Strings¶
The following documentation consists of functions and methods used to
manipulate and process Chapel strings. See the IO
documentation for
more information on reading, writing, and formatting strings.
Warning
While string
is intended to be a Unicode string, there is much
left to do. As of Chapel 1.13, only ASCII strings can be expected to work
correctly with all functions.
Future work involves support for both ASCII and unicode strings, and allowing users to specify the encoding for individual strings.
-
record
string
¶ -
proc
string
(s: string, owned: bool = true)¶ Construct a new string from
s
. Ifowned
is set totrue
thens
will be fully copied into the new instance. If it isfalse
a shallow copy will be made such that any in-place modifications to the new string may appear ins
. It is the responsibility of the user to ensure that the underlying buffer is not freed while being used as part of a shallow copy.
-
proc
string
(cs: c_string, owned: bool = true, needToCopy: bool = true) Construct a new string from the c_string cs. If owned is set to true, the backing buffer will be freed when the new record is destroyed. If needToCopy is set to true, the c_string will be copied into the record, otherwise it will be used directly. It is the responsibility of the user to ensure that the underlying buffer is not freed if the c_string is not copied in.
-
proc
string
(buff: bufferType, length: int, size: int, owned: bool = true, needToCopy: bool = true) Construct a new string from buff ( c_ptr(uint(8)) ). size indicates the total size of the buffer available, while len indicates the current length of the string in the buffer (the common case would be size-1 for a C-style string). If owned is set to true, the backing buffer will be freed when the new record is destroyed. If needToCopy is set to true, the c_string will be copied into the record, otherwise it will be used directly. It is the responsibility of the user to ensure that the underlying buffer is not freed if the c_string is not copied in.
-
proc
length
¶ Returns: The number of characters in the string.
-
proc
localize
(): string¶ Gets a version of the
string
that is on the currently executing locale.Returns: A shallow copy if the string
is already on the current locale, otherwise a deep copy is performed.
-
proc
c_str
(): c_string¶ Get a c_string from a
string
.Warning
This can only be called safely on a
string
whose home is the current locale. This property can be enforced by callingstring.localize()
beforec_str()
. If the string is remote, the program will halt.For example:
var my_string = "Hello!"; on different_locale { printf("%s", my_string.localize().c_str()); }
Returns: A c_string that points to the underlying buffer used by this string
. The returned c_string is only valid when used on the same locale as the string.
-
iter
these
(): string¶ Iterates over the string character by character.
For example:
var str = "abcd"; for c in str { writeln(c); }
Output:
a b c d
-
proc
string
(i: int): string Index into a string
Returns: A string with the character at the specified index from 1..string.length
-
proc
string
(r: range(?)): string Slice a string. Halts if r is not completely inside the range 1..string.length.
Arguments: r -- range of the indices the new string should be made from Returns: a new string that is a substring within 1..string.length. If the length of r is zero, an empty string is returned.
-
proc
isEmptyString
(): bool¶ Returns: - true -- when the string is empty
- false -- otherwise
-
proc
startsWith
(needles: string ...): bool¶ Arguments: needles -- A varargs list of strings to match against. Returns: - true -- when the string begins with one or more of the needles
- false -- otherwise
-
proc
endsWith
(needles: string ...): bool¶ Arguments: needles -- A varargs list of strings to match against. Returns: - true -- when the string ends with one or more of the needles
- false -- otherwise
-
proc
find
(needle: string, region: range(?) = 1..): int¶ Arguments: - needle -- the string to search for
- region -- an optional range defining the substring to search within, default is the whole string. Halts if the range is not within 1..string.length
Returns: the index of the first occurrence of needle within a string, or 0 if the needle is not in the string.
-
proc
rfind
(needle: string, region: range(?) = 1..): int¶ Arguments: - needle -- the string to search for
- region -- an optional range defining the substring to search within, default is the whole string. Halts if the range is not within 1..string.length
Returns: the index of the first occurrence from the right of needle within a string, or 0 if the needle is not in the string.
-
proc
count
(needle: string, region: range(?) = 1..): int¶ Arguments: - needle -- the string to search for
- region -- an optional range defining the substring to search within, default is the whole string. Halts if the range is not within 1..string.length
Returns: the number of times needle occurs in the string
-
proc
replace
(needle: string, replacement: string, count: int = -1): string¶ Arguments: - needle -- the string to search for
- replacement -- the string to replace needle with
- count -- an optional integer specifying the number of replacements to make, values less than zero will replace all occurrences
Returns: a copy of the string where needle replaces replacement up to count times
-
iter
split
(sep: string, maxsplit: int = -1, ignoreEmpty: bool = false)¶ Splits the string on sep yielding the substring between each occurrence, up to maxsplit times.
Arguments: - sep -- The delimiter used to break the string into chunks.
- maxsplit -- The number of times to split the string, negative values indicate no limit.
- ignoreEmpty --
- When true -- Empty strings will not be yielded,
- and will not count towards maxsplit
- When false -- Empty strings will be yielded when
- sep occurs multiple times in a row.
-
iter
split
(maxsplit: int = -1, ignoreEmpty: bool = false) Works as above, but uses runs of whitespace as the delimiter.
Warning
While this function is supposed to split on groups of whitespace, it currently only splits on spaces.
-
proc
join
(S: [] string): string¶ Returns a new string of all of the strings in S with the receiving string concatenated between them.
var x = "|".join(["a","10","d"]); writeln(x); // prints: "a|10|d"
-
proc
strip
(chars: string = " trn", leading = true, trailing = true): string¶ Arguments: - chars -- A string containing each character to remove. Defaults to " trn".
- leading -- Indicates if leading occurrences should be removed. Defaults to true.
- trailing -- Indicates if trailing occurrences should be removed. Defaults to true.
Returns: A new string with all occurrences of characters in chars removed, including leading and trailing occurrences as appropriate.
-
proc
partition
(sep: string): 3*(string)¶ Splits the string on sep into a 3*string consisting of the section before sep, sep, and the section after sep. If sep is not found, the tuple will contain the whole string, and then two empty strings.
-
proc
isUpper
(): bool¶ Checks if all the characters in the string are either uppercase (A-Z) or uncased (not a letter).
returns: - true -- when there are no lowercase characters in the string.
- false -- otherwise
-
proc
isLower
(): bool¶ Checks if all the characters in the string are either lowercase (a-z) or uncased (not a letter).
returns: - true -- when there are no uppercase characters in the string.
- false -- otherwise
-
proc
isSpace
(): bool¶ Checks if all the characters in the string are whitespace (' ', 't', 'n', 'v', 'f', 'r').
returns: - true -- when all the characters are whitespace.
- false -- otherwise
-
proc
isAlpha
(): bool¶ Checks if all the characters in the string are alphabetic (a-zA-Z).
returns: - true -- when the characters are alphabetic.
- false -- otherwise
-
proc
isDigit
(): bool¶ Checks if all the characters in the string are digits (0-9).
returns: - true -- when the characters are ditits.
- false -- otherwise
-
proc
isAlnum
(): bool¶ Checks if all the characters in the string are alphanumeric (a-zA-Z0-9).
returns: - true -- when the characters are alphanumeric.
- false -- otherwise
-
proc
isPrintable
(): bool¶ Checks if all the characters in the string are printable. Characters are defined as being printable if they are not within the range of 0x00-0x1f or are 0x7f.
returns: - true -- when the characters are alphanumeric.
- false -- otherwise
-
proc
isTitle
(): bool¶ Checks if all uppercase characters are preceded by uncased characters, and if all lowercase characters are preceded by cased characters.
Returns: - true -- when the condition described above is met.
- false -- otherwise
-
proc
toLower
(): string¶ Returns: A new string with all uppercase characters replaced with their lowercase counterpart.
-
proc
toUpper
(): string¶ Returns: A new string with all lowercase characters replaced with their uppercase counterpart.
-
proc
toTitle
(): string¶ Returns: A new string with all cased characters following an uncased character converted to uppercase, and all cased characters following another cased character converted to lowercase.
-
proc
-
proc =(ref lhs: string, rhs: string)
Copies the string rhs into the string lhs.
-
proc =(ref lhs: string, rhs_c: c_string)
Copies the c_string rhs_c into the string lhs.
Halts if lhs is a remote string.
-
proc
+
(s0: string, s1: string)¶ Returns: A new string which is the result of concatenating s0 and s1
-
proc
*
(s: string, n: integral)¶ Returns: A new string which is the result of repeating s n times. If n is less than or equal to 0, an empty string is returned. For example:
writeln("Hello! " * 3);
Results in:
Hello! Hello! Hello!
-
proc
+
(s: string, x: numeric) The following concatenation functions return a new string which is the result of casting the non-string argument to a string, and concatenating that result with s.
-
proc
+
(x: numeric, s: string)
-
proc
+
(s: string, x: enumerated)
-
proc
+
(x: enumerated, s: string)
-
proc
+
(s: string, x: bool)
-
proc
+
(x: bool, s: string)
-
proc +=(ref lhs: string, const ref rhs: string): void
Appends the string rhs to the string lhs.
-
proc
ascii
(a: string): int(32)¶ Returns: The byte value of the first character in a as an integer.