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LazyEnvir : EnvironmentRedirect : Object

lazy environment
Subclasses: ProxySpace


Environment with deferred evaluation and default values.

Consequently, calculations can be done with nonexisting objects which can then be assigned later. Per default, a LazyEnvir returns instances of Maybe. See also Fdef.

NOTE: While the method put is treated as transparent and implicitly creates a placeholder, all other methods, like at, collect, do, etc. pass the placeholder. In order to retrieve the object itself, use .source - in order to reduce it to a value, use: value
e =;
e.use { ~x = ~y + ~z };\x);\x).source; // the source is a binary operation (addition on the placeholders)
e.use { ~y = 5; ~z = 7 };\x).value; // the value is 12

Class Methods

Inherited class methods

Instance Methods

.put(key, obj)

Sets the value of the reference at key.


Returns a reference to the object at key.

l = LazyEnvir.push;

// default objects are created on access
~a.value; // defaults to nil

// operations on placeholders
~c = ~a + ~b;

~c.value; // doesn't fail, instead returns nil

// variables can be assigned later
~a = 800;
~b = { 1.0.rand };


// variables can be exchanged later
~b = { 1000.rand };


Copies the environment into a new one, with each placeholder being copied as well.

.localPut(key, obj)

Sets the value of the key directly. This method is mainly used internally.


.proxyClass = value

Specify what placeholder object the environment uses by supplying a class name (Symbol). The default is a Maybe. Any object that responds to the methods source, source_ and clear can be a placeholder.

// making a pattern space using LazyEnvir

a =;


~x = Pseq([1, 2, 30], 1);
~y = Pseq([~x], inf);

z = ~y.asStream;;;;
~x = Pseq([100, 2, 300], 1);;;;



Removes the placeholder from the environment and clears it.


Returns a new placeholder object. This is used internally and can be overridden to implement other lazy environments.

Inherited instance methods