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 Go to latest Published: Oct 13, 2020 License: GPL-3.0 Imports: 14 Imported by: 0

Documentation

Overview

Package sabre provides data structures, reader for reading LISP source into data structures and functions for evluating forms against a context.

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrSkip can be returned by reader macro to indicate a no-op form which
	// should be discarded (e.g., Comments).
	ErrSkip = errors.New("skip expr")

	// ErrEOF is returned when stream ends prematurely to indicate that more
	// data is needed to complete the current form.
	ErrEOF = errors.New("unexpected EOF")
)
View Source 
var (
	// Def implements (def symbol value) form for defining bindings.
	Def = SpecialForm{
		Name:  "def",
		Parse: parseDef,
	}

	// Lambda defines an anonymous function and returns. Must have the form
	// (fn* name? [arg*] expr*) or (fn* name? ([arg]* expr*)+)
	Lambda = SpecialForm{
		Name:  "fn*",
		Parse: fnParser(false),
	}

	// Macro defines an anonymous function and returns. Must have the form
	// (macro* name? [arg*] expr*) or (fn* name? ([arg]* expr*)+)
	Macro = SpecialForm{
		Name:  "macro*",
		Parse: fnParser(true),
	}

	// Let implements the (let [binding*] expr*) form. expr are evaluated
	// with given local bindings.
	Let = SpecialForm{
		Name:  "let",
		Parse: parseLet,
	}

	// Do special form evaluates args one by one and returns the result of
	// the last expr.
	Do = SpecialForm{
		Name:  "do",
		Parse: parseDo,
	}

	// If implements if-conditional flow using (if test then else?) form.
	If = SpecialForm{
		Name:  "if",
		Parse: parseIf,
	}

	// SimpleQuote prevents a form from being evaluated.
	SimpleQuote = SpecialForm{
		Name:  "quote",
		Parse: parseSimpleQuote,
	}

	// SyntaxQuote recursively applies the quoting to the form.
	SyntaxQuote = SpecialForm{
		Name:  "syntax-quote",
		Parse: parseSyntaxQuote,
	}

	Recur = SpecialForm{
		Name:  "recur",
		Parse: parseRecur,
	}
)
View Source 
var ErrResolving = errors.New("unable to resolve symbol")

ErrResolving is returned when a scope implementation fails to resolve a binding for given symbol.

Functions

func Compare 

func Compare(v1, v2 Value) bool

Compare compares two values in an identity independent manner. If v1 has `Compare(Value) bool` method, the comparison is delegated to it as `v1.Compare(v2)`.

Types

type Any 

type Any struct{ V reflect.Value }

Any can be used to wrap arbitrary Go value into spirit scope.

func (Any) Eval 

func (any Any) Eval(_ Scope) (Value, error)

Eval returns itself.

func (Any) String 

func (any Any) String() string

type Bool 

type Bool bool

Bool represents a boolean value.

func (Bool) Eval 

func (b Bool) Eval(_ Scope) (Value, error)

Eval returns the underlying value.

func (Bool) String 

func (b Bool) String() string

type Character 

type Character rune

Character represents a character literal. For example, \a, \b, \1, \∂ etc are valid character literals. In addition, special literals like \newline, \space etc are supported by the reader.

func (Character) Eval 

func (char Character) Eval(_ Scope) (Value, error)

Eval simply returns itself since Chracters evaluate to themselves.

func (Character) String 

func (char Character) String() string

type EvalError 

type EvalError struct {
	Position
	Cause error
	Form  Value
}

EvalError represents error during evaluation.

func (EvalError) Error 

func (ee EvalError) Error() string

func (EvalError) Unwrap 

func (ee EvalError) Unwrap() error

Unwrap returns the underlying cause of this error.

type Float64 

type Float64 float64

Float64 represents double precision floating point numbers represented using decimal or scientific number formats.

func (Float64) Eval 

func (f64 Float64) Eval(_ Scope) (Value, error)

Eval simply returns itself since Floats evaluate to themselves.

func (Float64) String 

func (f64 Float64) String() string

type Fn 

type Fn struct {
	Args     []string
	Variadic bool
	Body     Value
	Func     func(scope Scope, args []Value) (Value, error)
}

Fn represents a function or macro definition.

func (*Fn) Compare 

func (fn *Fn) Compare(v Value) bool

Compare returns true if 'other' is also a function and has the same signature and body.

func (*Fn) Eval 

func (fn *Fn) Eval(_ Scope) (Value, error)

Eval returns the function itself.

func (*Fn) Invoke 

func (fn *Fn) Invoke(scope Scope, args ...Value) (Value, error)

Invoke executes the function with given arguments.

func (Fn) String 

func (fn Fn) String() string

type HashMap 

type HashMap struct {
	Position
	Data map[Value]Value
}

HashMap represents a container for key-value pairs.

func (*HashMap) Eval 

func (hm *HashMap) Eval(scope Scope) (Value, error)

Eval evaluates all keys and values and returns a new HashMap containing the evaluated values.

func (*HashMap) Get 

func (hm *HashMap) Get(key Value, def Value) Value

Get returns the value associated with the given key if found. Returns def otherwise.

func (*HashMap) Keys 

func (hm *HashMap) Keys() Values

Keys returns all the keys in the hashmap.

func (*HashMap) Set 

func (hm *HashMap) Set(key, val Value) error

Set sets/updates the value associated with the given key.

func (*HashMap) String 

func (hm *HashMap) String() string

func (*HashMap) Values 

func (hm *HashMap) Values() Values

Values returns all the values in the hashmap.

type Int64 

type Int64 int64

Int64 represents integer values represented using decimal, octal, radix and hexadecimal formats.

func (Int64) Eval 

func (i64 Int64) Eval(_ Scope) (Value, error)

Eval simply returns itself since Integers evaluate to themselves.

func (Int64) String 

func (i64 Int64) String() string

type Invokable 

type Invokable interface {
	Value
	Invoke(scope Scope, args ...Value) (Value, error)
}

Invokable represents any value that supports invocation. Vector, Fn etc support invocation.

type Keyword 

type Keyword string

Keyword represents a keyword literal.

func (Keyword) Eval 

func (kw Keyword) Eval(_ Scope) (Value, error)

Eval simply returns itself since Keywords evaluate to themselves.

func (Keyword) Invoke 

func (kw Keyword) Invoke(scope Scope, args ...Value) (Value, error)

Invoke enables keyword lookup for maps.

func (Keyword) String 

func (kw Keyword) String() string

type List 

type List struct {
	Values
	Position
	// contains filtered or unexported fields
}

List represents an list of forms/vals. Evaluating a list leads to a function invocation.

func (*List) Eval 

func (lf *List) Eval(scope Scope) (Value, error)

Eval performs an invocation.

func (List) String 

func (lf List) String() string

type MapScope 

type MapScope struct {
	// contains filtered or unexported fields
}

MapScope implements Scope using a Go native hash-map.

func New 

func New() *MapScope

New initializes a new scope with all the core bindings.

func NewScope 

func NewScope(parent Scope) *MapScope

NewScope returns an instance of MapScope with no bindings. If you need builtin special forms, pass result of New() as argument.

func (*MapScope) Bind 

func (scope *MapScope) Bind(symbol string, v Value) error

Bind adds the given value to the scope and binds the symbol to it.

func (*MapScope) BindGo 

func (scope *MapScope) BindGo(symbol string, v interface{}) error

BindGo is similar to Bind but handles conversion of Go value 'v' to 

Value type. See `ValueOf()`

func (*MapScope) Parent 

func (scope *MapScope) Parent() Scope

Parent returns the parent scope of this scope.

func (*MapScope) Resolve 

func (scope *MapScope) Resolve(symbol string) (Value, error)

Resolve finds the value bound to the given symbol and returns it if found in this scope or parent scope if any. Returns error otherwise.

type Module 

type Module []Value

Module represents a group of forms. Evaluating a module leads to evaluation of each form in order and result will be the result of last evaluation.

func (Module) Compare 

func (mod Module) Compare(v Value) bool

Compare returns true if the 'v' is also a module and all forms in the module are equivalent.

func (Module) Eval 

func (mod Module) Eval(scope Scope) (Value, error)

Eval evaluates all the vals in the module body and returns the result of the last evaluation.

func (Module) String 

func (mod Module) String() string

type MultiFn 

type MultiFn struct {
	Name    string
	IsMacro bool
	Methods []Fn
}

MultiFn represents a multi-arity function or macro definition.

func (MultiFn) Compare 

func (multiFn MultiFn) Compare(v Value) bool

Compare returns true if 'v' is also a MultiFn and all methods are equivalent.

func (MultiFn) Eval 

func (multiFn MultiFn) Eval(_ Scope) (Value, error)

Eval returns the multiFn definition itself.

func (MultiFn) Expand 

func (multiFn MultiFn) Expand(scope Scope, args []Value) (Value, error)

Expand executes the macro body and returns the result of the expansion.

func (MultiFn) Invoke 

func (multiFn MultiFn) Invoke(scope Scope, args ...Value) (Value, error)

Invoke dispatches the call to a method based on number of arguments.

func (MultiFn) String 

func (multiFn MultiFn) String() string

type Nil 

type Nil struct{}

Nil represents a nil value.

func (Nil) Eval 

func (n Nil) Eval(_ Scope) (Value, error)

Eval returns the underlying value.

func (Nil) String 

func (n Nil) String() string

type Position 

type Position struct {
	File   string
	Line   int
	Column int
}

Position represents the positional information about a value read by reader.

func (Position) GetPos 

func (pi Position) GetPos() (file string, line, col int)

GetPos returns the file, line and column values.

func (*Position) SetPos 

func (pi *Position) SetPos(file string, line, col int)

SetPos sets the position information.

func (Position) String 

func (pi Position) String() string

type ReadError 

type ReadError struct {
	Position
	Cause  error
	Messag string
}

ReadError wraps the parsing/eval errors with relevant information.

func (ReadError) Error 

func (err ReadError) Error() string

func (ReadError) Unwrap 

func (err ReadError) Unwrap() error

Unwrap returns underlying cause of the error.

type Reader 

type Reader struct {
	File string
	// contains filtered or unexported fields
}

Reader provides functions to parse characters from a stream into symbolic expressions or forms.

func NewReader 

func NewReader(rs io.Reader) *Reader

NewReader returns a lisp reader instance which can read forms from rs. Reader behavior can be customized by using SetMacro to override or remove from the default read table. File name will be inferred from the reader value and type information or can be set manually on the Reader.

func (*Reader) All 

func (rd *Reader) All() (Value, error)

All consumes characters from stream until EOF and returns a list of all the forms parsed. Any no-op forms (e.g., comment) returned will not be included in the result.

func (*Reader) IsTerminal 

func (rd *Reader) IsTerminal(r rune) bool

IsTerminal returns true if the rune should terminate a form. ReaderMacro trigger runes defined in the read table and all space characters including "," are considered terminal.

func (*Reader) NextRune 

func (rd *Reader) NextRune() (rune, error)

NextRune returns next rune from the stream and advances the stream.

func (*Reader) One 

func (rd *Reader) One() (Value, error)

One consumes characters from underlying stream until a complete form is parsed and returns the form while ignoring the no-op forms like comments. Except EOF, all errors will be wrapped with ReaderError type along with the positional information obtained using Position().

func (Reader) Position 

func (rd Reader) Position() Position

Position returns information about the stream including file name and the position of the reader.

func (*Reader) SetMacro 

func (rd *Reader) SetMacro(init rune, macro ReaderMacro, isDispatch bool)

SetMacro sets the given reader macro as the handler for init rune in the read table. Overwrites if a macro is already present. If the macro value given is nil, entry for the init rune will be removed from the read table. isDispatch decides if the macro is a dispatch macro and takes effect only after a '#' sign.

func (*Reader) SkipSpaces 

func (rd *Reader) SkipSpaces() error

SkipSpaces consumes and discards runes from stream repeatedly until a character that is not a whitespace is identified. Along with standard unicode white-space characters "," is also considered a white-space and discarded.

func (*Reader) Unread 

func (rd *Reader) Unread(runes ...rune)

Unread can be used to return runes consumed from the stream back to the stream. Un-reading more runes than read is guaranteed to work but might cause inconsistency in stream positional information.

type ReaderMacro 

type ReaderMacro func(rd *Reader, init rune) (Value, error)

ReaderMacro implementations can be plugged into the Reader to extend, override or customize behavior of the reader.

type Scope 

type Scope interface {
	Parent() Scope
	Bind(symbol string, v Value) error
	Resolve(symbol string) (Value, error)
}

Scope implementation is responsible for managing value bindings.

type Seq 

type Seq interface {
	Value
	// First should return first value of the sequence or nil if the
	// sequence is empty.
	First() Value
	// Next should return the remaining sequence when the first value
	// is excluded.
	Next() Seq
	// Cons should add the value to the beginning of the sequence and
	// return the new sequence.
	Cons(v Value) Seq
	// Conj should join the given values to the sequence and return a
	// new sequence.
	Conj(vals ...Value) Seq
}

Seq implementations represent a sequence/list of values.

type Set 

type Set struct {
	Values
	Position
}

Set represents a list of unique values. (Experimental)

func (Set) Eval 

func (set Set) Eval(scope Scope) (Value, error)

Eval evaluates each value in the set form and returns the resultant values as new set.

func (Set) String 

func (set Set) String() string

type SpecialForm 

type SpecialForm struct {
	Name  string
	Parse func(scope Scope, args []Value) (*Fn, error)
}

SpecialForm is a Value type for representing special forms that will be subjected to an intermediate Parsing stage before evaluation.

func (SpecialForm) Eval 

func (sf SpecialForm) Eval(_ Scope) (Value, error)

Eval always returns error since it is not allowed to directly evaluate a special form.

func (SpecialForm) String 

func (sf SpecialForm) String() string

type String 

type String string

String represents double-quoted string literals. String Form represents the true string value obtained from the reader. Escape sequences are not applicable at this level.

func (String) Conj 

func (se String) Conj(vals ...Value) Seq

Conj joins the given values to list of characters of the string and returns the new sequence.

func (String) Cons 

func (se String) Cons(v Value) Seq

Cons converts the string to character sequence and adds the given value to the beginning of the list.

func (String) Eval 

func (se String) Eval(_ Scope) (Value, error)

Eval simply returns itself since Strings evaluate to themselves.

func (String) First 

func (se String) First() Value

First returns the first character if string is not empty, nil otherwise.

func (String) Next 

func (se String) Next() Seq

Next slices the string by excluding first character and returns the remainder.

func (String) String 

func (se String) String() string

type Symbol 

type Symbol struct {
	Position
	Value string
}

Symbol represents a name given to a value in memory.

func (Symbol) Compare 

func (sym Symbol) Compare(v Value) bool

Compare compares this symbol to the given value. Returns true if the given value is a symbol with same data.

func (Symbol) Eval 

func (sym Symbol) Eval(scope Scope) (Value, error)

Eval returns the value bound to this symbol in current context. If the symbol is in fully qualified form (i.e., separated by '.'), eval does recursive member access.

func (Symbol) String 

func (sym Symbol) String() string

type Type 

type Type struct{ T reflect.Type }

Type represents the type value of a given value. Type also implements Value type.

func (Type) Eval 

func (t Type) Eval(_ Scope) (Value, error)

Eval returns the type value itself.

func (Type) Invoke 

func (t Type) Invoke(scope Scope, args ...Value) (Value, error)

Invoke creates zero value of the given type.

func (Type) String 

func (t Type) String() string

type Value 

type Value interface {
	// String should return the LISP representation of the value.
	String() string
	// Eval should evaluate this value against the scope and return
	// the resultant value or an evaluation error.
	Eval(scope Scope) (Value, error)
}

Value represents data/forms in spirit. This includes those emitted by Reader, values obtained as result of an evaluation etc.

func Eval 

func Eval(scope Scope, form Value) (Value, error)

Eval evaluates the given form against the scope and returns the result of evaluation.

func MacroExpand 

func MacroExpand(scope Scope, form Value) (Value, bool, error)

MacroExpand expands the macro invocation form.

func ReadEval 

func ReadEval(scope Scope, r io.Reader) (Value, error)

ReadEval consumes data from reader 'r' till EOF, parses into forms and evaluates all the forms obtained and returns the result.

func ReadEvalStr 

func ReadEvalStr(scope Scope, src string) (Value, error)

ReadEvalStr is a convenience wrapper for Eval that reads forms from string and evaluates for result.

func ValueOf 

func ValueOf(v interface{}) Value

ValueOf converts a Go value to spirit Value type. If 'v' is already a Value type, it is returned as is. Primitive Go values like string, rune, int, float, bool are converted to the right spirit Value types. Functions are converted to the wrapper 'Fn' type. Value of type 'reflect.Type' will be wrapped as 'Type' which enables initializing a value of that type when invoked. All other types will be wrapped using 'Any' type.

type Values 

type Values []Value

Values represents a list of values and implements the Seq interface.

func (Values) Compare 

func (vals Values) Compare(v Value) bool

Compare compares the values in this sequence to the other sequence. other sequence will be realized for comparison.

func (Values) Conj 

func (vals Values) Conj(args ...Value) Seq

Conj returns a new sequence where 'v' is appended to the values.

func (Values) Cons 

func (vals Values) Cons(v Value) Seq

Cons returns a new sequence where 'v' is prepended to the values.

func (Values) Eval 

func (vals Values) Eval(_ Scope) (Value, error)

Eval returns itself.

func (Values) First 

func (vals Values) First() Value

First returns the first value in the list if the list is not empty. Returns Nil{} otherwise.

func (Values) Next 

func (vals Values) Next() Seq

Next returns a new sequence containing values after the first one. If there are no values to create a next sequence, returns nil.

func (Values) Size 

func (vals Values) Size() int

Size returns the number of items in the list.

func (Values) String 

func (vals Values) String() string

func (Values) Uniq 

func (vals Values) Uniq() []Value

Uniq removes all the duplicates from the given value array. TODO: remove this naive implementation

type Vector 

type Vector struct {
	Values
	Position
}

Vector represents a list of values. Unlike List type, evaluation of vector does not lead to function invoke.

func (Vector) Eval 

func (vf Vector) Eval(scope Scope) (Value, error)

Eval evaluates each value in the vector form and returns the resultant values as new vector.

func (Vector) Invoke 

func (vf Vector) Invoke(scope Scope, args ...Value) (Value, error)

Invoke of a vector performs a index lookup. Only arity 1 is allowed and should be an integer value to be used as index.

func (Vector) String 

func (vf Vector) String() string

Source Files

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Directories

Path Synopsis
Package repl provides a REPL implementation and options to expose internal features through a read-eval-print-loop.
 Package repl provides a REPL implementation and options to expose internal features through a read-eval-print-loop.

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