Function: _--
Section: symbolic_operators
C-Name: gsub1e
Prototype: &
Help: x--: set x to x-1.
Description:
 (*bptr):bptr                          --$1
 (*small):small                        --$1
 (*lg):lg                              --$1
 (*int):int:parens                     $1 = subis($1, 1)
 (*real):real:parens                   $1 = subrs($1, 1)
 (*mp):mp:parens                       $1 = mpsub($1, gen_1)
 (*pol):pol:parens                     $1 = gsubgs($1, 1)
 (*gen):gen:parens                     $1 = gsubgs($1, 1)
