Coding Style

Indentation

Coco uses Python-style indentation to define code hierarchy. A colon (:) at the end of a line indicates that an indented block follows.

// Standard Block (Recommended: 4 spaces)
if x > 5:
    throw "Too much"
else:
    emit "Phew"

// One-Liner (Allowed for single statements)
if x > 5: throw "Too much"
else: emit "Phew"

Key Rules:

• Consistency: All lines in a block must use the exact same number of spaces
• Tabs vs. Spaces: A TAB counts as 1 space. To avoid errors, use spaces only and never mix tabs and spaces

Multiple lines

To improve readability, developers can write long statements in multiple lines, e.g.

function NameSupply(
    n String,
    s U256,
) -> (name String,
        supply U256):
    return(name: n,
        supply: s)

Lines may continue in the next lines whenever the statement or expression is not ended, i.e. anywhere where a space could be written. Strings can be split to multiple lines, but they can't be indented as indents are included in the string.

s = "My spl
it string" // My split string
s = "My spl
    it string" // My spl    it string

Comments

Only line comments // are supported by Coco, so multi-line comments need to have // in front of each line. // and anything after it on the same line is ignored by compiler.

// We have to put a // sign in front of
// each line in multi-line
// comment
x = 5 // this is a comment

Unit test directives

One special case of comments are unit tests directives for coco test command, so // > and // < are ignored by compiler, but used for testing.

Naming Conventions

There are no hard rules for naming endpoints/functions, variables and classes in Coco. This guide uses the following naming style:

element	case
file name	snake_case.coco
coco module name	PascalCase
package name	snake_case
endpoints/functions, classes and events	PascalCase
class methods	snake_case
variables, function arguments and return values	snake_case
state and class field names	snake_case
constants	ALL_CAPS