Classes - stdout and stderr

The stdout and stderr classes provide I/O stream implementations that write to the process's standard output and standard error streams. The two classes implement the iostream API, and can be used as follows:

:- import(stdout).
:- import(stderr).

main(Args)
{
    new stdout(Stdout);
    Stdout.writeln("Hello World!");

    new stderr(Stderr);
    Stderr.writeln("Hello Error!");

    Stdout.writeln("Arguments: " + Args);
}

The stdout and stderr classes also provide some static convenience methods which remove the need to create an object first:

:- import(stdout).
:- import(stderr).

main(Args)
{
    stdout::writeln("Hello World!");
    stderr::writeln("Hello Error!");
    stdout::writeln("Arguments: " + Args);
}

Parent class: iostream

Class members: override canWrite()
override flush()
override writeByte(Byte)
override writeString(String)
static flush()
static write(Term)
static writeln(Term)
static writeln()
static writeTerm(Term)
static writeTerm(Term, Vars)

See Also: stdin

stdout::flush()
stderr::flush()

Description: Flushes all data that has been written so far to standard output (or standard error).

Examples

stdout::write("| ?- ");
stdout::flush();
Stdin.readTerm(Term);

See Also: write(), iostream::flush()

stdout::write(Term)
stderr::write(Term)

Description: If Term is a string, then write it directly to standard output (or standard error) without quoting.

: If Term has the form (A + B), then write A and B to the output without the plus sign. This rule is applied recursively for writing terms such as (A + B + C + ...).

: If Term is not a string or of the form (A + B), then write it using the same representation and quoting rules as writeTerm().

Examples

Answer is 2 + 2;
stdout::write("The answer is: " + Answer);
stdout::writeln();

The answer is: 4

See Also: flush(), writeln(), writeTerm(), iostream::write()

stdout::writeln(Term)
stdout::writeln()
stderr::writeln(Term)
stderr::writeln()

Description: If Term is a string, then write it directly to standard output (or standard error) without quoting.

: If Term has the form (A + B), then write A and B to the output without the plus sign. This rule is applied recursively for writing terms such as (A + B + C + ...).

: If Term is not a string or of the form (A + B), then write it using the same representation and quoting rules as writeTerm().

: A newline is written after Term. If Term is omitted, then only a newline is written.

Examples

Answer is 2 + 2;
stdout::writeln("The answer is: " + Answer);

The answer is: 4

See Also: write(), writeTerm(), iostream::writeln()

stdout::writeTerm(Term)
stdout::writeTerm(Term, Vars)
stderr::writeTerm(Term)
stderr::writeTerm(Term, Vars)

Description: Write Term to standard output (or standard error) in a form that is compatible with the Plang source parser for terms. The Term is not terminated with a "." or end of line marker.

: If Vars is present, then it must be a list of Name = Var declarations. If Var is encountered as an unbound variable in Term, then it will be written to Stream as Name. Variables not listed in Vars will be written as "_N", where "N" is the variable's pointer value. If Vars is not present, then all unbound variables are written as "_N". Name must be an atom or string.

Errors

instantiation_error - Vars is a variable.
type_error(variable_names, Vars) - Vars is not a valid list of variable names.

Examples

stdout::writeTerm(A - B * 1.5 + pi / 2);
    produces: _1f95460 - _1f95420 * 1.5 + pi / 2

stdout::writeTerm(A - B * 1.5 + pi / 2, ["A" = A, "B" = B]);
    produces: A - B * 1.5 + pi / 2

See Also: write(), writeln(), iostream::writeTerm()