String operations

"[" ++ implode(", ", contents) ++ "]"

substring(0, length(s) - 1, s)

String literals are written in double quotes, and give the standard special meaning to the following escape characters:

\\ \r \n \t

There is one special operator that applies to strings, the append operator:

<Expr> ++ <Expr>

Silver will efficiently evaluate string appends, so this is the standard method of composing strings together.

In addition there is a special function for determining lengths that works with strings:

length ( <Expr> )

All of the following string manipulation function are in the core library. For absolutely up-to-date documentation, you can see String.sv in core, distributed with Silver.

function implode
String ::= sep::String lst::[String]

Fold a list of strings (lst) into one string, by interspersing a separator (sep).

Example:

implode(", ", ["Hello", "World!"])

will produce the string "Hello, World!".

function explode
[String] ::= sep::String str::String

Split a string (str) into a list of strings by a separator (sep). If the separator is the empty string then the string is split into single character strings.

Example:

explode("/", "/path/to/file")

will produce the list of strings ["", "path", "to", "file"].

function indexOf
Integer ::= needle::String haystack::String

Find the index of a needle in the haystack. (Indices are 0-based.) Or -1 if not found.

Example:

indexOf("/", "/path/file")

will produce the integer 0.

indexOf("/", "C:\path\file")

will produce the integer -1.

function lastIndexOf
Integer ::= needle::String haystack::String

Find the LAST index of a needle in the haystack. (Indices are 0-based.) Or -1 if not found.

Example:

lastIndexOf("/", "/path/file")

will produce the integer $5$.

lastIndexOf("/", "C:\path\fil")

will produce the integer $-1$.

function substring
String ::= start::Integer endl::Integer str::String

Return a substring of the original. Indices are 0-based. The first index is inclusive, but the last index is exclusive.

Example:

substring(1, 5, "/path/file")

will produce the string \texttt{“path”}.

-- with str = "/path/file"
substring(indexOf("/", str) + 1, lastIndexOf("/", str), str)

will produce the string "path".

function startsWith
Boolean ::= pre::String s::String

function endsWith
Boolean ::= post::String s::String

Tests if one string is a prefix (or suffix) of another string s.

function isDigit
Boolean ::= str::String

(All of these functions have the same signature.)

Tests if all characters of a string are digits (or letters, whitespace, uppercase, or lowercase.) May in practice be Unicode aware, but this behavior hasn’t quite been finalized yet.