Distance and Offset Expressions

A fairly sophisticated set of options exists for entering distances and offsets. You can enter them explicitly as values or implicitly as being between two named existing points. An offset is a relatively short distance left or right of a particular direction or line.

Syntax

In these quasi-formal syntax definitions, a defined term (outdented) is followed by its definition (indented), with alternative definitions on separate lines or separated by vertical bars. Puzzled? See the Examples.

offset-expression: offset-prefix distance-expression
distance-expression: distance; distance operator quantity
distance: quantity; implied-distance
operator: + | - | * | /
implied-distance: from-point-number , to-point-number; , to-point-number (valid if the from-point-number is already entered in an appropriate from-point field)
offset-prefix: L | R | - | + (the prefix is always required)

Examples

In the following tables, note that case doesn't matter and that spaces are not required. Also, assume that point 102 is at a distance of exactly 25 from point 101.

Table 1: Distance Expressions.

Expression	Distance	Explanation
`10 + 2`	12
`10/2`	5
`10-2`	8
`10*3`	30
`101, 102`	25
`101,102+6`	31
`101,102/5`	5
`, 102`	25	if `101` is already in an appropriate from-point field
`, 102 -5`	20	if `101` is already in an appropriate from-point field

Table 2: Offset Expressions.

Expression	Offset	Explanation
`L 5`	L 5
`-5`	L 5
`R6.4/2`	R 3.2
`r101, 102`	R 25
`l 101,102/2`	L 12.5
`r , 102`	R 25	if `101` is already in an appropriate from-point field
`+ , 102 / 5`	R 5	if `101` is already in an appropriate from-point field

updated: 18-Jun-2009