Write a short program in SNOBOL that calculate the sum of all even integers from 1 to 100

Question

You should use loop for multiple iterations of addition. GOTO statement and labels can be used to design a loop of your requirement. please give me some ideas.

Answer 1

*This works on the Spitbol version of Snobol.

loop m = le(n, 98) (n = n + 2) + m :s(loop); output = m ;end

Answer 2

I think it's not really Snobol if it doesn't contain a pattern match...

This solution generates the even numbers 000 .. 100 by matching a pattern against the string "01012345678902468" and adding the generated numbers through the function add(). Looping is done through the FAIL keyword at the end of the pattern, which forces the pattern scanning to continue looking for alternatives until the expression (*EQ(h t o,100) ABORT) causes the scanning to abort.

    &FULLSCAN = 1
    DEFINE('add(x)') :(add.End);add sum = sum + x :(RETURN);add.End
    "01012345678902468" (LEN(1) $ h *LEN(1 - h)) ARB (LEN(1) $ t 
.       *LEN(9 - t)) ARB LEN(1) $ o *add(h t o) 
.       (*EQ(h t o,100) ABORT) FAIL
    OUTPUT = sum
END

Works both in Snobol and Spitbol (&FULLSCAN = 1 is needed for Snobol, it's a no-op in Spitbol)