### 4.22.2 string expressions

A string expression is:

1. a sequence of characters between two unescaped quotes (`"`)
2. an identifier of type string
3. a function returning string
4. a substring (using the bracket operator)
5. a type cast to string (see string type cast)
6. string expressions combined by the operation `+`.

Example:

    // string_expression[start, length] : a substring
    // (possibly filled up with blanks)
    // the substring of s starting at position 2
    // with a length of 4
    string s="123456";
    s[2,4];
    ==> 2345
    "abcd"[2,2];
    ==> bc
    // string_expression[position] : a character from a string
    s[3];
    ==> 3
    // string_expression[position..position] :
    // a substring starting at the first position up to the second
    // given position
    s[2..4];
    ==> 2 3 4
    // a function returning a string
    typeof(s);
    ==> string

See Type conversion and casting

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