[metapost] The numbersystem internal.

Daniel H. Luecking luecking at uark.edu
Wed Jan 15 21:49:14 CET 2014

Three things:

1. At the (windows 7) command line one can activate double precision in 
metapost with
    mpost -numbersystem="double" file
    mpost -s numbersystem="double" file
produces a warning and the "scaled" value is assigned. It seems it 
needs to be
    mpost -s numbersystem=\"double\"
Windows normally lets a program do its own processing of double 
quotes, and it seems curious (to me) that mpost handles them 
differently in the two cases. I suppose the reason is obvious to 
experienced programmers...

2. Changing the value of the string numbersystem within a file has 
no effect (on the number system), but metapost will not complain and 
will in fact change the value. This renders a test like
    if numbersystem="double": <stuff for double> 
    else: <stuff for scaled> 
potentially invalid. I realize that the test 
    if 3.14159=3.141592: <stuff for scaled> 
    else: <stuff for double> 
can be used, but that leads me to the third point:

3. What are the number systems "binary" and "decimal" mentioned in
mpost --help? Are they just other names for "double"? They seem to 
have the same effect in some (very simple) tests.


Daniel H. Luecking
Department of Mathematical Sciences
University of Arkansas
Fayetteville, Arkansas

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