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String Replace Examples
This page was last reviewed on Feb 23, 2023.
Dot Net Perls
Replace. Programs spend their time modifying strings. Perhaps a string contains the name of an animal, but we want it to be the name of a plant.
String usage. Replace() changes the first, but also all following matching instances in the source string. A new string is returned containing the modifications.
Replace example. To start, we have a string containing the names of some animals. We replace a substring with Replace—the occurrences of "cats" are replaced with "birds."
Then We perform another replacement. We replace "and" with "or." All 3 strings are independent—strings are not modified in-place.
// Our initial string. let animals = "cats and dogs and fish" // Change "cats" to "birds." let result1 = animals.Replace("cats", "birds") // Change another word. // ... All instances of the substring are replaced. let result2 = result1.Replace("and", "or") // The three strings are separate. printfn "%s" animals printfn "%s" result1 printfn "%s" result2
cats and dogs and fish birds and dogs and fish birds or dogs or fish
Char. The Replace method can handle a single char. All instances of the char in the string are replaced with a new char. The string's length remains the same.
let code = "abcdefabc" // Use Replace to change letter "a" to underscore. let result = code.Replace('a', '_') printfn "%s" code printfn "%s" result
abcdefabc _bcdef_bc
Character array. Sometimes a replacement is too complex to be handled with a simple Replace() call. We can convert a string to a char array, and then replace characters in a for-in loop.
Array
Here We change the colon character to a lowercase letter "A." Please note multiple replacements could occur in the loop body.
Result We convert the array to a new string with the string constructor. Our replacement is complete.
let name = ":reop:gitic:" // Convert string to an array. let array = name.ToCharArray() // Change colon character to letter "A" in string. for c in 0 .. array.Length - 1 do if array.[c] = ':' then array.[c] <- 'a' // Convert char array to string. let resultCopy = new string(array) printfn "%s" resultCopy
areopagitica
Some notes. The string type in F# offers other methods that change strings. For example, Insert and Remove are similar to Replace.
String
A common string operation. Strings are used throughout programs. And with the Replace method from the .NET Framework, we swap string fragments in a standard, optimized way in this language.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
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