Line references

These forms only work inside a document, since they refer to other lines. They return an error through the single-expression entry point, which has no document to refer to.

Expression	Meaning
prev	the result of the previous line
line 3	the result of line three
sum(line 1 : line 4)	the total of a span of lines
average(line 1 : line 4)	the mean of a span
total above	the total of every line above
average above	the same, averaged

A blank line or a heading acts as a boundary, so total above sums the current block rather than the whole document.