isnull

Name

isnull -- test re for equivalence to empty string

Synopsis

isnull re

isnull <re

Description

isnull tests re to see if it is the empty string. isnull returns 1 and writes is empty string on standard Output if re is the empty string; it returns 0 and writes is not empty string otherwise.

re must conform to the Grail format for regular expressions.

Examples

% cat re1
{}

% isnull re1
is not empty string

% cat re2
""
% isnull re2
is empty string

% cat re3
(a+b)*(abc)

% isnull re3
is not empty string

Authors