String functions (programming)
From Wikipedia, the free encyclopedia
String functions are used in computer programming languages to manipulate a string or query information about a string (some do both).
Most computer programming languages that have a string datatype will have some string functions although it should be noted that there may be other low level ways within each language to handle strings directly. In object oriented languages, string functions are often implemented as properties and methods of string objects.
The most basic example of a string function is the length(string) function. This function returns the length of a string literal.
eg. length("hello world") would return 11.
Other languages may have string functions with similar or exactly the same syntax or parameters or outcomes. For example in many languages the length function is usually represented as len(string). The below list of common functions aims to help limit this confusion.
Contents |
[edit] Common String Functions (multi language reference)
Here is a list of common string functions which are found in other languages. Any other equivalent functions used by other languages are also listed. The below list of common functions aims to help programmers find the equivalent function in a language. Note, string concatenation and regular expressions are handled in separate pages.
[edit] index
see #instr
[edit] instr
| Other names | index, locate |
| Definition | instr(string,substring) returns integer |
| Description | Returns the position of the start of the first occurrence of substring in string. If the substring is not found returns 0. |
| Related | instrrev |
| Format | Languages |
|---|---|
| instr([startpos,]string,substring) | VB (startpos optional) |
| index(string,substring) | Awk |
| index(string,substring[,startpos]) | Perl |
| locate(string, substring) | Ingres (if not found returns string length + 1) |
| strstr(string, substring) | C |
| string.find(substring) | C++ |
| pos(substring, string) | Delphi |
| string.index(substring) | Python, Ruby |
' Example in VB instr("Hello mate", "ell") ' would return 2 instr(5, "Hello mate", "e") ' would return 10 instr("word", "z") ' would return 0.
[edit] left
| Other names | left, substr |
| Definition | left(string,n) returns string |
| Description | Returns the left n part of a string. If n is greater than the length of the string then the whole string is returned. |
| Format | Languages |
|---|---|
| left(string,n) | VB, Ingres |
| substr(string, 0, n) | Awk (changes string), Perl |
| string[:n] | Python |
| string[0..n] | Ruby |
| string.substr(0,n) | C++ |
| leftstr(string, n) | Delphi |
' Example in VB left("sandroguidi", 3) would return the string "san". left("sandroguidi", 100) would return the string "sandroguidi".
[edit] len
see #length
[edit] length
| Other names | len, length |
| Definition | length(string) returns an integer number |
| Description | Returns the length of a string (not counting the null terminator or any other of the string's internal structural information). An empty string returns a length of 0. |
| Format | Languages |
|---|---|
| length(string) | Perl, Ingres, Delphi |
| len(string) | VB, Python |
| string.size or string.length |
Ruby |
| strlen(string) | C |
| string.length() | C++ |
# Examples in Perl length("hello") returns 5. length("") returns 0.
[edit] locate
see #instr
[edit] mid
see #substring
[edit] replace
| Other names | sed |
| Definition | replace(string, find, replace) returns string |
| Description | Returns a string the with find occurrences changed to replace. |
| Format | Languages |
|---|---|
| replace(string, find, replace) | VB |
| string.replace(find, replace) | Python |
| string.gsub(find, replace) | Ruby |
| echo "string" | sed 's/find/replace/g' | Unix |
' Examples in VB replace("effffff","f","jump") returns ejumpjumpjumpjumpjumpjump replace("blah", "z","y") returns blah.
[edit] slice
see #substring
[edit] strip
see #trim
[edit] strcmp
| Other names | compare |
| Definition | strcmp(a:string,b:string) returns the equivalent of a-b. |
| Description | Compares two strings to each other, if they equals textually, returns zero. If a is "textually bigger" returns a positive number and returns a negative number otherwise. |
[edit] substring
| Other names | mid, substr, slice |
| Definition | substr(string, startpos, offset) returns string |
| Description | Returns a substring of string starting at startpos of length offset. If offset goes past the end of the string then only the string form startpos to end of string is returned. |
| Format | Languages |
|---|---|
| mid(string, startpos, offset) | VB |
| substr(string, startpos, offset) | Awk (changes string), Perl |
| string[startpos:endpos] | Python (endpos = startpos + offset) |
| string[startpos, offset] | Ruby |
| string.slice(startpos, endpos) | JavaScript |
| string.substr(startpos, length) | C++ |
| copy(string, startpos, length) | Delphi |
Examples in Awk substr("abc", 2,1) returns "b". substr("abc", 2,100) returns "bc".
[edit] uppercase
| Other names | UCASE, toupper, upper, upcase |
| Definition | uppercase(string) returns string |
| Description | Returns the string in upper case. |
| Format | Languages |
|---|---|
| UCASE(string) | VB |
| toupper(string) | Awk (changes string), Perl |
| toupper(char) | C |
| transform (string.begin(), string.end(), string.begin(), toupper) | C++ |
| uppercase(string) | Delphi |
| echo "string" | tr 'a-z' 'A-Z' | Unix |
| string.upper() | Python |
| string.upcase | Ruby |
Example in VB Ucase("Wiki means fast?") would print "WIKI MEANS FAST?".
[edit] trim
- see Trim (programming).
trim or strip is used to remove whitespace from the beginning, end, or both beginning and end, of a string.
[edit] Concatenation
Joining two strings together is called concatenation. Some languages support this natively in the language (VB) and some do not (C).
