StringFreeQ¶

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description¶

StringFreeQ["string", patt]

Gives True if no substring of "string" matches the string expression patt, and False otherwise.

StringFreeQ["string", {p1, p2, ...}]

Gives True if no substring matches any of the pi.

StringFreeQ[{s1, s2, ...}, patt]

Gives the list of results for each of the si.

StringFreeQ[patt]

Represents an operator form that can be applied to a string. Equivalent to !StringContainsQ["string", patt]. Options: IgnoreCase -> True treats upper/lowercase as equivalent.

Examples (7)¶

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (3)¶

In[1]:= StringFreeQ["abcd", "a"]
Out[1]= False

In[2]:= StringFreeQ["abcade", x_ ~~ x_]
Out[2]= True

In[3]:= StringFreeQ[{"ability", "listable", "argument"}, "a" ~~ __ ~~ "t" ~~ ___]
Out[3]= {False, True, False}

Options (1)¶

In[4]:= StringFreeQ["ac", IgnoreCase -> True]["BACCD"]
Out[4]= False

Applications (3)¶

Nothing matches, so free

In[5]:= StringFreeQ["abcdef", "xyz"]
Out[5]= True

A substring matches, so not free

In[6]:= StringFreeQ["abcdef", "cd"]
Out[6]= False

Letters are present

In[7]:= StringFreeQ["hello", LetterCharacter]
Out[7]= False

Implementation notes¶

Algorithm. StringFreeQ is the SQ_FREE face of the shared sq_dispatch core (src/strings/regex/stringcontainsq.c). The matching is identical to StringContainsQ — one regex_match per rule with an early exit — but sq_answer inverts the result, so StringFreeQ is True exactly when no rule matches anywhere. Option seeding, the curried operator form, and list-threading are all shared.

Data structures. As StringContainsQ: a RegexRule array, whole-match pair only, no capture pool.

Complexity / limits. StringFreeQ[s, p] == !StringContainsQ[s, p] by construction. An IgnoreCase option is honoured; a list of patterns means "free of any of them" (an empty list matches nothing). A non-string subject leaves the call unevaluated; byte semantics.

Attributes: Protected.

References¶

See also: StringContainsQ

Source: src/strings/regex/stringcontainsq.c
Specification: docs/spec/builtins/string-operations.md
Tests: tests/test_dsolve.c
Tests: tests/test_string_review.c
Tests: tests/test_stringcontainsq.c
Tests: tests/test_stringfns.c

Notes & additional examples¶

Notes¶

StringFreeQ is the exact negation of StringContainsQ and shares its implementation (one SqKind tag selects the inverting answer). It is True when no substring matches the pattern.

It takes an IgnoreCase option and offers the curried operator form StringFreeQ[patt]. A list of patterns means "free of any of them".