Basic Postconditionals

This Lesson is estimated to be completed in 20 minutes.

You should have first completed the Lessons:

• Basic Coding Style
• Basic Code Life Cycle

Description

Postconditionals are one of the rather unique features of the M language.

They are logical conditions that are appended to M Commands using the ”:” symbol, and that determine whether the command will be executed or not.

They follow the basic structure

command:condition

as in

quit:(i>10)

where the quit command will be executed if i is larger than 10

Postconditionals are place between the command and its arguments.

For example

write:(i>10) "More than 10 iterations",!

will write the message only if i is larger than 10.

and

set:(a<b) s=a

will set s to the value of a only if a is less than b.

Next Lesson: Basic Scope