Update CODING_STYLE.md

CODING_STYLE.md

@@ -3,20 +3,22 @@
 GOLDEN RULE: Follow the style of the existing code when you make changes.
 
 a. Use tabs for leading indentation
-- tab stops are every 4 characters.
+- tab stops are every 4 characters (only relevant for line length).
 - One indentation level -> exactly one byte (i.e. a tab character) in the source file.
-- If you have run-on lines, indent as you would for a block.
 b. Line widths:
-- Don't worry about having lines of code > 80-char wide.
+- Lines should be at most 99 characters wide to make diff views readable and reduce merge conflicts.
 - Lines of comments should be formatted according to ease of viewing, but simplicity is to be preferred over beauty.
-c. Don't use braces for condition-body one-liners.
+c. Single-statement blocks should not have braces, unless required for clarity.
 d. Never place condition bodies on same line as condition.
-e. Space between first paren and keyword, but *not* following first paren or preceding final paren.
-f. No spaces when fewer than intra-expression three parens together; when three or more, space according to clarity.
-g. No spaces for subscripting or unary operators.
-h. No space before ':' but one after it, except in the ternary operator: one on both sides.
-i. Space all other operators.
-j. Braces, when used, always have their own lines and are at same indentation level as "parent" scope.
+e. Space between keyword and opening parenthesis, but not following opening parenthesis or before final parenthesis.
+f. No spaces for unary operators, `->` or `.`.
+g. No space before ':' but one after it, except in the ternary operator: one on both sides.
+h. Add spaces around all other operators.
+i. Braces, when used, always have their own lines and are at same indentation level as "parent" scope.
+j. If lines are broken, a list of elements enclosed with parentheses (of any kind) and separated by a
+   separator (of any kind) are formatted such that there is exactly one element per line, followed by
+   the separator, the opening parenthesis is on the first line, followed by a line break and the closing
+   parenthesis is on a line of its own (unindented). See example below.
 
 (WRONG)
 if( a==b[ i ] ) { printf ("Hello\n"); }
@@ -25,6 +27,7 @@ foo->bar(someLongVariableName,
          anotherLongVariableName,
          anotherLongVariableName,
          anotherLongVariableName);
+cout << "some very long string that contains completely irrelevant text that talks about this and that and contains the words \"lorem\" and \"ipsum\"" << endl;
 
 (RIGHT)
 if (a == b[i])
@@ -36,6 +39,11 @@ foo->bar(
     anotherLongVariableName,
     anotherLongVariableName
 );
+cout <<
+    "some very long string that contains completely irrelevant " <<
+    "text that talks about this and that and contains the words " <<
+    "\"lorem\" and \"ipsum\"" <<
+    endl;
 
 
 
@@ -43,7 +51,8 @@ foo->bar(
 
 a. No "using namespace" declarations in header files.
 b. All symbols should be declared in a namespace except for final applications.
-c. Preprocessor symbols should be prefixed with the namespace in all-caps and an underscore.
+c. Use anonymous namespaces for helpers whose scope is a cpp file only.
+d. Preprocessor symbols should be prefixed with the namespace in all-caps and an underscore.
 
 (WRONG)
 #include <cassert>
@@ -90,16 +99,16 @@ All other entities' first alpha is lower case.
 a. Leading underscore "_" to parameter names.
 - Exception: "o_parameterName" when it is used exclusively for output. See 6(f).
 - Exception: "io_parameterName" when it is used for both input and output. See 6(f).
-b. Leading "c_" to const variables (unless part of an external API).
-c. Leading "g_" to global (non-const) variables.
-d. Leading "s_" to static (non-const, non-global) variables.
+b. Leading "g_" to global (non-const) variables.
+c. Leading "s_" to static (non-const, non-global) variables.
 
 
 
-5. Error reporting:
-
-- Prefer exception to bool/int return type.
+5. Assertions:
 
+- use `solAssert` and `solUnimplementedAssert` generously to check assumptions
+  that span across different parts of the code base, for example before dereferencing
+  a pointer.
 
 
 6. Declarations:
@@ -108,15 +117,14 @@ a. {Typename} + {qualifiers} + {name}.
 b. Only one per line.
 c. Associate */& with type, not variable (at ends with parser, but more readable, and safe if in conjunction with (b)).
 d. Favour declarations close to use; don't habitually declare at top of scope ala C.
-e. Always pass non-trivial parameters with a const& suffix.
-f. If a function returns multiple values, use std::tuple (std::pair acceptable). Prefer not using */& arguments, except where efficiency requires.
-g. Never use a macro where adequate non-preprocessor C++ can be written.
-h. Make use of auto whenever type is clear or unimportant:
-- Always avoid doubly-stating the type.
-- Use to avoid vast and unimportant type declarations.
-- However, avoid using auto where type is not immediately obvious from the context, and especially not for arithmetic expressions.
-i. Don't pass bools: prefer enumerations instead.
-j. Prefer enum class to straight enum.
+e. Pass non-trivial parameters as const reference, unless the data is to be copied into the function, then either pass by const reference or by value and use std::move.
+f. If a function returns multiple values, use std::tuple (std::pair acceptable) or better introduce a struct type. Do not use */& arguments.
+g. Use parameters of pointer type only if ``nullptr`` is a valid argument, use references otherwise. Often, ``boost::optional`` is better suited than a raw pointer.
+h. Never use a macro where adequate non-preprocessor C++ can be written.
+i. Only use ``auto`` if the type is very long and rather irrelevant.
+j. Do not pass bools: prefer enumerations instead.
+k. Prefer enum class to straight enum.
+l. Always initialize POD variables, even if their value is overwritten later.
 
 
 (WRONG)
@@ -134,13 +142,18 @@ enum class Accuracy
 	Approximate,
 	Exact
 };
+struct MeanSigma
+{
+	float mean;
+	float standardDeviation;
+};
 double const d = 0;
 int i;
 int j;
 char* s;
-std::tuple<float, float> meanAndSigma(std::vector<float> const& _v, Accuracy _a);
-auto x = dynamic_cast<Derived*>(base);
-for (auto i = x.begin(); i != x.end(); ++i) {}
+MeanAndSigma ms meanAndSigma(std::vector<float> const& _v, Accuracy _a);
+Derived* x = dynamic_cast<Derived*>(base);
+for (auto i = x->begin(); i != x->end(); ++i) {}
 
 
 7. Structs & classes
@@ -169,17 +182,10 @@ f. For a property 'foo'
 
 9. Naming
 
-a. Collection conventions:
-- -s means std::vector e.g. using MyTypes = std::vector<MyType>
-- -Set means std::set e.g. using MyTypeSet = std::set<MyType>
-- -Hash means std::unordered_set e.g. using MyTypeHash = std::unordered_set<MyType>
-b. Class conventions:
-- -Face means the interface of some shared concept. (e.g. FooFace might be a pure virtual class.)
-c. Avoid unpronouncable names;
-- If you need to shorten a name favour a pronouncable slice of the original to a scattered set of consonants.
-- e.g. Manager shortens to Man rather than Mgr.
-d. Avoid prefixes of initials (e.g. DON'T use IMyInterface, CMyImplementation)
-e. Find short, memorable & (at least semi-) descriptive names for commonly used classes or name-fragments.
+a. Avoid unpronouncable names
+b. Names should be shortened only if they are extremely common, but shortening should be generally avoided
+c. Avoid prefixes of initials (e.g. do not use IMyInterface, CMyImplementation)
+c. Find short, memorable & (at least semi-) descriptive names for commonly used classes or name-fragments.
 - A dictionary and thesaurus are your friends.
 - Spell correctly.
 - Think carefully about the class's purpose.
@@ -194,8 +200,9 @@ a. Prefer 'using' to 'typedef'. e.g. using ints = std::vector<int>; rather than
 b. Generally avoid shortening a standard form that already includes all important information:
 - e.g. stick to shared_ptr<X> rather than shortening to ptr<X>.
 c. Where there are exceptions to this (due to excessive use and clear meaning), note the change prominently and use it consistently.
-- e.g. using Guard = std::lock_guard<std::mutex>; ///< Guard is used throughout the codebase since it's clear in meaning and used commonly. 
+- e.g. using Guard = std::lock_guard<std::mutex>; ///< Guard is used throughout the codebase since it is clear in meaning and used commonly. 
 d. In general expressions should be roughly as important/semantically meaningful as the space they occupy.
+e. Avoid introducing aliases for types unless they are very complicated. Consider the number of items a brain can keep track of at the same time.
 
 
 
@@ -207,40 +214,41 @@ b. Document the interface, not the implementation.
 - Comment in terms of the method properties and intended alteration to class state (or what aspects of the state it reports).
 - Be careful to scrutinise documentation that extends only to intended purpose and usage.
 - Reject documentation that is simply an English transaction of the implementation.
-
+c. Avoid in-code comments. Instead, try to extract blocks of functionality into functions. This often already eliminates the need for an in-code comment.
 
 
 12. Include Headers
 
-Includes should go in increasing order of generality (libethereum -> libethcore -> libdevcrypto -> libdevcore -> boost -> STL).  For example:
+Includes should go in increasing order of generality (libsolidity -> libevmasm -> libdevcore -> boost -> STL).
+The corresponding .h file should be the first include in the respective .cpp file.
+Insert empty lines between blocks of include files.
+
+Example:
+
+```
+#include <libsolidity/codegen/ExpressionCompiler.h>
+
+#include <libsolidity/ast/AST.h>
+#include <libsolidity/codegen/CompilerContext.h>
+#include <libsolidity/codegen/CompilerUtils.h>
+#include <libsolidity/codegen/LValue.h>
+
+#include <libevmasm/GasMeter.h>
 
-#include <libethereum/Defaults.h>
-#include <libdevcrypto/SHA3.h>
-#include <libdevcore/Log.h>
-#include <libdevcore/Exceptions.h>
-#include <libdevcore/CommonData.h>
 #include <libdevcore/Common.h>
-#include <boost/filesystem.hpp>
-#include <string>
+#include <libdevcore/SHA3.h>
+
+#include <boost/range/adaptor/reversed.hpp>
+#include <boost/algorithm/string/replace.hpp>
+
+#include <utility>
+#include <numeric>
+```
 
 See http://stackoverflow.com/questions/614302/c-header-order/614333#614333 for the reason: this makes it easier to find missing includes in header files.
 
 
-
-13. Logging
-
-Logging should be performed at appropriate verbosities depending on the logging message.
-The more likely a message is to repeat (and thus cause noise) the higher in verbosity it should be.
-Some rules to keep in mind:
-
- - Verbosity == 0 -> Reserved for important stuff that users must see and can understand.
- - Verbosity == 1 -> Reserved for stuff that users don't need to see but can understand.
- - Verbosity >= 2 -> Anything that is or might be displayed more than once every minute
- - Verbosity >= 3 -> Anything that only a developer would understand
- - Verbosity >= 4 -> Anything that is low-level (e.g. peer disconnects, timers being cancelled)
-
-
-14. Recommended reading
+13. Recommended reading
 
 Herb Sutter and Bjarne Stroustrup
 - "C++ Core Guidelines" (https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md)