The Scan structure

The Scan structure provides C-style conversions from string representations.

Synopsis

signature SCAN
structure Scan : SCAN

Interface

datatype fmt_item
  = ATOM of Atom.atom
  | LINT of LargeInt.int
  | INT of Int.int
  | LWORD of LargeWord.word
  | WORD of Word.word
  | WORD8 of Word8.word
  | BOOL of bool
  | CHR of char
  | STR of string
  | REAL of Real.real
  | LREAL of LargeReal.real
  | LEFT of (int * fmt_item)
  | RIGHT of (int * fmt_item)

exception BadFormat

val sscanf : string -> string -> fmt_item list option
val scanf  : string -> (char, 'a) StringCvt.reader
      -> (fmt_item list, 'a) StringCvt.reader

Description

datatype fmt_item

This datatype, which is the same type as Format.fmt_item, is used as a union type to represent the results of scanning input.

LINT n

wraps a large integer value n to convert (the conversion specifier must be one of “d”, “o”, “x”, or “X”).

INT n

wraps a default integer value n to convert (the conversion specifier must be one of “d”, “o”, “x”, or “X”).

BOOL b

wraps a Boolean value b to convert (the conversion specifier must be “b”).

CHR c

wraps a character value (the conversion specifier must be “c”).

STR s

wraps a string value s to convert (the conversion specifier must be “s”). The conversion is the identity; e.g., STR "\n" will produce a newline in the result string.

REAL r

wraps a default real value r to convert (the conversion specifier must be one of “e”, “E”, “f”, “F”, “g”, or “G”).

ATOM atm

this constructor will never be returned by scanf or sscanf.

LWORD w

this constructor will never be returned by scanf or sscanf.

WORD w

this constructor will never be returned by scanf or sscanf.

WORD8 w

this constructor will never be returned by scanf or sscanf.

LREAL r

this constructor will never be returned by scanf or sscanf.

LEFT _

this constructor will never be returned by scanf or sscanf.

RIGHT _

this constructor will never be returned by scanf or sscanf.

exception BadFormat

This exception is raised when either sscanf or scanf is applied to an ill-formed format string.

val sscanf : string → string → fmt_item list option

sscanf fmt s scans the string s using the format specifier fmt. If successful, SOME items is returned, where each item in the items list corresponds to a specified item in fmt. If the input cannot be scanned according to fmt, then NONE is returned. If the format string is ill formed, then the BadFormat exception will be raised when sscanf fmt is evaluated.

val scanf : string → (char, 'a) StringCvt.reader → (fmt_item list, 'a) StringCvt.reader

sscanf fmt getc returns a reader that scan a character stream using the format specifier fmt. If the format string is ill formed, then the BadFormat exception will be raised when scanf fmt is evaluated.

Format Strings

The sscanf and `scanf functions take a format string as their first argument. The format string is composed of zero or more directives, which are either ordinary characters (excluding %) or conversion specifiers. The result of applying one of the scan functions to an input will be a list of fmt_item corresponding to the conversion specifiers in the format string. All conversions are introduced by the % character. The format string may also contain other characters. White space (such as blanks, tabs, or newlines) in the format string match any amount of white space, including none, in the input. Everything else matches only itself. Scanning stops when an input character does not match such a format character. Scanning also stops when an input conversion cannot be made (see below).

To be written

See Also

Format, The Util Library