Basic Syntax Rules
Single-line Comment
A single-line comment starts with //, as in C#, Java and many other languages.
Examples:
// This is a single-line comment i = 0 // a comment can be appended after an instruction
Multi-line Comment
A multi-line comment begins on a line that starts with /// and ends on a line that starts with .///
Multi-line comments can be nested. This is useful if you want to comment a block of code that contains already a multi-line comment.
Example:
///
this is a multi-line comment that contains
another nested multi-line comment
/// this is a nested
multi-line comment
.///
.///
Line Termination
A PPL instruction ends at the end of the source code line (i.e. at the CR or LF character). PPL instructions don’t end with a semicolon (;) as in some other languages.
Example:
i = 0 j = 1
Line Continuation
PPL uses a backslash (\) as line continuation character.
Example:
const albert = customer.create ( \
identifier = 100 \
name = "Albert" \
city = "Bern" )
The backslash at the end of line is optional whenever the number of open brackets ((, [ or <) doesn’t match the number of closed brackets (), ] or >). Hence the \ in the above code can be omitted:
const albert = customer.create (
identifier = 100
name = "Albert"
city = "Bern" )
Case Sensitivity
PPL is case-sensitive.
The following identifiers are all distinct:
happy Happy HAPPY
Identifiers
PPL identifiers start with a letter, followed by any number of letters, digits and underscores (_).
Examples:
color last_name make_delicious_coffee index_1 URI XML_file_20
In idiomatic PPL code, an underscore (_) is used to separate words in identifiers. PPL doesn’t use camel-case. Instead of …
thisIsARatherLongIdentifier
... you will see this in PPL:
this_is_a_rather_long_identifier
An identifier can optionally be prefixed to explicitly document which kind of identifier is used. For example, to make it clear that customer is an input argument (and not a constant or variable or anything else) you can write i_customer instead of customer, as shown below:
const name = i_customer.name
Prefixes are optional most of the time. They are required in rare cases where an ambiguity exists. They are sometimes useful to make the code more readable.
In some languages, identifiers start with an uppercase letter to denote a special kind of identifier. In Java, for example, variable names start with a lowercase letter and class names start with an uppercase letter. There is no such rule in PPL. Uppercase letters are used the same way they are used in the English language. For example, acronyms are written with uppercase letters:
HTML_to_PDF_converter
Code Blocks and Indents
In PPL, code embedded within a block is indented (preferably by four spaces), and the block is terminated by a dot (.) on a single line. PPL doesn’t use opening and closing curly brackets ({ and }).
Hence, code like this in a language that uses brackets …
foo {
// body
}
... is written like this in PPL:
foo
// body
.
Example:
repeat for each name in ["Alice", "Bob", "Tim", "Tom"]
if name.starts_with ( "T" ) then
write_line ( name )
.
.