Water 5-Common Data Types-Generic Object and Collection

Contract
Return type	wob
No input parameters.
Parameter kind	Default value	Type
Other unkeyed arguments	opt with ekind of expression	wob
Other keyed arguments	opt

Water Contract
<method set _other_keyed=opt=wob=ekind.code="_add_to_environment" _other_unkeyed=opt=wob=ekind.expression="_body"/>

See also: set_value, active_value

set is the main way to make an assignment, i.e. to assign a value to a local variable or field. set is similar to set_value but it can set multiple variables using the key=value syntax.

Example: Set a field in an object

thing.<set acolor="red" weight=2.<plus 3/> />
thing.acolor

"red"

thing.weight

5

set with a regular object as _subject cannot have a content.

Set a Local Variable

set with no _subject can have a content. The variables will be local variables and will be bound lexically during the execution of the code in the body of the set .

Example:

<set a=1 b=2>  a.<plus b/> </set>

If you do not give a content to a subjectless call to set, it will set the given keys as local variables in the current lexical scope:

<method foo> 
 <set a=2 b=3/> a.<plus b/> 
</method>
<foo/>

Set a fluid variable

If _subject is fluid then the vars bound will be fluid vars and there must be a content. During the dynamic extend of the execution of the content, (that means all the lexical code, plus anything that it calls, recursively on down) the variable will be bound to the values set. To reference them you must prefix the variable name with 'fluid'.

<method adjust factor=req>  fluid.x.<times factor/> </>
fluid.<set x=5>
       fluid.x.<plus <adjust 10/> />
   </set>

Which is equivalent to: fluid.x.<plus fluid.x.<times factor/>/> which is:

5.<plus 5/>.<times 10/>

100

The secret is that fluid.x in the 'adjust' method executes to 5 even though it was set outside the body of the adjust method. When our call to fluid.<set x=5> x </set> returns, then the value of fluid.x is changed to what it was before the call to fluid.<set x=5> x </set> which will be unbound if we hadn't previous wrapped the dynamically executing code in fluid.<set x=foo> x </set> Thus each call to fluid.<set x=foo> x </set> will shadow the previous value of fluid.x until the call to set returns.

The Returned Value

set returns _subject i.e. the container which has the variable being set. If there is no subject and no content, set returns null.

Example: when setting local variables, set returns null
<set a=2 b=3/>

null

If there is a content, set returns the value of the last expression.

Example:
<set a=2 b=3> b a </>

2

Example:

fluid.<set a=2 b=3> fluid.b fluid.a </>