Bill Allombert on Fri, 08 Mar 2013 00:41:55 +0100

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PARI 2.6 syntax 2: [f(x)|x<-a,b(x)]

Dear PARI developers,

In PARI 2.6 I introduced the following syntax:
[f(x)|x<-V] and

for example [x^2|x<-[1..100],isprime(x)]
returns the list of the square of the prime number less than 100.

The symbol <- was chosen because it was similar to Haskell syntax, and
looked similar to both 'element of' â and to a left arrow â, so it 
accomodates both mathematicians and computer scientists faith.

Unfortunately the choice of the symbol <- is problematic because
this leads to an ambiguity between x (<-) a and x < (-a), so we can
only use it immediatly after a vertical bar |, which prevents generalizing
the syntax.

Karim proposes to use <~ instead which is not ambiguous since ~ is not
a valid prefix operator. Unfortunately it is ugly with some fonts where
~ is displayed at the top instead of the middle (looking  like in <Ë). Also
it is a 'dead key' on some system (but we already use it for transposition

Pascal proposed to use the euro symbol â, but people using US keyboard might
find it hard to type.

Any other suggestion ?