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This is documentation for the next version of Alloy. For the latest stable release, go to the latest version.

Open source

string

The string namespace contains functions related to strings.

string.format

The string.format function produces a string by formatting a number of other values according to a specification string. It’s similar to the printf function in C, and other similar functions in other programming languages.

alloy
string.format(spec, values...)

Examples

alloy
> string.format("Hello, %s!", "Ander")
"Hello, Ander!"
> string.format("There are %d lights", 4)
"There are 4 lights"

The string.format function is most useful when you use more complex format specifications.

Specification Syntax

The specification is a string that includes formatting verbs that are introduced with the % character. The function call must then have one additional argument for each verb sequence in the specification. The verbs are matched with consecutive arguments and formatted as directed, as long as each given argument is convertible to the type required by the format verb.

By default, % sequences consume successive arguments starting with the first. Introducing a [n] sequence immediately before the verb letter, where n is a decimal integer, explicitly chooses a particular value argument by its one-based index. Subsequent calls without an explicit index will then proceed with n+1, n+2, etc.

The function produces an error if the format string requests an impossible conversion or accesses more arguments than are given. An error is also produced for an unsupported format verb.

Verbs

The specification may contain the following verbs.

VerbResult
%%Literal percent sign, consuming no value.
%tConvert to boolean and produce true or false.
%bConvert to integer number and produce binary representation.
%dConvert to integer and produce decimal representation.
%oConvert to integer and produce octal representation.
%xConvert to integer and produce hexadecimal representation with lowercase letters.
%XLike %x, but use uppercase letters.
%eConvert to number and produce scientific notation, like -1.234456e+78.
%ELike %e, but use an uppercase E to introduce the exponent.
%fConvert to number and produce decimal fraction notation with no exponent, like 123.456.
%gLike %e for large exponents or like %f otherwise.
%GLike %E for large exponents or like %f otherwise.
%sConvert to string and insert the string’s characters.
%qConvert to string and produce a JSON quoted string representation.

string.join

string.join all items in an array into a string, using a character as separator.

alloy
string.join(list, separator)

Examples

alloy
> string.join(["foo", "bar", "baz"], "-")
"foo-bar-baz"
> string.join(["foo", "bar", "baz"], ", ")
"foo, bar, baz"
> string.join(["foo"], ", ")
"foo"

string.replace

string.replace searches a string for a substring, and replaces each occurrence of the substring with a replacement string.

alloy
string.replace(string, substring, replacement)

Examples

alloy
> string.replace("1 + 2 + 3", "+", "-")
"1 - 2 - 3"

string.split

string.split produces a list by dividing a string at all occurrences of a separator.

alloy
split(list, separator)

Examples

alloy
> string.split("foo,bar,baz", "," )
["foo", "bar", "baz"]

> string.split("foo", ",")
["foo"]

> string.split("", ",")
[""]

string.to_lower

string.to_lower converts all uppercase letters in a string to lowercase.

Examples

alloy
> string.to_lower("HELLO")
"hello"

string.to_upper

string.to_upper converts all lowercase letters in a string to uppercase.

Examples

alloy
> string.to_upper("hello")
"HELLO"

string.trim

string.trim removes the specified set of characters from the start and end of a string.

alloy
string.trim(string, str_character_set)

Examples

alloy
> string.trim("?!hello?!", "!?")
"hello"

> string.trim("foobar", "far")
"oob"

> string.trim("   hello! world.!  ", "! ")
"hello! world."

string.trim_prefix

string.trim_prefix removes the prefix from the start of a string. If the string doesn’t start with the prefix, the string is returned unchanged.

Examples

alloy
> string.trim_prefix("helloworld", "hello")
"world"

string.trim_suffix

string.trim_suffix removes the suffix from the end of a string.

Examples

alloy
> string.trim_suffix("helloworld", "world")
"hello"

strings.trim_space

strings.trim_space removes any whitespace characters from the start and end of a string.

Examples

alloy
> strings.trim_space("  hello\n\n")
"hello"