MetaFun - Pragma ADE

pickup pencircle scaled 2pt ;
draw (0,0)--(0,1)--(1,1) scaled 1cm withcolor .625 red ;
draw ((0,0)--(0,1)--(1,1)) scaled 2cm withcolor .625 yellow ;
The scaled operates on the previous expression which in the first case is the point (1,1) and in
the second case the whole path.
pickup pencircle scaled 2pt ;
draw (0,0)--(0,1)--(1,1)--cycle scaled 1cm withcolor .625 red ;
draw ((0,0)--(0,1)--(1,1)--cycle) scaled 2cm withcolor .625 yellow ;
Here the last element in the first case is not the cycle, and the next alternative does not help us
much in discovering what is going on. (Well, at least something is going on, because the result
seems to have some dimensions.)
pickup pencircle scaled 2pt ;
draw (1,1)--cycle scaled 1cm withcolor .625 red ;
draw ((1,1)--cycle) scaled 1cm withcolor .625 yellow ;
The next lines demonstrate that we're dealing with the dark sides of METAPOST, and from that we
may conclude that in case of doubt it's best to add parenthesis when such fuzzy situations threaten
to occur.
pickup pencircle scaled 2pt ;
draw (0,1)--(1,1)--cycle scaled 1cm withcolor .625 red ;
draw ((0,1)--(1,1)--cycle) scaled 1cm withcolor .625 yellow ;
Pitfalls A few more details
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