Pseudocode reference

This page explains how to interpret the pseudocode that appears in some pages.

Motivation

The principles behind the pseudocode are:

• Be easily readable
• Express what is essential
• Leave freedom of expression, i.e., avoid strict rules

What are the advantages? Pseudocode:

• is more compact than human language
• does not tie the algorithm to any programming language
• contains fewer details than source code and therefore:
  • pseudocode is faster to write
  • it's easier to see the overall picture from pseudocode

Comments

// This is a comment

Variables and strings

// Declaring a string variable:
my_var = "Example string"

// Concatenation happens as follows.
// This will result in "Example string is nice"
my_var_longer = my_var + " is nice"

Calculation (calc)

// "calc result" indicates that the component generates a result to be published.
// Often, this includes calculation (such as simulation)
// but the component may as well supply a constant value.
calc result

Messaging (publ, recv)

// The component receives a message with some input to calculation.
// This does not specify where the input comes from.
recv input

// Use the input to calculate a result.
calc result

// Publish the result.
// This does not specify the topic to which the result is published.
publ result

Often, pseudocode does not specify to which topic to publish. This is to avoid redundancy with another page or location that specifies the exact topic. However, if there is a need to specify the topic explicitly, you can say:

topic = "TopicX"
publ result to topic

// Alternatively:
publ result to "TopicX"

If conditions (if, else)

// Indentation indicates which lines belong to which code block (if and else).
if x
  // This line is executed if condition "x" matches
else if y
  // This line is executed if condition "y" matches
else
  // This line is executed if none of the earlier conditions matches

// This line is executed after the if-else block

Looping (loop, break)

loop
  // This line is executed as long as "break loop" has not occurred.
  // Indentation indicates which lines are within the loop.

  // The loop breaks conditionally.
  // If there are nested loops, break only affects the innermost loop.
  if x
    break loop

Wait for events

// Wait for one of events to occur first
wait for one of
  recv x
    // This line is executed if "recv x" occurs first
  recv y
    // This line is executed if "recv y" occurs first
  recv z

// Because there is no indented line after the event "recv z",
// this causes the execution to jump here.
// Still, even the other events will eventually lead here.

Quitting (quit)

// To quit execution, say:
quit

Functions

Functions are defined as follows:

function my_function()

  // This is some code within the function.
  // The indentation indicates which lines belong to the function.

The function above is called as follows:

my_function()