5.6.12 Data type validation for fields

These functions set a field to be able to contain only a certain type of input. The user will not be able to move off the field if it contains invalid input.

Procedure: set-field-type! field type …

Procedure: field-type field

The procedure set-field-type! declares a data type for a given form field. The procedure field-type returns the declared data type. The input type is a symbol that is one of the following list. This is the type checked by validation functions. The predefined types are as follows:

TYPE_ALNUM

Alphanumeric data. Requires a third int argument, a minimum field width.

TYPE_ALPHA

Character data. Requires a third int argument, a minimum field width.

TYPE_ENUM

Accept one of a specified set of strings. Requires a third argument pointing to a list of strings; a fourth integer flag argument to enable case-sensitivity; and a fifth int flag argument specifying whether a partial match must be a unique one (if this flag is off, a prefix matches the first of any set of more than one list elements with that prefix). Please notice that the string list is not copied, only a reference to it is stored in the field. So you should avoid using a list that lives in automatic variables on the stack.

TYPE_INTEGER

Integer data. Requires a third int argument controlling the precision, a fourth long argument constraining minimum value, and a fifth long constraining maximum value. If the maximum value is less than or equal to the minimum value, the range is simply ignored.

TYPE_NUMERIC

Numeric data (may have a decimal-point part). Requires a third int argument controlling the precision, a fourth double argument con- straining minimum value, and a fifth double constraining maximum value. If your system supports locales, the decimal point character to be used must be the one specified by your locale. If the maximum value is less than or equal to the minimum value, the range is simply ignored.

TYPE_REGEXP

Regular expression data. Requires a regular expression (char *) third argument; the data is valid if the regular expression matches it. Regular expressions are in the format of regcomp and regexec. Please notice that the regular expression must match the whole field. If you have for example an eight character wide field, a regular expression "^[0-9]*$" always means that you have to fill all eight positions with digits. If you want to allow fewer digits, you may use for example "^[0-9]* *$" which is good for trailing spaces (up to an empty field), or "^ *[0-9]* *$" which is good for leading and trailing spaces around the digits.

TYPE_IPV4

An Internet Protocol Version 4 address. This requires no additional argument. It is checked whether or not the buffer has the form a.b.c.d, where a,b,c and d are numbers between 0 and 255. Trailing blanks in the buffer are ignored. The address itself is not validated. Please note that this is an ncurses extension. This field type may not be available in other curses implementations.