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--- status: Rewritten July 2020
--- author(s): Dan, Mahrud
--- notes:
doc ///
Key
replace
Headline
replacement in strings and lists
Subnodes
(replace, ZZ, Thing, BasicList)
///
doc ///
Key
(replace, String, String, String)
[(replace, String, String, String), POSIX]
Headline
replace substrings matching a regular expression
Usage
replace(re, replacement, str)
Inputs
re:String
a @TO2 {"regular expressions", "regular expression"}@ describing a pattern
replacement:String
following the @TO2 {"regular expressions", "formatting syntax"}@
str:String
a subject string to be processed
POSIX=>Boolean
if true, interpret the @TT "re"@ using the POSIX Extended flavor, otherwise the Perl flavor
Outputs
:String
obtained from @TT "str"@ by replacing its substrings matching @TT "re"@ by copies of @TT "replacement"@
Description
Text
For an introduction to regular expressions, see @TO "regular expressions"@.
Example
replace("[a-z]+", "x", "Dog cat cat.")
Text
The @TT "replacement"@ string may contain @TO2 {"regular expressions", "formatting syntax"}@
such as backreferences @TT "$1"@ or @TT "\\\\1"@, which will be replaced by the string matching
the corresponding parenthesized subexpression of @TT "re"@.
Example
replace("(\\w+)\\.?", "A \\1.", "Dog cat cat.")
Text
Special operators such as the lowercase operator @TT "\\\\L"@ may also be used to manipulate the
replacement substring.
Example
replace("(\\w+)\\.?", "A \\L$1.", "Dog cat cat.")
Text
Lookaheads and lookbehinds can be used to precisely control the regular expression matches.
Example
s = "catfish cats dogs";
replace("cat(?!fish)s?", "\\U$&", s)
replace("\\w+(?=s\\b)", "\\U$&", s)
s = "goldfish swordfish catfish catdog";
replace("\\w+(?=fish)", "\\U$&", s)
replace("(?<=cat)\\w+", "\\U$&", s)
Text
The @TT "POSIX => true"@ option can be used to specify the POSIX Extended flavor for the regular
expression used to match. Note that only the Perl flavor allows the use of lookaheads and lookbehinds.
SeeAlso
"regular expressions"
"strings and nets"
regex
match
separate
(select, String, String, String)
///
doc ///
Key
(replace, ZZ, Thing, BasicList)
Headline
copy a list, replacing an element
Usage
s = replace(i, t, l)
Inputs
i:ZZ
t:Thing
l:BasicList
Outputs
s:BasicList
a copy of the list @TT "l"@ in which @TT "t"@ has replaced the element at position @TT "i"@.
Description
Text
A negative value of @TT "i"@ is taken relative to the end of the list.
Example
replace(4, t, 0..10)
replace(0, t, 0..10)
replace(10, t, 0..10)
replace(-1, t, 0..10)
replace(-11, t, 0..10)
///
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