did IF exists in gnumeric 1.0.5 (Red Hat Distribution)

[frerejacque <daniel frerejacque free fr>]

Looking at the doc coming with gnumeric,
I thought that I could use the IF instruction:
The problem is very simple, the one for which spreadsheats
are often used: account reconciliation:

Given four cells:
B1,B2,B3,B4    
B1 and B2 receiving credit and debit,
B3 a current amount = A3+B1-B2 (it works)
I wanted to have in B4 the non-null cell of B1 and B2 (one only contain
a value)
so I put in B4   =IF (B1,B2,B1)
which is flagged as in error, as are
        =IF (B1==0,B2,B1) and 
        =IF (B1=0,B2,B1)

So my question :
        is the (shortly) documented IF implemented in gnumeric?
Or where is the mistake I made in the formula

Thanks

D. FREREJACQUE
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