115 lines
2.0 KiB
CoffeeScript
115 lines
2.0 KiB
CoffeeScript
### arctan =====================================================================
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Tags
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----
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scripting, JS, internal, treenode, general concept
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Parameters
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----------
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x
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General description
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-------------------
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Returns the inverse tangent of x.
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###
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Eval_arctan = ->
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push(cadr(p1))
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Eval()
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arctan()
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arctan = ->
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d = 0
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save()
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p1 = pop()
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if (car(p1) == symbol(TAN))
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push(cadr(p1))
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restore()
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return
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if (isdouble(p1))
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errno = 0
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d = Math.atan(p1.d)
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if (errno)
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stop("arctan function error")
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push_double(d)
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restore()
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return
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if (isZeroAtomOrTensor(p1))
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push(zero)
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restore()
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return
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if (isnegative(p1))
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push(p1)
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negate()
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arctan()
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negate()
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restore()
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return
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# arctan(sin(a) / cos(a)) ?
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if (Find(p1, symbol(SIN)) && Find(p1, symbol(COS)))
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push(p1)
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numerator()
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p2 = pop()
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push(p1)
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denominator()
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p3 = pop()
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if (car(p2) == symbol(SIN) && car(p3) == symbol(COS) && equal(cadr(p2), cadr(p3)))
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push(cadr(p2))
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restore()
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return
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# arctan(1/sqrt(3)) -> pi/6
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# second if catches the other way of saying it, sqrt(3)/3
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if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), -1, 2)) or
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(car(p1) == symbol(MULTIPLY) && equalq(car(cdr(p1)), 1,3) and car(car(cdr(cdr(p1)))) == symbol(POWER) && equaln(car(cdr(car(cdr(cdr(p1))))),3) && equalq(car(cdr(cdr(car(cdr(cdr(p1)))))), 1, 2))
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push_rational(1, 6)
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if evaluatingAsFloats
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push_double(Math.PI)
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else
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push(symbol(PI))
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multiply()
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restore()
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return
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# arctan(1) -> pi/4
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if (equaln(p1, 1))
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push_rational(1, 4)
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if evaluatingAsFloats
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push_double(Math.PI)
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else
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push(symbol(PI))
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multiply()
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restore()
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return
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# arctan(sqrt(3)) -> pi/3
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if (car(p1) == symbol(POWER) && equaln(cadr(p1), 3) && equalq(caddr(p1), 1, 2))
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push_rational(1, 3)
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if evaluatingAsFloats
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push_double(Math.PI)
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else
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push(symbol(PI))
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multiply()
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restore()
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return
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push_symbol(ARCTAN)
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push(p1)
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list(2)
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restore()
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