| 1 | # Tangent function of numerical and symbolic arguments
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| 2 |
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| 3 |
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| 4 |
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| 5 | Eval_tan = ->
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| 6 | push(cadr(p1))
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| 7 | Eval()
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| 8 | tangent()
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| 9 |
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| 10 | tangent = ->
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| 11 | save()
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| 12 | yytangent()
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| 13 | restore()
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| 14 |
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| 15 | yytangent = ->
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| 16 | n = 0
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| 17 | d = 0.0
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| 18 |
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| 19 | p1 = pop()
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| 20 |
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| 21 | if (car(p1) == symbol(ARCTAN))
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| 22 | push(cadr(p1))
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| 23 | return
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| 24 |
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| 25 | if (isdouble(p1))
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| 26 | d = Math.tan(p1.d)
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| 27 | if (Math.abs(d) < 1e-10)
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| 28 | d = 0.0
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| 29 | push_double(d)
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| 30 | return
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| 31 |
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| 32 | # tan function is antisymmetric, tan(-x) = -tan(x)
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| 33 |
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| 34 | if (isnegative(p1))
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| 35 | push(p1)
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| 36 | negate()
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| 37 | tangent()
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| 38 | negate()
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| 39 | return
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| 40 |
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| 41 | # multiply by 180/pi to go from radians to degrees.
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| 42 | # we go from radians to degrees because it's much
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| 43 | # easier to calculate symbolic results of most (not all) "classic"
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| 44 | # angles (e.g. 30,45,60...) if we calculate the degrees
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| 45 | # and the we do a switch on that.
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| 46 | # Alternatively, we could look at the fraction of pi
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| 47 | # (e.g. 60 degrees is 1/3 pi) but that's more
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| 48 | # convoluted as we'd need to look at both numerator and
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| 49 | # denominator.
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| 50 |
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| 51 | push(p1)
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| 52 | push_integer(180)
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| 53 | multiply()
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| 54 | if evaluatingAsFloats
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| 55 | push_double(Math.PI)
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| 56 | else
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| 57 | push_symbol(PI)
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| 58 | divide()
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| 59 |
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| 60 | n = pop_integer()
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| 61 |
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| 62 | # most "good" (i.e. compact) trigonometric results
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| 63 | # happen for a round number of degrees. There are some exceptions
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| 64 | # though, e.g. 22.5 degrees, which we don't capture here.
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| 65 | if (n < 0 || isNaN(n))
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| 66 | push(symbol(TAN))
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| 67 | push(p1)
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| 68 | list(2)
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| 69 | return
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| 70 |
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| 71 | switch (n % 360)
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| 72 | when 0, 180
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| 73 | push_integer(0)
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| 74 | when 30, 210
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| 75 | push_rational(1, 3)
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| 76 | push_integer(3)
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| 77 | push_rational(1, 2)
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| 78 | power()
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| 79 | multiply()
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| 80 | when 150, 330
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| 81 | push_rational(-1, 3)
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| 82 | push_integer(3)
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| 83 | push_rational(1, 2)
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| 84 | power()
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| 85 | multiply()
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| 86 | when 45, 225
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| 87 | push_integer(1)
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| 88 | when 135, 315
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| 89 | push_integer(-1)
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| 90 | when 60, 240
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| 91 | push_integer(3)
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| 92 | push_rational(1, 2)
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| 93 | power()
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| 94 | when 120, 300
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| 95 | push_integer(3)
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| 96 | push_rational(1, 2)
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| 97 | power()
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| 98 | negate()
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| 99 | else
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| 100 | push(symbol(TAN))
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| 101 | push(p1)
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| 102 | list(2)
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| 103 |
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| 104 |
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