TCL: How to convert a hex value to signed integer?

Question

This command assumes that the hex represents unsigned value:

set q 0xffffb764
set r [expr $q]
puts $r

Is there a simple way to make it treat q as representing a signed value rather than an unsigned value?

Answer 1

This is my solution:

  proc hex_to_signed {value} {
    set sign [expr {($value & 0b10000000000000000000000000000000)}]
    set mag  [expr {($value & 0b01111111111111111111111111111111)}]
    if {$sign==0} {
      set exp 0
    } else {
      set exp [expr -2**31]
    }       
    set value [expr {$exp + $mag}]
    return $value
  }