ATS currently supports four forms of comments: line comment, block comment of ML-style, block comment of C-style, and rest-of-file comment.
A line comment starts with the double slash symbol (//) and extends until the end of the current line.
A block comment of ML-style starts and closes with the tokens (* and *), respectively. Note that nested block comments of ML-style are allowed, that is, one block comment of ML-style can occur within another one of the same style.
A block comment of C-style starts and closes with the tokens /* and */, respectively. Note that block comments of C-style cannot be nested. The use of block comments of C-style is primarily in code that is supposed to be shared by ATS and C. In other cases, block comments of ML-style should be the preferred choice.
A rest-of-file comment starts with the quadruple slash symbol (////) and extends until the end of the file. Comments of this style of are primarily useful for developing or debugging programs.