IO

The IO class provides the following methods for performing simple input and output operations:

out_string(x : String) : SELF_TYPE
out_int(x : Int) : SELF_TYPE
in_string() : String
in_int() : Int

The methods out_string and out_int print their argument, flush the standard output, and return their self parameter.

The interpreter changes every \t to a tab and every \n to a newline in the argument x to out_string before emitting the resulting string.

The method in_string reads a string from the standard input, up to but not including a newline character or the end of file. The newline character is consumed but is not made part of the returned string. If an error occurs then in_string returns "", the string of length 0. Note that while literal lexical string constants are limited to size 1024, strings generated by in_string (or String.concat, etc.) can be of arbitrary size. There is no special processing of the two-character sequences \t or \n (or, indeed \anything) during in_string. Errors include:

• no input found before end of file
• string read in contains NUL, the character with ASCII value 0 (in which case the entire string is rejected, even if there are valid characters around the NUL)

The method in_int reads a single possibly-signed integer, which may be preceded by whitespace. Any characters following the integer, up to and including the next newline, are discarded by in_int. If an error occurs then in_int returns 0. Errors include:

• no input found before end of file
• malformed input (i.e., first thing after whitespace is not a possibly-signed integer)
• integer read in is < -2147483648
• integer read in is > +2147483647

A class can make use of the methods in the IO class by inheriting from IO. It is an error to redefine the IO class.