| 1 | # 'sum' function
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| 2 |
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| 3 | #define A p3
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| 4 | #define B p4
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| 5 | #define I p5
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| 6 | #define X p6
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| 7 |
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| 8 | # leaves the sum at the top of the stack
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| 9 |
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| 10 | Eval_sum = ->
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| 11 | i = 0
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| 12 | j = 0
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| 13 | k = 0
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| 14 |
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| 15 |
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| 16 | # 1st arg
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| 17 | body = cadr(p1)
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| 18 |
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| 19 | # 2nd arg (index)
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| 20 | indexVariable = caddr(p1)
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| 21 | if (!issymbol(p6))
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| 22 | stop("sum: 1st arg?")
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| 23 |
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| 24 | # 3rd arg (lower limit)
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| 25 | push(cadddr(p1))
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| 26 | Eval()
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| 27 | j = pop_integer()
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| 28 | if (isNaN(j))
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| 29 | push p1
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| 30 | return
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| 31 |
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| 32 | # 4th arg (upper limit)
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| 33 | push(caddddr(p1))
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| 34 | Eval()
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| 35 | k = pop_integer()
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| 36 | if (isNaN(k))
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| 37 | push p1
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| 38 | return
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| 39 |
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| 40 |
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| 41 | # remember contents of the index
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| 42 | # variable so we can put it back after the loop
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| 43 | p4 = get_binding(indexVariable)
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| 44 |
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| 45 | push_integer(0)
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| 46 |
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| 47 | for i in [j..k]
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| 48 | push_integer(i)
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| 49 | p5 = pop()
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| 50 | set_binding(indexVariable, p5)
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| 51 | push(body)
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| 52 | Eval()
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| 53 | add()
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| 54 |
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| 55 | # put back the index variable to original content
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| 56 | set_binding(indexVariable, p4)
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