package scanner

Import Path
	go/scanner (on

Dependency Relation
	imports 9 packages, and imported by 3 packages

Involved Source Files errors.go Package scanner implements a scanner for Go source text. It takes a []byte as source which can then be tokenized through repeated calls to the Scan method.
Code Examples package main import ( "fmt" "go/scanner" "go/token" ) func main() { // src is the input that we want to tokenize. src := []byte("cos(x) + 1i*sin(x) // Euler") // Initialize the scanner. var s scanner.Scanner fset := token.NewFileSet() // positions are relative to fset file := fset.AddFile("", fset.Base(), len(src)) // register input "file" s.Init(file, src, nil /* no error handler */, scanner.ScanComments) // Repeated calls to Scan yield the token sequence found in the input. for { pos, tok, lit := s.Scan() if tok == token.EOF { break } fmt.Printf("%s\t%s\t%q\n", fset.Position(pos), tok, lit) } }
Package-Level Type Names (total 5)
/* sort by: | */
In an [ErrorList], an error is represented by an *Error. The position Pos, if valid, points to the beginning of the offending token, and the error condition is described by Msg. Msg string Pos token.Position Error implements the error interface. Error : error
An ErrorHandler may be provided to [Scanner.Init]. If a syntax error is encountered and a handler was installed, the handler is called with a position and an error message. The position points to the beginning of the offending token. func (*Scanner).Init(file *token.File, src []byte, err ErrorHandler, mode Mode)
ErrorList is a list of *Errors. The zero value for an ErrorList is an empty ErrorList ready to use. Add adds an [Error] with given position and error message to an [ErrorList]. Err returns an error equivalent to this error list. If the list is empty, Err returns nil. An [ErrorList] implements the error interface. [ErrorList] implements the sort Interface. ( ErrorList) Less(i, j int) bool RemoveMultiples sorts an [ErrorList] and removes all but the first error per line. Reset resets an [ErrorList] to no errors. Sort sorts an [ErrorList]. *[Error] entries are sorted by position, other errors are sorted by error message, and before any *[Error] entry. ( ErrorList) Swap(i, j int) ErrorList : error ErrorList : sort.Interface
A mode value is a set of flags (or 0). They control scanner behavior. func (*Scanner).Init(file *token.File, src []byte, err ErrorHandler, mode Mode) const ScanComments
A Scanner holds the scanner's internal state while processing a given text. It can be allocated as part of another data structure but must be initialized via [Scanner.Init] before use. public state - ok to modify // number of errors encountered Init prepares the scanner s to tokenize the text src by setting the scanner at the beginning of src. The scanner uses the file set file for position information and it adds line information for each line. It is ok to re-use the same file when re-scanning the same file as line information which is already present is ignored. Init causes a panic if the file size does not match the src size. Calls to [Scanner.Scan] will invoke the error handler err if they encounter a syntax error and err is not nil. Also, for each error encountered, the [Scanner] field ErrorCount is incremented by one. The mode parameter determines how comments are handled. Note that Init may call err if there is an error in the first character of the file. Scan scans the next token and returns the token position, the token, and its literal string if applicable. The source end is indicated by [token.EOF]. If the returned token is a literal ([token.IDENT], [token.INT], [token.FLOAT], [token.IMAG], [token.CHAR], [token.STRING]) or [token.COMMENT], the literal string has the corresponding value. If the returned token is a keyword, the literal string is the keyword. If the returned token is [token.SEMICOLON], the corresponding literal string is ";" if the semicolon was present in the source, and "\n" if the semicolon was inserted because of a newline or at EOF. If the returned token is [token.ILLEGAL], the literal string is the offending character. In all other cases, Scan returns an empty literal string. For more tolerant parsing, Scan will return a valid token if possible even if a syntax error was encountered. Thus, even if the resulting token sequence contains no illegal tokens, a client may not assume that no error occurred. Instead it must check the scanner's ErrorCount or the number of calls of the error handler, if there was one installed. Scan adds line information to the file added to the file set with Init. Token positions are relative to that file and thus relative to the file set.
Package-Level Functions (only one)
PrintError is a utility function that prints a list of errors to w, one error per line, if the err parameter is an [ErrorList]. Otherwise it prints the err string.
Package-Level Constants (only one)
const ScanComments Mode = 1 // return comments as COMMENT tokens