159: Mainline

The following method, for example, answers true only if the value of self is between 1200 and 1600, inclusively:

Integer method definition • instance 
inRange 
  ^ (1200 <= self) & (self <= 1600) 
Workspace
Transcript show: 1700 inRange printString; cr; 
           show: 1400 inRange printString; cr; 
           show: 1100 inRange printString. 
Transcript 
false 
true 
false 

Similarly, the show: message in the following method is sent only if the value of self is in the 1200-to-1600 range:

Integer method definition • instance 
analyzeCalories 
  (1200 <= self) & (self <= 1600) 
    ifTrue: [Transcript show: self printString; show: ' is reasonable'; cr] 
Workspace
1700 analyzeCalories. 
1400 analyzeCalories. 
1100 analyzeCalories 
Transcript 
1400 is reasonable