DECLARE FUNCTION isnumeric$

LET true$ = "True"
LET false$ = "False"
LET s$ = "-152.34"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "1234.056789"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "1234.56"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "021101"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "Dog"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "Bad125"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "-0177"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "+123abcd.ef"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "54321"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "123xyz"
PRINT s$, " => "; isnumeric$(s$)
LET s$ = "xyz"
PRINT s$, " => "; isnumeric$(s$)
FUNCTION isnumeric$(s$)
    LET optchar$ = ""
    IF len(s$) = 0 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    IF pos(s$,"+") > 1 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    IF pos(s$,"-") > 1 then
       LET isnumeric$ = false$
       EXIT FUNCTION
    END IF
    LET ndex = 0
    FOR i = 1 to len(s$)
        SELECT CASE ord((s$)[i:i+1-1][1:1])
        CASE 43                   !+
        CASE 45                   !-
        CASE 46                   !.
             IF ndex = 1 then
                LET isnumeric$ = false$
                EXIT FUNCTION
             END IF
             LET ndex = 1
        CASE 48 to 57             !0 a 9
        CASE else
             IF pos(optchar$,((s$)[i:i+1-1])) = 0 then
                LET isnumeric$ = false$
                EXIT FUNCTION
             END IF
        END SELECT
    NEXT i
    LET isnumeric$ = true$
END FUNCTION
END