SYS-PRINT(2) SYS-PRINT(2)
NAME
print, fprint, sprint - print formatted output
SYNOPSIS
include "sys.m";
sys := load Sys Sys->PATH;
fprint: fn(fd: ref FD, format: string, *): int;
print: fn(format: string, *): int;
sprint: fn(format: string, *): string;
DESCRIPTION
These functions format and print their arguments as UTF
text. Print writes text to the standard output. Fprint
writes to the named output file descriptor. Sprint places
text in a string, which it returns. Print and fprint return
the number of bytes transmitted or a negative value if an
error was encountered when writing the output.
Each of these functions converts, formats, and prints its
trailing arguments under control of a format string. The
format contains two types of objects: plain characters,
which are simply copied to the output stream, and conversion
specifications, each of which results in fetching of zero or
more arguments. The Limbo compiler recognizes calls to
these functions and checks that the arguments match the for-
mat specifications in number and type.
Each conversion specification has the following format:
% [flags] verb
The verb is a single character and each flag is a single
character or a (decimal) numeric string. Up to two numeric
strings may be used; the first is called f1, the second f2.
They can be separated by `.', and if one is present, then f1
and f2 are taken to be zero if missing, otherwise they are
considered `omitted'. Either or both of the numbers may be
replaced with the character *, meaning that the actual num-
ber will be obtained from the argument list as an integer.
The flags and numbers are arguments to the verb described
below.
d, o, x,
The numeric verbs d, o, and x format their int argu-
ments in decimal, octal, and hexadecimal (with hex dig-
its in lower-case). The flag b is required when the
corresponding value is a Limbo big, not an int. Argu-
ments are taken to be signed, unless the u flag is
given, to force them to be treated as unsigned. Each
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SYS-PRINT(2) SYS-PRINT(2)
interprets the flags # and - to mean alternative format
and left justified. If f2 is not omitted, the number
is padded on the left with zeros until at least f2 dig-
its appear. Then, if alternative format is specified
for x conversion, the number is preceded by 0x.
Finally, if f1 is not omitted, the number is padded on
the left (or right, if left justification is specified)
with enough blanks to make the field at least f1 char-
acters long. The verb X is similar to x, except that
the hexadecimal digits are displayed in upper-case, and
in alternative format, the number is preceded by 0X.
e, f, g
The floating point verbs e, f, and g take a real argu-
ment. Each interprets the flags +, -, and # to mean
always print a sign, left justified, and alternative
format. F1 is the minimum field width and, if the con-
verted value takes up less than f1 characters, it is
padded on the left (or right, if `left justified') with
spaces. F2 is the number of digits that are converted
after the decimal place for e and f conversions, and f2
is the maximum number of significant digits for g con-
versions. The f verb produces output of the form
[-]
h.stigiddnefernamlmth.stigidtratsfernamlmt
h.2fdnefernamlmth.2ftratsfernamlmt
h&lmtlt;&4Hgt; h&lmtlt;&4H/gt;
h&lmtlt;&4Hgt; h&lmtlt;&4H/gt;
h,)2(ortni-sysdnefernamlmth,)2(ortni-systratsfernamlmth)2(nepo-sysdnefernamlmth)2(nepo-systratsfernamlmt
h&lmtlt;&4Hgt; h&lmtlt;&4H/gt;