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--- status: Rewritten July 2020
--- author(s): Lily Silverstein, Mahrud
--- notes: functions below are all defined in regex.m2
doc ///
Node
Key
separate
(separate, String)
(separate, String, String)
(separate, String, ZZ, String)
[separate, POSIX]
"separateRegexp"
Headline
split a string into substrings using a regular expression
Usage
separate str
separate(re, str)
separate(re, n, str)
Inputs
re:String
a @TO2 {"regular expressions", "regular expression"}@ describing a pattern
str:String
the string to split
n:ZZ
the index of the parenthesized expression to split on
POSIX=>Boolean
if true, interpret the @TT "re"@ using the POSIX Extended flavor, otherwise the Perl flavor
Outputs
:List
a list of strings obtained by breaking @TT "str"@ at every match to the pattern @TT "re"@, or, if a natural
number @TT "n"@ is specified, using the $n$-th parenthesized expression in @TT "re"@ as the separator.
If no @TT "re"@ is specified, @TT "str"@ is split at every new line.
Description
Text
For an introduction to regular expressions, see @TO "regular expressions"@.
Example 1: The command @TT "separate(s)"@ breaks the string at every occurrence of @TT "\\r\\n"@ or @TT "\\n"@.
Example
s = "A string with both Unix-style\nand Windows-style\r\nnew line characters."
separate s
Text
This is equivalent to using the @TO lines@ function.
Example
lines s
Text
Example 2: use commas, periods, and semicolons as separators.
Example
separate("[,.;]", "Example: a string. That, is punctuated, weirdly; for demonstration purposes.")
Text
Example 3: match any number of consecutive spaces.
Example
t = separate("[ ]+", "this string has different lengths of spacing between words")
Text
We can now correct the original string using the @TO demark@ and @TO replace@ functions.
Example
replace("has", "does not have", demark(" ", t))
Text
Example 4: delete every word starting with "x" from a string, by using @TO concatenate@ together with @TO separate@.
Example
s = "algng xjfr kfjxse xhgfj xooi xwj kvexr anvi endj xkfi";
concatenate separate(" x[A-Za-z]*", s)
Text
Example 5:
The optional argument @TT "n"@ allows us to specify a separator that differs from the match criteria.
In the previous example, words beginning with "x" were both the match and the separator.
In this example, we match words beginning with "x", but separate the string using the leading "x".
With @TO concatenate@, this results in deleting just the "x" from words starting with "x"
(not the same as removing every "x").
Example
concatenate separate(" (x)[A-Za-z]*", 1, s)
Text
@TT "separateRegexp"@ is a deprecated synonym for @TT "separate"@.
Caveat
For backwards compatibility, if the pattern is a single character and it is an unescaped special character,
such as @TT "+"@, @TT "*"@, or @TT "."@, then it is treated as a literal character. In future code, the pattern
must be escaped.
SeeAlso
"regular expressions"
"strings and nets"
regex
lines
demark
concatenate
Node
Key
lines
(lines, String)
(lines, String, String)
Headline
split a string into lines
Usage
lines s
lines(nl, s)
Inputs
s:String
nl:String
Outputs
:List
an array of strings obtained from the string @TT "s"@ by breaking
it at the characters specified by the string @TT "nl"@
Description
Text
The form @TT "lines s"@ is designed to break lines correctly when the file
follows the Unix or MS-DOS convention. In other words, it will break a line
at @TT "\\r\\n"@ or @TT "\\n"@.
Example
lines "a\nb\nc\n"
peek oo
lines "a\nb\nc\nd"
peek oo
lines( "\\.", "a.b.c." )
peek oo
lines( "\\.", "a.b.c.d" )
peek oo
Caveat
For backwards compatibility, if the pattern is a single character and it is an unescaped special character,
such as @TT "+"@, @TT "*"@, or @TT "."@, then it is treated as a literal character. In future code, the pattern
must be escaped.
SeeAlso
"newline"
separate
///
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