tacticalmelonfarmer/cxl

A C++17 metaprogramming library. Strings, Parsing, Typelists, Aggregate to Tuple conversions and Constant integral literals

Constant eXpression Library (abbreviated cxl)

Fundamental Utilities

include/cxl/utility.hpp contains basic template types and functions that are used across the whole library, such as cxl::index_t which is used in place of size_t and as indices, it should be a signed integer type capable of holding relatively large values, it is signed to allow negative indices. anything that requires a huge unsigned integer as an index value should probably not be done at compile-time. cxl::select_t<N, Types...> selects the Nth type in Types.... cxl::index_range<Indices...> holds a parameter pack of cxl::index_t, and provides some methods:

• .size()
  • returns a std::integral_constant<index_t, sizeof...(Indices)>
• operator[]
  • takes a std::integral_constant<index_t, N> and returns the Nth value in Indices...

template function cxl::make_index_range<index_t First, index_t Last>() returns:

• First < Last?
  • a cxl::index_range<Indices...> where Indices... starts at First ascending to Last
• First > Last?
  • a cxl::index_range<Indices...> where Indices... starts at First descending to Last

template function cxl::pow<auto N, auto E>() is a compile time power/exponent function:

• N is the base
• E is the exponent

Aggregate

include/cxl/aggregate.hpp contains the aggregate sublibrary. this sublibrary allows converting arbitrary aggregate class type objects into tuples of their member variables, or converting a sequence of variables into a struct. to convert a struct to tuple pass it into cxl::destructure(...), if it is an lvalue the tuple contains references to the members, otherwise it contains copied values. to make a struct out of a sequence of variables pass them into cxl::make_struct(...).

Integral

include/cxl/integral.hpp contains templated user-defined literal operators that allow you to easily convert literals to std::integral_constant<...>s.

• literal operator _i returns an index_t integral constant
• literal operator _i8 returns an int8_t integral constant
• literal operator _i16 returns an int16_t integral constant
• literal operator _i32 returns an int32_t integral constant
• literal operator _i64 returns an int64_t integral constant
• literal operator _u8 returns an uint8_t integral constant
• literal operator _u16 returns an uint16_t integral constant
• literal operator _u32 returns an uint32_t integral constant
• literal operator _u64 returns an uint64_t integral constant

Iterator

include/cxl/iterator.hpp contains an adaptable constexpr iterator class cxl::iterator<...> which can support any constexpr class that implements the following methods properly:

• constexpr auto begin() const
• constexpr auto end() const
• template<typename T, T value>
constexpr auto operator[](std::integral_constant<T,value>) const

String

include/cxl/string.hpp contains a string class cxl::string<...> with a completely constexpr compatible interface. It also supports the cxl::iterator<...>s. Elements can be accesed through an iterator, operator[] or converting to const char*. String can be created through a macro STR("string"), because C++17 does not support templated user-defined string literals. The long way would be cxl::string<'s','t','r','i','n','g'>{}

Typelist

include/cxl/typelist.hpp contains the typelist sublibrary which has a few transform functions and different ways to apply/expand a typelist into a user template. It is compatible with the iterator sublibrary.

methods for empty typelists include:

• .append(Typelist)
  • expands a typelist into this, the only valid operation for an empty typelist

methods for non-empty typelists include:

• .subrange(Begin, End)
  • returns a range of types indicated by two inclusive compile-time indices
• .insert(Typelist)
  • expands another typelist into this typelist at given index
• .append(Typelist)
  • expands a typelist into the end of this typelist
• .prepend(Typelist)
  • expands a typelist into the beginning of this typelist
• .erase(Index)
  • returns a typelist, with type at given index removed
• .erase(Begin, End)
  • returns a typelist, with types between given indices removed
• .erase(BeginIter, EndIter)
  • returns a typelist, with types between given iterators removed
• .applied_emplacer()
  • applies types to a templated class and returns an emplacer for that class
• .template index_of<T>()
  • for a given type, returns index of first occurence
• .type_emplacer(Index)
  • returns a proxy constructor for a type at given index
• .operator[](Index)
  • equivalent to type_emplacer, enables cxl::iterator compatibility
• .front()
  • returns a proxy constructor for the first type
• .back()
  • returns a proxy constructor for the last type

Parse

include/cxl/parse*.hpp headers contain the parsing sublibrary in cxl::parse namespace. There are a handful of predefined fundamental parsers, which operate on cxl::string<...>s. These parsers can be combined in many different ways to create more complex parsers. When a parse operation is performed using the parser, it will return a cxl::parse::parsed<...> that can tell you if the parse was a success, how far the parser matched, what remains to be parsed and a generated typelist. subparsers can generate custom types, however if they do not, the generated type will be a cxl::string<...> filled with what the subparser matched. custom generated types are just a templated class taking a parameter pack. see example csv parser-generator in example/csv

For example, here is a default generating parser:

using namespace cxl::parse;
constexpr auto parser = one_string(STR("abc"));
constexpr auto result = parser.parse(STR("abc"));

in this case result.tree() would return a typelist<string<'a','b','c'>>

But if we have a custom generated type:

template<typename... T>
struct synth{};

using namespace cxl::parse;
constexpr auto parser = one_string(STR("abc")).generate(synth<>{});
constexpr auto result = parser.parse(STR("abc"));

now result.tree() will return a typelist<synth<string<'a','b','c'>>>.

Built-in parser classes include:

• one_string
  • (constructor)(TargetString): takes a string as target
  • .parse(StringToParse): parses a string and matches target; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• one_char
  • (constructor)(TargetString): takes a string as target
  • .parse(StringToParse): parses first character in a string and matches any character in target; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• before
  • (constructor)(TargetParser): takes another parser as target
  • .parse(StringToParse): parses a string and matches target; does not consume on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• filter
  • (constructor)(TargetParser): takes another parser as target
  • .parse(StringToParse): parses a string and matches anything but target; consumes one character on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• optional
  • (constructor)(TargetParser): takes another parser as target
  • .parse(StringToParse): parses a string and always returns success; consumes if the target succeeds
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• one_or_more
  • (constructor)(TargetParser): takes another parser as target
  • .parse(StringToParse): parses a string and matches the target aleast one time; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• zero_or_more
  • (constructor)(TargetParser): takes another parser as target
  • .parse(StringToParse): parses a string and matches the target aleast zero times; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• repeat, repeat_minimum, repeat_maximum, repeat_range: four types of repeat parsers are implemented
  • (constructor)(TargetParser, Index, [OptionalIndex]): takes another parser as target, and some constraints
  • .parse(StringToParse): parses a string and matches the target the specified allowed amount of times; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• sequence
  • (constructor)(TargetParsers...): takes an ordered sequence of parsers as targets
  • .parse(StringToParse): parses a string and matches all the targets in the order they were specifed; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• one_of
  • (constructor)(TargetParsers...): takes an ordered sequence of parsers as targets
  • .parse(StringToParse): parses a string and only matches one of the targets, trying in the order they were specifed; consumes on success
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success
• anything
  • .parse(StringToParse): parses a string and always matches one single character; always consumes
  • .generate(GeneratorTemplate): returns a new parser matching this one in behaviour, but producing user defined types into the parse tree on success

Parser Generator

• generator
  • (constructor)(TargetParsers): takes a parser as target and an output template to generate
  • .parse(StringToParse): parses a string using the targets output to generate an synthesized type; consumes if target consumes