,19 +37,30 @@ let usage = format!(
 		argv[0],
 	);
 
-- If Rust function arguments or fields are on their own lines, they should
+6. If Rust function arguments or fields are on their own lines, they should
-  always have a trailing comma.
+   always have a trailing comma:
 
-- If text is on the same line as a brace, spaces should be placed after an
+	return Err(EvaluationError {
+		message: format!("{}: Invalid token", i),
+		code: EX_DATAERR,
+	})
+
+7. If text is on the same line as a brace, spaces should be placed after an
    opening curly brace and before a closing one:
 
 	use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
 
-- If a control flow statement is short enough to be easily understood in a
+8. If a control flow statement is short enough to be easily understood in a
    glance, it may be placed on a single line:
 
 	if (!argc < 0) { usage(program_name); }
 
+9. In C, note everything you use from a library in a comment subsequent to its
+   #include statement:
+
+	#include <unistd.h> /* close(2), getopt(3), lseek(2), read(2), write(2),
+                         * optarg, optind, STDIN_FILENO, STDOUT_FILENO */
+
 --
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