This section describes functions that relates to manipulating string values in the APL.

Warning!

The String functions cannot operate on null arguments.

The following functions for String described here are:

String Concatenation

Strings are concatenated with the arithmetic '+' operator:

string str1 = string str2 + string str3 ...

strEndsWith

Returns true if str ends with substr , otherwise false.

boolean strEndsWith
 ( string  str , 
 string  substr )

Parameter	Description
`str`	String to examine
`substr`	String to look for
Returns	`true` or `false`

strEqualsIgnoreCase

Compares two strings and returns true if they are equal, and false if they are not. This comparison ignores case.

boolean strEqualsIgnoreCase
 ( string  str1 , 
 string  str2  )

Parameter	Description
`str1`	A string to compare
`str2`	Another string to compare
Returns	`true` or `false`

strIndexOf

Returns the first position where substr can be found in str . If substr is not found, -1 is returned. The position starts to count from 0 (zero), which is the first character.

int strIndexOf 
( string str , 
string substr, 
int startIndex ) //Optional

Parameter	Description
`str`	String to examine
`substr`	String to look for
`startIndex`	Index where to start the string search. If `startIndex` is not specified, the string is searched from the beginning.
Returns	The position of the first character of `substr` within `str` . If not found, `-1` is returned.

strLastIndexOf

Returns the last position where substr can be found in str . If substr is not found, -1 is returned. The position starts to count from 0 (zero), which is the first character.

int strLastIndexOf
 ( string  str , 
 string  substr, int startIndex  ) //Optional

Parameter	Description
`str`	String to examine
`substr`	String to look for
`startIndex`	Index where to start the string search. If `startIndex` is not specified, the string is searched from the beginning.
Returns	The position of the last character of `substr` within `str` . If not found, `-1` is returned.

strInsert

Inserts a string into another at a specific position, and returns the result string.

string strInsert
 ( string  str1 ,
 int  position ,
 string  str2  )

Parameter	Description
`str1`	The string that `str2` is inserted into
`str2`	The string to insert
`position`	Position where `str2` will be inserted. Position 0 (zero) indicates prior to the first character of `str1` .
Returns	The result string. Note, the `str1` and `str2` are not modified.

strLength

Returns the number of characters in a string.

int strLength( string  str  )

Parameter	Description
`str`	String to examine
Returns	The number of characters in the string

strREContains

Returns true if a string contains a substring, else false. The function is case sensitive.

boolean strREContains
 ( string  str ,
 string  regexp  )

Parameter	Description
`str`	String to examine
`regexp`	The substring to look for. Regular expressions are allowed.
Returns	`true` or `false`

Note!

Regular expressions according to Java syntax applies. For further information, see https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html

Warning!

Using nonconstant regular expressions may consume large amounts of memory and should therefore be avoided.

strREIndexOf

Returns the first position where a regular expression can be found in a string. If the regular expression is not found, -1 is returned. The position starts to count from 0 (zero), which is the first character.

int strREIndexOf
 ( string  str ,
 string  regexp  )

Parameter	Description
`str`	String to examine
`regexp`	Regular expression to be used when examining `str` , using `case sensitive` and `contains` (not `matches`).
Returns	The position of the first character of `regexp` within `str` . If not found, `-1` is returned.

Example - Using strREIndexOf

strREIndexOf( "Hello There!", "[Tt]he" ) // Returns 6

Note!

Regular expressions according to Java syntax applies. For further information, see https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html.

Warning!

Using nonconstant regular expressions may consume large amounts of memory and should therefore be avoided.

strREMatches

Returns true if the first stated string matches the content of the second string completely. The function is case sensitive.

boolean strREMatches
 ( string  str ,
 string  regexp  )

Parameter	Description
`str`	The first string
`regexp`	The second string. Regular expressions are allowed
Returns	`true` or `false`

Example - Using strREMatches

strREMatches( "abc", "ab." )

Will return true.

strREMatches( "abc", "a..c" )

Will return false.

strREMatches( "abc", "a[a-z]c" )

Will return true.

strREMatches( "abc", "a[A-Z]c" )

Will return false.

strREMatches( numberString, "[0-9]*" )

Will check that the variable numberString only contain digits. It will return true for "123" and false for "123F".

Note!

Regular expressions according to Java syntax applies. For further information, please refer to https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html.

Warning!

Using nonconstant regular expressions may consume large amounts of memory and should therefore be avoided.

strREReplaceAll

Replaces existing substrings within a string with new values.

string strREReplaceAll
 ( string  str ,
 string  old ,
 string  new  )

Parameter	Description
`str`	String to change
`old`	The substring to replace. Regular expressions are allowed.
`new`	The new substring to replace the old. If an empty string is entered, the old will be removed without inserting any new value.
Returns	The result string

Example - Using strREReplaceAll

string strREReplaceAll
 ( "flower", "low", "orm" )

This call will change the string "flower" to the string "low". If the new parameter was left empty ("orm" in this case), the resulting string would have been "fer".

Note!

Regular expressions according to Java syntax applies. For further information, please refer to https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/Pattern.html.

Warning!

Using nonconstant regular expressions may consume large amounts of memory and should therefore be avoided.

strReplaceChars

Replaces characters in a string at a given position with another string and returns the new string. If str2 is longer than str1 , then the resulting string will be expanded to fit the complete str2 .

string strReplaceChars
 ( string  str1 ,
 int  position ,
 string  str2  )

Parameter	Description
`str1`	The base string
`position`	Position where `str2` will start replacement in `str1` . Position 0 (zero) indicates prior to the first character of `str1` .
`str2`	String to use for replacement
Returns	The result string. Note, the `str1` and `str2` are not modified.

Example - Using strReplaceChars

The following example returns the string: Hi Walter

strReplaceChars("Hi Sister", 3, "Walt");

strSplit

Splits a string where a given regular expression is matched into a list of strings. The function will try to match the regular expression and split the string as many times as possible.

list<string> strSplit
 ( string  str ,
 string  regex  )

Parameter	Description
`str`	The base string
`regex`	The regular expression which is to be used to split elements
Returns	A list of strings

This function would typically be used for splitting strings of values that are comma separated, colon separated, or similar. The list returned will present the substrings in the order they occur in the original string.

Example - Using strSplit

strSplit("one,two,three", ",");

Will return the following list:

one
two
three

strSplit("name:date:time", ":");

Will return the following list:

name
date
time

strSplit("person a person b person c", "person ");

Will return the following list:

a
b
c

strStartsWith

Returns true if str starts with substr , otherwise false.

boolean strStartsWith
 ( string  str ,
 string  substr  )

Parameter	Description
`str`	String to examine
`substr`	String to look for
Returns	`true` or `false`

strSubstring

Returns a substring from a given string. The extracted substring is from position start to end .

string strSubstring
 ( string  str ,
 int  start ,
 int  end  )

Parameter	Description
`str`	The base string
`start`	Position where to start the substring extraction. Position 0 (zero) points to the first character of `str` .
`end`	Position where to end the extraction. That is, the index of the letter after the last letter in the substring.
Returns	The substring

Example - Using strSubstring

The following call returns the string "the".

strSubstring("hi there", 3, 6);

strToLower

Turns all letters in a string to lower-case.

string strToLower( string  str  )

Parameter	Description
`str`	The base string
Returns	The result string. Note, the `str` is not modified.

strToUpper

Turns all letters in a string to capital letters.

string strToUpper( string  str  )

Parameter	Description
`str`	The base string
Returns	The result string. Note, the `str` is not modified.

strTrim

Removes leading and trailing spaces from a string and returns the result.

string strTrim( string  str  )

Parameter	Description
`str`	The base string
Returns	The result string. Note, the `str` is not modified.

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