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195 lines
5.9 KiB
Markdown
195 lines
5.9 KiB
Markdown
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# Extensions
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CEL extensions are a related set of constants, functions, macros, or other
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features which may not be covered by the core CEL spec.
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## Encoders
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Encoding utilies for marshalling data into standardized representations.
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### Base64.Decode
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Decodes base64-encoded string to bytes.
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This function will return an error if the string input is not
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base64-encoded.
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base64.decode(<string>) -> <bytes>
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Examples:
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base64.decode('aGVsbG8=') // return b'hello'
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base64.decode('aGVsbG8') // error
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### Base64.Encode
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Encodes bytes to a base64-encoded string.
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base64.encode(<bytes>) -> <string>
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Example:
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base64.encode(b'hello') // return 'aGVsbG8='
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## Strings
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Extended functions for string manipulation. As a general note, all indices are
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zero-based.
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### CharAt
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Returns the character at the given position. If the position is negative, or
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greater than the length of the string, the function will produce an error:
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<string>.charAt(<int>) -> <string>
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Examples:
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'hello'.charAt(4) // return 'o'
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'hello'.charAt(5) // return ''
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'hello'.charAt(-1) // error
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### IndexOf
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Returns the integer index of the first occurrence of the search string. If the
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search string is not found the function returns -1.
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The function also accepts an optional position from which to begin the
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substring search. If the substring is the empty string, the index where the
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search starts is returned (zero or custom).
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<string>.indexOf(<string>) -> <int>
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<string>.indexOf(<string>, <int>) -> <int>
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Examples:
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'hello mellow'.indexOf('') // returns 0
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'hello mellow'.indexOf('ello') // returns 1
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'hello mellow'.indexOf('jello') // returns -1
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'hello mellow'.indexOf('', 2) // returns 2
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'hello mellow'.indexOf('ello', 2) // returns 7
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'hello mellow'.indexOf('ello', 20) // error
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### LastIndexOf
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Returns the integer index of the last occurrence of the search string. If the
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search string is not found the function returns -1.
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The function also accepts an optional position which represents the last index
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to be considered as the beginning of the substring match. If the substring is
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the empty string, the index where the search starts is returned (string length
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or custom).
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<string>.lastIndexOf(<string>) -> <int>
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<string>.lastIndexOf(<string>, <int>) -> <int>
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Examples:
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'hello mellow'.lastIndexOf('') // returns 12
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'hello mellow'.lastIndexOf('ello') // returns 7
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'hello mellow'.lastIndexOf('jello') // returns -1
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'hello mellow'.lastIndexOf('ello', 6) // returns 1
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'hello mellow'.lastIndexOf('ello', -1) // error
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### LowerAscii
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Returns a new string where all ASCII characters are lower-cased.
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This function does not perform Unicode case-mapping for characters outside the
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ASCII range.
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<string>.lowerAscii() -> <string>
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Examples:
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'TacoCat'.lowerAscii() // returns 'tacocat'
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'TacoCÆt Xii'.lowerAscii() // returns 'tacocÆt xii'
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### Replace
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Returns a new string based on the target, which replaces the occurrences of a
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search string with a replacement string if present. The function accepts an
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optional limit on the number of substring replacements to be made.
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When the replacement limit is 0, the result is the original string. When the
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limit is a negative number, the function behaves the same as replace all.
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<string>.replace(<string>, <string>) -> <string>
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<string>.replace(<string>, <string>, <int>) -> <string>
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Examples:
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'hello hello'.replace('he', 'we') // returns 'wello wello'
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'hello hello'.replace('he', 'we', -1) // returns 'wello wello'
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'hello hello'.replace('he', 'we', 1) // returns 'wello hello'
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'hello hello'.replace('he', 'we', 0) // returns 'hello hello'
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### Split
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Returns a list of strings split from the input by the given separator. The
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function accepts an optional argument specifying a limit on the number of
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substrings produced by the split.
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When the split limit is 0, the result is an empty list. When the limit is 1,
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the result is the target string to split. When the limit is a negative
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number, the function behaves the same as split all.
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<string>.split(<string>) -> <list<string>>
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<string>.split(<string>, <int>) -> <list<string>>
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Examples:
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'hello hello hello'.split(' ') // returns ['hello', 'hello', 'hello']
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'hello hello hello'.split(' ', 0) // returns []
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'hello hello hello'.split(' ', 1) // returns ['hello hello hello']
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'hello hello hello'.split(' ', 2) // returns ['hello', 'hello hello']
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'hello hello hello'.split(' ', -1) // returns ['hello', 'hello', 'hello']
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### Substring
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Returns the substring given a numeric range corresponding to character
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positions. Optionally may omit the trailing range for a substring from a given
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character position until the end of a string.
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Character offsets are 0-based with an inclusive start range and exclusive end
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range. It is an error to specify an end range that is lower than the start
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range, or for either the start or end index to be negative or exceed the string
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length.
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<string>.substring(<int>) -> <string>
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<string>.substring(<int>, <int>) -> <string>
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Examples:
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'tacocat'.substring(4) // returns 'cat'
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'tacocat'.substring(0, 4) // returns 'taco'
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'tacocat'.substring(-1) // error
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'tacocat'.substring(2, 1) // error
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### Trim
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Returns a new string which removes the leading and trailing whitespace in the
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target string. The trim function uses the Unicode definition of whitespace
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which does not include the zero-width spaces. See:
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https://en.wikipedia.org/wiki/Whitespace_character#Unicode
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<string>.trim() -> <string>
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Examples:
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' \ttrim\n '.trim() // returns 'trim'
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### UpperAscii
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Returns a new string where all ASCII characters are upper-cased.
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This function does not perform Unicode case-mapping for characters outside the
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ASCII range.
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<string>.upperAscii() -> <string>
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Examples:
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'TacoCat'.upperAscii() // returns 'TACOCAT'
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'TacoCÆt Xii'.upperAscii() // returns 'TACOCÆT XII'
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