splitStringBy

lib.strings.splitStringBy

Docs pulled from | This Revision | about 1 hour ago

Splits a string into substrings based on a predicate that examines adjacent characters.

This function provides a flexible way to split strings by checking pairs of characters against a custom predicate function. Unlike simpler splitting functions, this allows for context-aware splitting based on character transitions and patterns.

Inputs

predicate: Function that takes two arguments (previous character and current character) and returns true when the string should be split at the current position. For the first character, previous will be "" (empty string).
keepSplit: Boolean that determines whether the splitting character should be kept as part of the result. If true, the character will be included at the beginning of the next substring; if false, it will be discarded.
str: The input string to split.

Return

A list of substrings from the original string, split according to the predicate.

Type

splitStringBy :: (string -> string -> bool) -> bool -> string -> [string]

Examples

`lib.strings.splitStringBy` usage example

Split on periods and hyphens, discarding the separators:

splitStringBy (prev: curr: builtins.elem curr [ "." "-" ]) false "foo.bar-baz"
=> [ "foo" "bar" "baz" ]

Split on transitions from lowercase to uppercase, keeping the uppercase characters:

splitStringBy (prev: curr: builtins.match "[a-z]" prev != null && builtins.match "[A-Z]" curr != null) true "fooBarBaz"
=> [ "foo" "Bar" "Baz" ]

Handle leading separators correctly:

splitStringBy (prev: curr: builtins.elem curr [ "." ]) false ".foo.bar.baz"
=> [ "" "foo" "bar" "baz" ]

Handle trailing separators correctly:

splitStringBy (prev: curr: builtins.elem curr [ "." ]) false "foo.bar.baz."
=> [ "foo" "bar" "baz" "" ]

Noogle detected

Aliases

lib.splitStringBy

Implementation

The following is the current implementation of this function.

splitStringBy =
    predicate: keepSplit: str:
    let
      len = stringLength str;

      # Helper function that processes the string character by character
      go =
        pos: currentPart: result:
        # Base case: reached end of string
        if pos == len then
          result ++ [ currentPart ]
        else
          let
            currChar = substring pos 1 str;
            prevChar = if pos > 0 then substring (pos - 1) 1 str else "";
            isSplit = predicate prevChar currChar;
          in
          if isSplit then
            # Split here - add current part to results and start a new one
            let
              newResult = result ++ [ currentPart ];
              newCurrentPart = if keepSplit then currChar else "";
            in
            go (pos + 1) newCurrentPart newResult
          else
            # Keep building current part
            go (pos + 1) (currentPart + currChar) result;
    in
    if len == 0 then [ (addContextFrom str "") ] else map (addContextFrom str) (go 0 "" [ ]);