So basically I have some code like this:

a = h + 5,
b = a/2
}], {h, -10, 10}]

It works fine for a but doesn't calculate the value of b. the output for b is simply a/2, whatever I change h to has no effect on it.


Beside that the body of your With is missing, you are making a basic mistake: You assume that you can use a inside the definition braces, when you just defined a there. This does not work.

You need to nest two With constructs to do this

Manipulate[With[{a = h + 5},
  With[{b = a/2},
   {a, b}]
  ], {h, -10, 10}]

or since version 10 or so, you can use this form (which is shown in red but that is only due to the missing support of the highlighting):

 With[{a = h + 5}, {b = a/2}, {a, b}],
 {h, -10, 10}
  • $\begingroup$ I tried it and indeed it works, but where is that form of With documented? Has Wolfram committed to this? $\endgroup$ – Alan Oct 22 '16 at 3:51
  • 1
    $\begingroup$ As far as I know this is an undocumented feature. Although it is really handy, the highlighter makes it impossible to use since I cannot stand when some 20 lines of correct code are marked red :) But I thought, I let you know. $\endgroup$ – halirutan Oct 22 '16 at 4:05
  • $\begingroup$ @Alan Undocumented. See: mathematica.stackexchange.com/a/121173/121 $\endgroup$ – Mr.Wizard Oct 22 '16 at 11:52

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