| 1 | # Condense an expression by factoring common terms.
|
| 2 |
|
| 3 |
|
| 4 |
|
| 5 | Eval_condense = ->
|
| 6 | push(cadr(p1))
|
| 7 | Eval()
|
| 8 | Condense()
|
| 9 |
|
| 10 | Condense = ->
|
| 11 | prev_expanding = expanding
|
| 12 | expanding = 0
|
| 13 | save()
|
| 14 | yycondense()
|
| 15 | restore()
|
| 16 | expanding = prev_expanding
|
| 17 |
|
| 18 | yycondense = ->
|
| 19 | #expanding = 0
|
| 20 |
|
| 21 | p1 = pop()
|
| 22 |
|
| 23 | if (car(p1) != symbol(ADD))
|
| 24 | push(p1)
|
| 25 | return
|
| 26 |
|
| 27 | # get gcd of all terms
|
| 28 |
|
| 29 | p3 = cdr(p1)
|
| 30 | push(car(p3))
|
| 31 | p3 = cdr(p3)
|
| 32 | while (iscons(p3))
|
| 33 | push(car(p3))
|
| 34 | gcd()
|
| 35 | p3 = cdr(p3)
|
| 36 |
|
| 37 | #printf("condense: this is the gcd of all the terms:\n")
|
| 38 | #print(stdout, stack[tos - 1])
|
| 39 |
|
| 40 | # divide each term by gcd
|
| 41 |
|
| 42 | inverse()
|
| 43 | p2 = pop()
|
| 44 | push(zero)
|
| 45 | p3 = cdr(p1)
|
| 46 | while (iscons(p3))
|
| 47 | push(p2)
|
| 48 | push(car(p3))
|
| 49 | multiply()
|
| 50 | add()
|
| 51 | p3 = cdr(p3)
|
| 52 |
|
| 53 | # We multiplied above w/o expanding so sum factors cancelled.
|
| 54 |
|
| 55 | # Now we expand which which normalizes the result and, in some cases,
|
| 56 | # simplifies it too (see test case H).
|
| 57 |
|
| 58 | yyexpand()
|
| 59 |
|
| 60 | # multiply result by gcd
|
| 61 |
|
| 62 | push(p2)
|
| 63 | divide()
|
| 64 |
|
| 65 |
|