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Read

  • Read[ stream ] reads one expression from an input stream, and returns the expression.
  • Read[ stream , type ] reads one object of the specified type.
  • Read[ stream , , , ... ] reads a sequence of objects of the specified types.
  • Possible types to read are:
  • Objects of type Real can be given in the scientific notation format used by languages such as C and Fortran, as well as in standard Mathematica format. A form like 2.e5 or 2E5 as well as 2*^5 can be used to represent the number . Objects read as type Real are always returned as approximate numbers. Objects read as type Number are returned as integers if they contain no explicit decimal points.
  • The following options can be given:
  • Objects of type String must be terminated by newlines ("\n" characters).
  • You can specify any nested list of types for Read to look for. Each successive object read will be placed in the next position in the list structure. A depth-first traversal of the list structure is used.
  • Example: Read[ stream , Number, Number ] reads a pair of numbers from an input stream, and gives the result as a two-element list.
  • Read[ stream , Number, Number , Number, Number ] reads a matrix, going through each column, then each row.
  • You can use Read to get objects to insert into any expression structure, not necessarily a list. Example: Read[ stream , Hold[Expression]] gets an expression and places it inside Hold.
  • The first argument to Read can be InputStream[" name ", n ], or simply " name " if there is only one open input stream with the specified name.
  • You can open a file or pipe to get an InputStream object using OpenRead.
  • There is always a "current point" maintained for any stream. When you read an object from a stream, the current point is left after the input you read. Successive calls to Read can therefore be used to read successive objects in a stream such as a file.
  • Read returns EndOfFile for each object you try to read after you have reached the end of a file.
  • Read returns $Failed if it cannot read an object of the type you requested.
  • If there is a syntax error in a Mathematica expression that you try to read, then Read leaves the current point at the position of the error, and returns $Failed.
  • See the Mathematica book: Section 2.11.7.
  • See also: Input, Get, Skip, Find, StringToStream, LinkRead.
  • Related package: Utilities`BinaryFiles`.