Cells in Literate Julia

The {:cell} syntax for executable cells is not limited to just markdown files. It will work the same across other source types as well. This page illustrates this using literate Julia.

To use cells in a Julia file just add {:cell} at the end of a comment block before the code that you would like to be evaluated. Like so:

f(x) = x + 1
f(1)

2

The cells behave the same across all source types and so you will need to provide named cells to be able to share values between cells.

f(x::Integer) = x - 1
length(methods(f))

1

As we can see above the function f only has 1 method defined since it does not know about the previous cell. Below we will define another cell but use the same name as before so that we can access it’s definitions.

f(1)

0

When the resulting value is all that you care about when writing a cell use can just discard the output stream and the cell itself using a little CSS by adding a style="display: none" to the cell. For example below we use the attributes {cell=example output=false style="display: none"} to hide all but the result. The cell content below is methods(f):

methods(f)

• f(x::Integer) in Main.anonymous at string:1

Finally, we can also create types that have a show method defined for text/markdown. This allows us to embed arbitrary generated markdown within a parent document.

This text will appear in bold.

using Markdown

Inline cells are also possible. The source that produces them will not be displayed though, only the resulting value. stdout and stderr will not show either. If the resulting value can be displayed as text/markdown it’s AST will be embedded, like above with the block cells, otherwise it will appear as a text/plain wrapped in inline code. The previous text/plain was embedded in the resulting AST using an inline cell that evaluted the expression Markdown.md"`text/plain`". Values, such as 3 or π = 3.1415926535897..., will just display as inline code.