gforth : how to check a variable is set with arg value

Question

gforth : how to check a variable is set

I currently set a variable from command line like :

: functionname
    variable !
; 

so it gets its value from

gforth -e"5" myfile.fs 

but then I would ensure the variable is set by a default value even if user runs

gforth myfile.fs

how can I check variable is set ? (then I can give it a default value in a if statement)

Answer 1

finally I changed method for reading the parameter :

first the function is now like :

: valorise_hauteur                                                                                                                                                           
        argc @ 2 < if                           
                cr
                ." no argument using default 5 value"
                5 hauteur !
                cr
        else
                1 arg s>number drop hauteur !
        endif              
;   

and I can call the full script :

gforth myscript.fs 10

where 10 is my arg number 1 this method is more command line way to do that & permit to use a default value.