Empty string: Difference between revisions
Rename Perl 6 -> Raku, alphabetize, minor clean-up
Thundergnat (talk | contribs) (Rename Perl 6 -> Raku, alphabetize, minor clean-up) |
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/* or compare to a known empty string, same thing. "== 0" means strings are equal */
if (strcmp(str, "") == 0) { ... }
</lang>
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}</lang>
=={{header|
<lang cpp>#include <string>
// ...
// empty string declaration
std::string str; // (default constructed)
std::string str(); // (default constructor, no parameters)
std::string str{}; // (default initialized)
std::string str(""); // (const char[] conversion)
std::string str{""}; // (const char[] initializer list)
if (str.empty()) { ... } // to test if string is empty
// we could also use the following
if (str.length() == 0) { ... }
if (str == "") { ... }
// make a std::string empty
str.clear(); // (builtin clear function)
str = ""; // replace contents with empty string
str = {}; // swap contents with temp string (empty),then destruct temp
// swap with empty string
std::string tmp{}; // temp empty string
str.swap(tmp); // (builtin swap function)
std::swap(str, tmp); // swap contents with tmp
// create an array of empty strings
std::string s_array[100]; // 100 initialized to "" (fixed size)
std::array<std::string, 100> arr; // 100 initialized to "" (fixed size)
std::vector<std::string>(100,""); // 100 initialized to "" (variable size, 100 starting size)
// create empty string as default parameter
void func( std::string& s = {} ); // {} generated default std:string instance
</lang>
=={{header|Caché ObjectScript}}==
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}
}</lang>
=={{header|Delphi}}==
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if s <> '' then
PrintLn('not empty');</lang>
=={{header|Dyalect}}==
Demonstrate how to assign an empty string to a variable:
<lang dyalect>var str = ""</lang>
Demonstrate how to check that a string is empty:
<lang dyalect>if !str { }
//or
if str.isEmpty() { }</lang>
Demonstrate how to check that a string is not empty:
<lang dyalect>if str { }
//or
if !str.isEmpty() { }</lang>
=={{header|Déjà Vu}}==
Like in Python, empty strings are falsy, non-empty strings are truthy.
<lang dejavu>local :e ""
if not e:
!print "an empty string"
if e:
!print "not an empty string"</lang>
=={{header|EasyLang}}==
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-- string is not empty
end if</lang>
=={{header|F_Sharp|F#}}==
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With F90, compound data aggregates can be defined and as well procedures for operating on them, so that, after a great deal of syntactic struggle, a string data type will be available. F2000 standardised one such scheme whereby character variables are de-allocated and re-allocated with usage so that a statement such as <code>TEXT = "This" // "That"</code> would cause a de-allocation of whatever storage had been associated with TEXT followed by a re-allocation of storage for eight characters, the required size, and LEN(TEXT) would give 8.
=={{header|Free Pascal}}==
Assigning an empty string:
<lang pascal>s := '';</lang>
Checking for an empty string:
<lang pascal>s = ''
length(s) = 0</lang>
Checking for a non-empty string:
<lang pascal>s <> ''
length(s) > 0
longBool(length(s))</lang>
The <code>sysUtils</code> unit defines the constants <code>emptyStr</code> and <code>emptyWideStr</code>, which can be used in place of <code>''</code>.
=={{header|FreeBASIC}}==
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String is not empty
</pre>
=={{header|FutureBasic}}==
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System.out.println("s is not empty");
}</lang>
=={{header|JavaScript}}==
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<lang Oforth>"" isEmpty
"" isEmpty not</lang>
=={{header|Ol}}==
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Variable w does not contain the empty string
this is not a good test</pre>
=={{header|OpenEdge/Progress}}==
Strings can be stored in CHARACTER and LONGCHAR variables. Both are initially empty. Both can also be unknown. A CHARACTER has a maximum length of approx 32000 bytes.
<lang progress>DEFINE VARIABLE cc AS CHARACTER.
IF cc > '' THEN
MESSAGE 'not empty' VIEW-AS ALERT-BOX.
ELSE IF cc = ? THEN
MESSAGE 'unknown' VIEW-AS ALERT-BOX.
ELSE /* IF cc = '' */
MESSAGE 'empty' VIEW-AS ALERT-BOX.
</lang>
=={{header|PARI/GP}}==
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$s = "0 but true";
if ($s) { ... } # it's true! black magic!</lang>
=={{header|Phix}}==
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if length(s) > 0 then ... /* to test for a non-empty string */
</lang>
=={{header|PowerShell}}==
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(define (string-null? s) (string=? "" s))
(define (string-not-null? s) (string<? "" s))</lang>
=={{header|Raku}}==
(formerly Perl 6)
<lang perl6>my $s = '';
say 'String is empty' unless $s;
say 'String is not empty' if $s;</lang>
Unlike in Perl 5, only empty strings test as false - the string "0" tests as true now.
=={{header|Rascal}}==
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