it is annoyingly complicated to change the pattern how floating point numbers are printed in the tree view
i have to define a cell data function that receives the following parameters and needs to set the objects "text" property
(#<GTK-TREE-VIEW-COLUMN {10035BA823}>
 #<GTK-CELL-RENDERER-SPIN {10035B61B3}>
 #<GTK-TREE-STORE {100CA6EE83}>
 #S(GTK:GTK-TREE-ITER
    :STAMP 133030409
    :USER-DATA 140736951843632
    :USER-DATA-2 0
    :USER-DATA-3 0))