m4: Incr

1 
1 12.1 Decrement and increment operators
1 ======================================
1 
1 Increment and decrement of integers are supported using the builtins
1 'incr' and 'decr':
1 
1  -- Builtin: incr (NUMBER)
1  -- Builtin: decr (NUMBER)
1      Expand to the numerical value of NUMBER, incremented or
1      decremented, respectively, by one.  Except for the empty string,
1      the expansion is empty if NUMBER could not be parsed.
1 
1      The macros 'incr' and 'decr' are recognized only with parameters.
1 
1      incr(`4')
1      =>5
1      decr(`7')
1      =>6
1      incr()
1      error->m4:stdin:3: empty string treated as 0 in builtin `incr'
1      =>1
1      decr()
1      error->m4:stdin:4: empty string treated as 0 in builtin `decr'
1      =>-1
1