when I type 'gap4', the result is just like this: 
couldn't read file "/home/soft/staden/staden-linux-x86-1-7-0/lib/iwidgets/iwidgets.tcl": no such file or directory
    while executing
"source $env(STADLIB)/iwidgets/iwidgets.tcl"
    (file "/home/soft/staden/staden-linux-x86-1-7-0/tables/iwidgetsrc" line 15)
    invoked from within
"source /home/soft/staden/staden-linux-x86-1-7-0/tables/iwidgetsrc"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 [list source $i]"
    (procedure "SetDefaults" line 42)
    invoked from within
"SetDefaults $tdir ${name}rc ${name}_defs"
    (procedure "simple_load_package" line 35)
    invoked from within
"simple_load_package $tcldir"
    (procedure "load_package" line 5)
    invoked from within
"load_package iwidgets"
    invoked from within
"if {[info commands tk] != ""} {
   load_package iwidgets
}"
    (file "/home/soft/staden/staden-linux-x86-1-7-0/tables/gaprc" line 6)
    invoked from within
"source /home/soft/staden/staden-linux-x86-1-7-0/tables/gaprc"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 [list source $i]"
    (procedure "SetDefaults" line 42)
    invoked from within
"SetDefaults $tdir ${name}rc ${name}_defs"
    (procedure "simple_load_package" line 35)
    invoked from within
"simple_load_package $tcldir"
    (procedure "load_package" line 5)
    invoked from within
"load_package gap"
    (file "/home/soft/staden/staden-linux-x86-1-7-0/lib/gap/gap.tcl" line 503)