Documentation
¶
Overview ¶
Package sexpr parses s-expressions in a manner similar to the Common Lisp reader. It supports typical s-expression syntax and customization.
The elements of S-Expressions are called "forms" by this package and represented with the Form interface in the "form" subpackage. Form provides a Value() method for obtaining the underlying value. There are specific interfaces like `String`, `Number`, `Comment`, and `SymbolForm` corresponding to typical s-expression types. Type switches and assertions may be used to cast a Form to a suitable type.
Example ¶
Example shows how ReadForm() parses a list s-expression.
r := NewFileReader("hello-world.sexpr", `("hello-world" 123)`)
f, err := r.ReadForm()
if err != nil {
fmt.Printf("got error: %s", err.Error())
}
switch ff := f.(type) {
case StringForm:
fmt.Printf("got string: %q", ff.StringValue())
case ListForm:
fmt.Printf("got list of %d elements\n", ff.Len())
}
fmt.Printf("first element: %q", f.(ListForm).Nth(0).(StringForm).StringValue())
Output: got list of 2 elements first element: "hello-world"
Index ¶
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type CommentForm ¶
type FormFactory ¶
type FormFactory interface {
// NewList returns a new form.List for the provided subforms.
//
// The passed forms slice contains whitespace and comment forms that should
// not be part of the value used to implement the form.List interface.
NewList(forms []form.Form, span SourceSpan) (form.List, error)
// NewNumberForm returns a new NumberForm for the provided literal
// representation.
//
// value is guaranteed to be one of the numeric values defined in the
// constant package.
NewNumberForm(value constant.Value, span SourceSpan) (form.Number, error)
// NewSymbolForm returns a new Form for the provided symbol literal representation.
NewSymbolForm(literal string, span SourceSpan) (form.Symbol, error)
// NewStringForm returns a new StringForm for the provided literal representation.
NewStringForm(value string, span SourceSpan) (StringForm, error)
// NewCommentForm returns a new CommentForm for the provided literal representation.
NewCommentForm(value string, span SourceSpan) (CommentForm, error)
// NewWhitespaceForm returns a new WhitespaceForm for the provided literal representation.
NewWhitespaceForm(value string, span SourceSpan) (WhitespaceForm, error)
}
FormFactory is used by FormReader to construct Form values as it processes the input stream. This allows customization of the concrete types used to implement the Form interface.
A default FormFactory is provided by DefaultFormFactory().
func DefaultFormFactory ¶
func DefaultFormFactory(r *FormReader) FormFactory
DefaultFormFactory returns a FormConstructor that creates Form objects using unexported types within the sexpr package.
type FormReader ¶
type FormReader struct {
// contains filtered or unexported fields
}
FormReader reads a stream of S-Expressions.
func NewFileReader ¶
func NewFileReader(fileName, contents string, opts ...Option) *FormReader
NewFileReader returns an object for reading Forms from a source file, which is provided as a string.
The filename value is used to print error messages and will not be accessed by the reader, so it does not need to be a real file at all.
func (*FormReader) ReadForm ¶
func (fr *FormReader) ReadForm() (Form, error)
ReadForm reads the next form in the input stream.
If the end of the file is encountered, the second value will be io.EOF.
type Option ¶
type Option interface {
// contains filtered or unexported methods
}
Option is used to configure a FormReader.
func CustomFormFactory ¶
func CustomFormFactory(factoryProvider func(*FormReader) FormFactory) Option
CustomFormFactory returns an Option that may be passed to NewFileReader that uses a non-default FormFactory for constructing Forms.
The passed in function will be called with a newly created *FormReader as an argument, allowing the factory to depend on the reader to implement its functionality.
type ReaderMacroResult ¶
type ReaderMacroResult interface {
// Skip returns true if the reader macro declined to read from the stream
// and returned the cursor back to the original location. If true is
// rturned, the Form() function will not be called.
Skip() bool
// The form read by the reader macro.
Form() form.Form
}
ReaderMacroResult is returned by custom reader macro functions.
type SourceSpan ¶
type SourceSpan = form.SourcePosition
type StringForm ¶
type ValuelessForm ¶
type WhitespaceForm ¶
type WhitespaceForm = form.Whitespace
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