5.7: Chapter Summary
- Page ID
- 40108
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- A message is always sent to an object named the receiver, which itself may be the result of other message sends.
- There are three types of messages: unary, binary, and keyword.
- Unary messages are messages that do not require any argument. They are of the form of
receiver selector
. - Binary messages are messages that involve two objects, the receiver and another object, whose selector is composed of one or more characters from the following list: +, -, *, /, |, &, =, >, <, ~, and @. They are of the form:
receiver selector argument
. - Keyword messages are messages that involve more than one object and that contain at least one colon character (:). They are of the form:
receiver selectorWordOne: argumentOne wordTwo: argumentTwo
. - Rule One. Unary messages are sent first, then binary messages, and finally keyword messages.
- Rule Two. Messages in parentheses are sent before any others.
- Rule Three. When the messages are of the same type, the order of evaluation is from left to right.
- In Pharo, traditional arithmetic operators such as + and * have the same priority. + and * are just binary messages, therefore * does not have priority over +. You must use parentheses to obtain the desired arithmetical order of operations.