### Top-level Clauses

    (version <number>)

    (rule <rule_name> <rule_clause> ...)


<br><br>

### Rule Clauses

    (constraint <constraint_type> ...)

    (condition "<expression>")

    (layer "<layer_name>")


<br><br>

### Constraint Types

 * annular_width
 * clearance
 * courtyard_clearance
 * diff\_pair\_gap
 * diff\_pair\_uncoupled
 * disallow
 * edge_clearance
 * length
 * hole
 * hole_clearance
 * silk_clearance
 * skew
 * track_width
 * via_count


<br><br>

### Item Types

 * buried_via
 * graphic
 * hole
 * micro_via
 * pad
 * text
 * track
 * via
 * zone

<br>

### Examples

    (rule HV
       (constraint clearance (min 1.5mm))
       (condition "A.NetClass == 'HV'"))


    (rule HV
       (layer outer)
       (constraint clearance (min 1.5mm))
       (condition "A.NetClass == 'HV'"))


    (rule HV_HV
       # wider clearance between HV tracks
       (constraint clearance (min "1.5mm + 2.0mm"))
       (condition "A.NetClass == 'HV' && B.NetClass == 'HV'"))


    (rule HV_unshielded
       (constraint clearance (min 2mm))
       (condition "A.NetClass == 'HV' && !A.insideArea('Shield*')"))
<br><br>

### Notes

Version clause must be the first clause.

Rules should be ordered by specificity.  Later rules take
precedence over earlier rules; once a matching rule is found
no further rules will be checked.

Use Ctrl+/ to comment or uncomment line(s).
<br><br><br>

### Expression functions

All function parameters support simple wildcards (`*` and `?`).
<br><br>

    A.insideCourtyard('<footprint_refdes>')
True if any part of `A` lies within the given footprint's principal courtyard.
<br><br>

    A.insideFrontCourtyard('<footprint_refdes>')
True if any part of `A` lies within the given footprint's front courtyard.
<br><br>

    A.insideBackCourtyard('<footprint_refdes>')
True if any part of `A` lies within the given footprint's back courtyard.
<br><br>

    A.insideArea('<zone_name>')
True if any part of `A` lies within the given zone's outline.
<br><br>

    A.isPlated()
True if `A` has a hole which is plated.
<br><br>

    A.inDiffPair('<net_name>')
True if `A` has net that is part of the specified differential pair.
`<net_name>` is the base name of the differential pair.  For example, `inDiffPair('CLK')`
matches items in the `CLK_P` and `CLK_N` nets.
<br><br>

    AB.isCoupledDiffPair()
True if `A` and `B` are members of the same diff pair.
<br><br>

    A.memberOf('<group_name>')
True if `A` is a member of the given group. Includes nested membership.
<br><br>

    A.existsOnLayer('<layer_name>')
True if `A` exists on the given layer.  The layer name can be
either the name assigned in Board Setup > Board Editor Layers or
the canonical name (ie: `F.Cu`).

NB: this returns true if `A` is on the given layer, independently
of whether or not the rule is being evaluated for that layer.
For the latter use a `(layer "layer_name")` clause in the rule.
<br><br><br>

### More Examples

    (rule "copper keepout"
       (constraint disallow track via zone)
       (condition "A.insideArea('zone3')"))


    (rule "BGA neckdown"
       (constraint track_width (min 0.2mm) (opt 0.25mm))
       (constraint clearance (min 0.05mm) (opt 0.08mm))
       (condition "A.insideCourtyard('U3')"))


    # prevent silk over tented vias
    (rule silk_over_via
       (constraint silk_clearance (min 0.2mm))
       (condition "A.Type == '*Text' && B.Type == 'Via'"))


    (rule "Distance between Vias of Different Nets"  
        (constraint hole_to_hole (min 0.254mm))
        (condition "A.Type =='Via' && B.Type =='Via' && A.Net != B.Net"))

    (rule "Clearance between Pads of Different Nets"  
        (constraint clearance (min 3.0mm))
        (condition "A.Type =='Pad' && B.Type =='Pad' && A.Net != B.Net"))


    (rule "Via Hole to Track Clearance"  
        (constraint hole_clearance (min 0.254mm))
        (condition "A.Type =='Via' && B.Type =='Track'"))
    
    (rule "Pad to Track Clearance"  
        (constraint clearance (min 0.2mm))
        (condition "A.Type =='Pad' && B.Type =='Track'"))


    (rule "clearance-to-1mm-cutout"
        (constraint clearance (min 0.8mm))
        (condition "A.Layer=='Edge.Cuts' && A.Thickness == 1.0mm"))


    (rule "Max Drill Hole Size Mechanical"  
        (constraint hole (max 6.3mm))
        (condition "A.Pad_Type == 'NPTH, mechanical'"))
    
    (rule "Max Drill Hole Size PTH"  
        (constraint hole (max 6.35mm))
        (condition "A.Pad_Type == 'Through-hole'"))


    # Specify an optimal gap for a particular diff-pair
    (rule "dp clock gap"
        (constraint diff_pair_gap (opt "0.8mm"))
        (condition "A.inDiffPair('CLK') && AB.isCoupledDiffPair()"))

    # Specify a larger clearance around any diff-pair
    (rule "dp clearance"
        (constraint clearance (min "1.5mm"))
        (condition "A.inDiffPair('*') && !AB.isCoupledDiffPair()"))