<Form Input>

Form input table

element	type	name	value	submits	multiplicity	return type


<input>	button			no	no	basic
<input>	checkbox			no	yes	list { value }
<input>	file		-	no	no	basic/tuple `*`
<input>	hidden			no	no	basic
<input>	image		-	yes	no	tuple { x, y }

<input>	password			no	no	basic
<input>	radio			no	yes	basic
<input>	reset	-		no	-	-
<input>	submit	C		yes	yes	basic
<input>	text			no	no	basic

<textarea>				no	no	basic
<select>			-	no	no	basic
<select multiple>			-	no	no	list { value }
<tuple>**			-	no	yes	list { ... }
<continue>**		C		yes	yes	basic

	Attribute required.
	Attribute optional.
C	The name is implicitly "continue".
*)	The file input field may return a tuple with three strings named `filename`, `content`, and `type`.
**)	These elements are special to `<bigwig>`. They are not part of standard HTML. They are compiled to other elements and JavaScript; The client never sees these elements.

multiplicity: Multiple input elements allowed with the same name (value of the name attribute).
basic: Can be either: bool, int, float, char, string, and time. An implicit coercion from type string will take place.
list: Can be either a vector or a relation, with schemas containing the mentioned attribute names (all of which are of basic type).

button: Straightforward.
checkbox: Multiple checkboxes with the same name is allowed, they will together return a list with the values of all the boxes checked.
file: May be received as either a string or a tuple with three strings named filename, content, and type. In the former case, the value received will be the name of the file the client selected. In the latter case, the tuple three fields will respectively receive the name of the file, the contents of the file, and the mime type of the file.
hidden: Straightforward.
image: Will return the x and y coordinates of the point clicked in the image as a tuple with two attributes "x" and "y". The click will cause the page to be submitted.
password: The text field always returns a basic type and is required to have a name attribute. If a value attribute is supplied, this will be the text initially present in the field.
radio: Multiple radio buttons with the same name is allowed, but as in HTML only one of them will be returned.
reset: Will cause the form to reset.
submit: Will submit the form.
text: text is the default type for form input elements. The text field always returns a basic type and is required to have a name attribute. If a value attribute is supplied, this will be the text initially present in the field.
<textarea>: Straightforward.
<select>: If the "multiple" attribute is present, the field will return a list of the options selected. If not, it will return the option selected as a basic value.
<tuple>: The tuple input field allows information of dynamically varying size to be received and collated into vectors or a relations on the server-side. Tuples baring the same name are viewed as a single input field. This extension allows multiple occurrences of the same input field name to appear in a document. When the field values are received, they are automatically transformed into tuples in a vector or a relation with corresponding schema. Since <bigwig> does not have support for higher-order relations, tuples cannot be nested.
<continue>: The continue field is added as a convenient way of submitting values. A continue field cannot have a name, instead the keyword continue is available for value reception in (show-)receive statements. The value attribute is optional, but must be received if present. The continue field has two variants "type=button" and "type=anchor" (default), controlling the appearance of the submission field. That is, whether it should be a button or a text hyperlink. The continue field is compiled into a button or an HTML anchor with embedded JavaScript that will take care of submitting the form when clicked.
Note: This will only work for JavaScript enabled browsers.

bigwig@brics.dk
Last updated: November 2, 2001