Shopify/liquid — pull request #400 by boourns (2014-07-28 14:19:49+00:00)
Title: lazily create stacks

@jasonhl @csfrancis what do you guys think?

preliminary benchmarking:

before:
```
~/src/liquid (lazy_stack) ➜ bx rake benchmark:run
/usr/lib/shopify-ruby/2.1.2-shopify1/bin/ruby ./performance/benchmark.rb lax
Rehearsal ------------------------------------------------
parse: 1.880000 0.010000 1.890000 ( 1.896757)
parse & run: 4.310000 0.010000 4.320000 ( 4.323054)
--------------------------------------- total: 6.210000sec

user system total real
parse: 1.780000 0.000000 1.780000 ( 1.782656)
parse & run: 4.330000 0.020000 4.350000 ( 4.362625)
```

after:
```
~/src/liquid (lazy_stack) ➜ bx rake benchmark:run
/usr/lib/shopify-ruby/2.1.2-shopify1/bin/ruby ./performance/benchmark.rb lax
Rehearsal ------------------------------------------------
parse: 1.900000 0.000000 1.900000 ( 1.907752)
parse & run: 4.160000 0.000000 4.160000 ( 4.147444)
--------------------------------------- total: 6.060000sec

user system total real
parse: 1.690000 0.000000 1.690000 ( 1.690362)
parse & run: 4.070000 0.000000 4.070000 ( 4.082147)
```