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Programming-Idioms

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  • Fortran

Idiom #63 Replace fragment of a string

Assign to x2 the value of string x with all occurrences of y replaced by z.
Assume occurrences of y are not overlapping.

  character(len=:), allocatable :: x
  character(len=:), allocatable :: x2
  character(len=:), allocatable :: y,z
  integer :: j, k
  k=1
  do
     j = index(x(k:),y)
     if (j==0) then
        x2 = x2 // x(k:)
        exit
     end if
     if (j>1) then
        x2 = x2 // x(k:j+k-2)
     end if
     x2 = x2 // z
     k = k + j + len(y) - 1
  end do

This code uses reallocation on assignment for character variables. An alternative implementation might count bytes first, then allocate, then do this.

Note that _// is string concatenation in Fortran.
#include <string>
constexpr std::string ReplaceAllCopy(const std::string& x, const std::string& y, const std::string& z) {
	auto x2 = x;
	size_t i = 0;

	while (true) {
		i = x2.find(y, i);
		if (i == std::string::npos) break;
		x2.replace(i, y.length(), z);
	}
	return x2;
}

constexpr version which doesn't depend on regex
New implementation...
< > ⌨
programming-idioms.org 
  character(len=:), allocatable :: x
  character(len=:), allocatable :: x2
  character(len=:), allocatable :: y,z
  integer :: j, k
  k=1
  do
     j = index(x(k:),y)
     if (j==0) then
        x2 = x2 // x(k:)
        exit
     end if
     if (j>1) then
        x2 = x2 // x(k:j+k-2)
     end if
     x2 = x2 // z
     k = k + j + len(y) - 1
  end do
constexpr std::string ReplaceAllCopy(const std::string& x, const std::string& y, const std::string& z) {
	auto x2 = x;
	size_t i = 0;

	while (true) {
		i = x2.find(y, i);
		if (i == std::string::npos) break;
		x2.replace(i, y.length(), z);
	}
	return x2;
}
std::stringstream s;
std::regex_replace(std::ostreambuf_iterator<char>(s), x.begin(), x.end(), y, z);
auto x2 = s.str()
string x2 = x.Replace(y, z, StringComparison.Ordinal);
auto x2 = x.replace(y,z);  

var x2 = x.replaceAll(y, z);
x2 = String.replace(x, y, z)
X2 = binary:replace(X, Y, Z, [global]).
x2 := strings.ReplaceAll(x, y, z)
x2 := strings.Replace(x, y, z, -1)
allchanged [] _ _ = []
allchanged input from to = if isPrefixOf from input
  then to ++ allchanged (drop (length from) input) from to
  else head input : allchanged (tail input) from to

x2 = allchanged x y z

var x2 = x.replace(new RegExp(y, 'g'), z);
const x2 = x.replaceAll(y, z);
String x2 = x.replace(y, z);
x2 = x:gsub(y,z)
$x2 = str_replace($y, $z, $x);
x2 := StringReplace(x, y, z, [rfReplaceAll]);

my $x2 = $x =~ s/\Q$y/$z/gr;
x2 = x.replace(y, z)
x2 = x.gsub(y, z)
let x2 = x.replace(&y, &z);
Dim x2 As String = x.Replace(y, z, StringComparison.Ordinal)