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diff --git a/examples/patterns/README.md b/examples/patterns/README.md deleted file mode 100644 index faf2854e..00000000 --- a/examples/patterns/README.md +++ /dev/null @@ -1,444 +0,0 @@ -# Text Pattern Matching - -As an alternative to full regular expressions, Tomo provides a limited text -matching pattern syntax that is intended to solve 80% of use cases in under 1% -of the code size (PCRE's codebase is roughly 150k lines of code, and Tomo's -pattern matching code is a bit under 1k lines of code). Tomo's pattern matching -syntax is highly readable and works well for matching literal text without -getting [leaning toothpick syndrome](https://en.wikipedia.org/wiki/Leaning_toothpick_syndrome). - -For more advanced use cases, consider linking against a C library for regular -expressions or pattern matching. - -`Pat` is a [domain-specific language](docs/langs.md), in other words, it's -like a `Text`, but it has a distinct type. - -Patterns are used in a small, but very powerful API that handles many text -functions that would normally be handled by a more extensive API: - -- [`by_pattern(text:Text, pattern:Pat -> func(->PatternMatch?))`](#by_pattern) -- [`by_pattern_split(text:Text, pattern:Pat -> func(->Text?))`](#by_pattern_split) -- [`each_pattern(text:Text, pattern:Pat, fn:func(m:PatternMatch), recursive=yes)`](#each_pattern) -- [`find_patterns(text:Text, pattern:Pat -> [PatternMatch])`](#find_patterns) -- [`has_pattern(text:Text, pattern:Pat -> Bool)`](#has_pattern) -- [`map_pattern(text:Text, pattern:Pat, fn:func(m:PatternMatch -> Text), recursive=yes -> Text)`](#map_pattern) -- [`matches_pattern(text:Text, pattern:Pat -> Bool)`](#matches_pattern) -- [`pattern_captures(text:Text, pattern:Pat -> [Text]?)`](#pattern_captures) -- [`replace_pattern(text:Text, pattern:Pat, replacement:Text, backref="@", recursive=yes -> Text)`](#replace_pattern) -- [`split_pattern(text:Text, pattern:Pat -> [Text])`](#split_pattern) -- [`translate_patterns(text:Text, replacements:{Pat,Text}, backref="@", recursive=yes -> Text)`](#translate_patterns) -- [`trim_pattern(text:Text, pattern=$Pat"{space}", left=yes, right=yes -> Text)`](#trim_pattern) - -## Matches - -Pattern matching functions work with a type called `PatternMatch` that has three fields: - -- `text`: The full text of the match. -- `index`: The index in the text where the match was found. -- `captures`: A list containing the matching text of each non-literal pattern group. - -See [Text Functions](text.md#Text-Functions) for the full API documentation. - -## Syntax - -Patterns have three types of syntax: - -- `{` followed by an optional count (`n`, `n-m`, or `n+`), followed by an - optional `!` to negate the pattern, followed by an optional pattern name or - Unicode character name, followed by a required `}`. - -- Any matching pair of quotes or parentheses or braces with a `?` in the middle - (e.g. `"?"` or `(?)`). - -- Any other character is treated as a literal to be matched exactly. - -## Named Patterns - -Named patterns match certain pre-defined patterns that are commonly useful. To -use a named pattern, use the syntax `{name}`. Names are case-insensitive and -mostly ignore spaces, underscores, and dashes. - -- `..` - Any character (note that a single `.` would mean the literal period - character). -- `digit` - A unicode digit -- `email` - an email address -- `emoji` - an emoji -- `end` - the very end of the text -- `id` - A unicode identifier -- `int` - One or more digits with an optional `-` (minus sign) in front -- `ip` - an IP address (IPv4 or IPv6) -- `ipv4` - an IPv4 address -- `ipv6` - an IPv6 address -- `nl`/`newline`/`crlf` - A line break (either `\r\n` or `\n`) -- `num` - One or more digits with an optional `-` (minus sign) in front and an optional `.` and more digits after -- `start` - the very start of the text -- `uri` - a URI -- `url` - a URL (URI that specifically starts with `http://`, `https://`, `ws://`, `wss://`, or `ftp://`) -- `word` - A unicode identifier (same as `id`) - -For non-alphabetic characters, any single character is treated as matching -exactly that character. For example, `{1{}` matches exactly one `{` -character. Or, `{1.}` matches exactly one `.` character. - -Patterns can also use any Unicode property name. Some helpful ones are: - -- `hex` - Hexidecimal digits -- `lower` - Lowercase letters -- `space` - The space character -- `upper` - Uppercase letters -- `whitespace` - Whitespace characters - -Patterns may also use exact Unicode codepoint names. For example: `{1 latin -small letter A}` matches `a`. - -## Negating Patterns - -If an exclamation mark (`!`) is placed before a pattern's name, then characters -are matched only when they _don't_ match the pattern. For example, `{!alpha}` -will match all characters _except_ alphabetic ones. - -## Interpolating Text and Escaping - -To escape a character in a pattern (e.g. if you want to match the literal -character `?`), you can use the syntax `{1 ?}`. This is almost never necessary -unless you have text that looks like a Tomo text pattern and has something like -`{` or `(?)` inside it. - -However, if you're trying to do an exact match of arbitrary text values, you'll -want to have the text automatically escaped. Fortunately, Tomo's injection-safe -DSL text interpolation supports automatic text escaping. This means that if you -use text interpolation with the `$` sign to insert a text value, the value will -be automatically escaped using the `{1 ?}` rule described above: - -```tomo -# Risk of code injection (would cause an error because 'xxx' is not a valid -# pattern name: ->> user_input := get_user_input() -= "{xxx}" - -# Interpolation automatically escapes: ->> $/$user_input/ -= $/{1{}..xxx}/ - -# This is: `{ 1{ }` (one open brace) followed by the literal text "..xxx}" - -# No error: ->> some_text.find($/$user_input/) -= 0 -``` - -If you prefer, you can also use this to insert literal characters: - -```tomo ->> $/literal $"{..}"/ -= $/literal {1{}..}/ -``` - -## Repetitions - -By default, named patterns match 1 or more repetitions, but you can specify how -many repetitions you want by putting a number or range of numbers first using -`n` (exactly `n` repetitions), `n-m` (between `n` and `m` repetitions), or `n+` -(`n` or more repetitions): - -``` -{4-5 alpha} -0x{hex} -{4 digit}-{2 digit}-{2 digit} -{2+ space} -{0-1 question mark} -``` - - -# Methods - -### `by_pattern` -Returns an iterator function that yields `PatternMatch` objects for each occurrence. - -```tomo -func by_pattern(text:Text, pattern:Pat -> func(->PatternMatch?)) -``` - -- `text`: The text to search. -- `pattern`: The pattern to match. - -**Returns:** -An iterator function that yields `PatternMatch` objects one at a time. - -**Example:** -```tomo -text := "one, two, three" -for word in text.by_pattern($Pat"{id}"): - say(word.text) -``` - ---- - -### `by_pattern_split` -Returns an iterator function that yields text segments split by a pattern. - -```tomo -func by_pattern_split(text:Text, pattern:Pat -> func(->Text?)) -``` - -- `text`: The text to split. -- `pattern`: The pattern to use as a separator. - -**Returns:** -An iterator function that yields text segments. - -**Example:** -```tomo -text := "one two three" -for word in text.by_pattern_split($Pat"{whitespace}"): - say(word.text) -``` - ---- - -### `each_pattern` -Applies a function to each occurrence of a pattern in the text. - -```tomo -func each_pattern(text:Text, pattern:Pat, fn:func(m:PatternMatch), recursive=yes) -``` - -- `text`: The text to search. -- `pattern`: The pattern to match. -- `fn`: The function to apply to each match. -- `recursive`: If `yes`, applies the function recursively on modified text. - -**Example:** -```tomo -text := "one two three" -text.each_pattern($Pat"{id}", func(m:PatternMatch): - say(m.txt) -) -``` - ---- - -### `find_patterns` -Finds all occurrences of a pattern in a text and returns them as `PatternMatch` objects. - -```tomo -func find_patterns(text:Text, pattern:Pat -> [PatternMatch]) -``` - -- `text`: The text to search. -- `pattern`: The pattern to match. - -**Returns:** -A list of `PatternMatch` objects. - -**Example:** -```tomo -text := "one! two three!" ->> text.find_patterns($Pat"{id}!") -= [PatternMatch(text="one!", index=1, captures=["one"]), PatternMatch(text="three!", index=10, captures=["three"])] -``` - ---- - -### `has_pattern` -Checks whether a given pattern appears in the text. - -```tomo -func has_pattern(text:Text, pattern:Pat -> Bool) -``` - -- `text`: The text to search. -- `pattern`: The pattern to check for. - -**Returns:** -`yes` if a match is found, otherwise `no`. - -**Example:** -```tomo -text := "...okay..." ->> text.has_pattern($Pat"{id}") -= yes -``` - ---- - -### `map_pattern` -Transforms matches of a pattern using a mapping function. - -```tomo -func map_pattern(text:Text, pattern:Pat, fn:func(m:PatternMatch -> Text), recursive=yes -> Text) -``` - -- `text`: The text to modify. -- `pattern`: The pattern to match. -- `fn`: A function that transforms matches. -- `recursive`: If `yes`, applies transformations recursively. - -**Returns:** -A new text with the transformed matches. - -**Example:** -```tomo -text := "I have #apples and #oranges and #plums" -fruits := {"apples"=4, "oranges"=5} ->> text.map_pattern($Pat'#{id}', func(match:PatternMatch): - fruit := match.captures[1] - "$(fruits[fruit] or 0) $fruit" -) -= "I have 4 apples and 5 oranges and 0 plums" -``` - ---- - -### `matches_pattern` -Returns whether or not text matches a pattern completely. - -```tomo -func matches_pattern(text:Text, pattern:Pat -> Bool) -``` - -- `text`: The text to match against. -- `pattern`: The pattern to match. - -**Returns:** -`yes` if the whole text matches the pattern, otherwise `no`. - -**Example:** -```tomo ->> "Hello!!!".matches_pattern($Pat"{id}") -= no ->> "Hello".matches_pattern($Pat"{id}") -= yes -``` - ---- - -### `pattern_captures` -Returns a list of pattern captures for the given pattern. - -```tomo -func pattern_captures(text:Text, pattern:Pat -> [Text]?) -``` - -- `text`: The text to match against. -- `pattern`: The pattern to match. - -**Returns:** -An optional list of matched pattern captures. Returns `none` if the text does -not match the pattern. - -**Example:** -```tomo ->> "123 boxes".pattern_captures($Pat"{int} {id}") -= ["123", "boxes"]? ->> "xxx".pattern_captures($Pat"{int} {id}") -= none -``` - ---- - -### `replace_pattern` -Replaces occurrences of a pattern with a replacement text, supporting backreferences. - -```tomo -func replace_pattern(text:Text, pattern:Pat, replacement:Text, backref="@", recursive=yes -> Text) -``` - -- `text`: The text to modify. -- `pattern`: The pattern to match. -- `replacement`: The text to replace matches with. -- `backref`: The symbol for backreferences in the replacement. -- `recursive`: If `yes`, applies replacements recursively. - -**Returns:** -A new text with replacements applied. - -**Example:** -```tomo ->> "I have 123 apples and 456 oranges".replace_pattern($Pat"{int}", "some") -= "I have some apples and some oranges" - ->> "I have 123 apples and 456 oranges".replace_pattern($Pat"{int}", "(@1)") -= "I have (123) apples and (456) oranges" - ->> "I have 123 apples and 456 oranges".replace_pattern($Pat"{int}", "(?1)", backref="?") -= "I have (123) apples and (456) oranges" - ->> "bad(fn(), bad(notbad))".replace_pattern($Pat"bad(?)", "good(@1)") -= "good(fn(), good(notbad))" - ->> "bad(fn(), bad(notbad))".replace_pattern($Pat"bad(?)", "good(@1)", recursive=no) -= "good(fn(), bad(notbad))" -``` - ---- - -### `split_pattern` -Splits a text into segments using a pattern as the delimiter. - -```tomo -func split_pattern(text:Text, pattern:Pat -> [Text]) -``` - -- `text`: The text to split. -- `pattern`: The pattern to use as a separator. - -**Returns:** -A list of text segments. - -**Example:** -```tomo ->> "one two three".split_pattern($Pat"{whitespace}") -= ["one", "two", "three"] -``` - ---- - -### `translate_patterns` -Replaces multiple patterns using a mapping of patterns to replacement texts. - -```tomo -func translate_patterns(text:Text, replacements:{Pat,Text}, backref="@", recursive=yes -> Text) -``` - -- `text`: The text to modify. -- `replacements`: A table mapping patterns to their replacements. -- `backref`: The symbol for backreferences in replacements. -- `recursive`: If `yes`, applies replacements recursively. - -**Returns:** -A new text with all specified replacements applied. - -**Example:** -```tomo ->> text := "foo(x, baz(1))" ->> text.translate_patterns({ - $Pat"{id}(?)"="call(fn('@1'), @2)", - $Pat"{id}"="var('@1')", - $Pat"{int}"="int(@1)", -}) -= "call(fn('foo'), var('x'), call(fn('baz'), int(1)))" -``` - ---- - -### `trim_pattern` -Removes matching patterns from the beginning and/or end of a text. - -```tomo -func trim_pattern(text:Text, pattern=$Pat"{space}", left=yes, right=yes -> Text) -``` - -- `text`: The text to trim. -- `pattern`: The pattern to trim (defaults to whitespace). -- `left`: If `yes`, trims from the beginning. -- `right`: If `yes`, trims from the end. - -**Returns:** -The trimmed text. - -**Example:** -```tomo ->> "123abc456".trim_pattern($Pat"{digit}") -= "abc" -``` |