Environment : IdentityDictionary {
	classvar <>stack;	
	
	*make { arg function;
		^this.new.make(function)
	}
	*use { arg function;
		^this.new.use(function)
	}

	make { arg function;
		// pushes the Envir, executes function, returns the Envir
		// usually used to create an environment by adding new variables to it.
		var result, saveEnvir;
		
		saveEnvir = currentEnvironment;
		currentEnvironment = this;
		protect {
			function.value(this);
		}{
			currentEnvironment = saveEnvir;
		};
	}
	use { arg function;
		// temporarily replaces the currentEnvironment with this, 
		// executes function, returns the result of the function
		var result, saveEnvir;
		
		saveEnvir = currentEnvironment;
		currentEnvironment = this;
		protect {
			result = function.value(this);
		}{
			currentEnvironment = saveEnvir;
		};
		^result
	}
	
	eventAt { arg key; ^this.at(key) }
	composeEvents { arg event; ^this.copy.putAll(event) }
	
	*pop {
		if(stack.notNil and: { stack.notEmpty }) { currentEnvironment = stack.pop };
	}
	*push { arg envir;
		stack = stack.add(currentEnvironment);
		currentEnvironment = envir;
	}
	pop { ^this.class.pop }
	push { this.class.push(this) }
	
	linkDoc { arg doc, pushNow = true;
     	doc = doc ? Document.current;
     	doc.envir_(this);
     	if(pushNow and: { currentEnvironment !== this }) { this.push };
     }
     
     unlinkDoc { arg doc, popNow = false;
     	doc = doc ? Document.current;
     	if(doc.envir === this) { doc.envir_(nil) };
     	if(popNow and:  { currentEnvironment === this }) { this.pop };
     }

}

