58b20109cf
import sys
import yaml
with open(sys.argv[1]) as fp:
data = fp.read()
if not data.find("---") == 0:
# no head
print("NO YAML HEAD FOUND")
sys.exit(-1)
data = data[3:]
head_end = data.find("---")
head = data[0:head_end]
data = data[head_end+3:]
metadata = yaml.safe_load(head)
cats = metadata.pop('categories', None)
if cats != None:
if type(cats) == list:
tags = cats
elif type(cats) == str:
tags = cats.split()
tags = list(map(lambda t: t.lower(), tags))
metadata["tags"] = ", ".join(tags)
new_data = f"---\n{yaml.dump(metadata, default_flow_style=False)}---{data}"
# write it
print(f"coverted: categories to tags: {tags} - {sys.argv[1]}")
with open(sys.argv[1], "w") as fp:
fp.write(new_data)
sys.exit(0)
if not metadata.get("tags", None):
metadata["tags"] = "untagged"
new_data = f"---\n{yaml.dump(metadata, default_flow_style=False)}---{data}"
print(f"untagged: {sys.argv[1]}")
# write it
with open(sys.argv[1], "w") as fp:
fp.write(new_data)
sys.exit(0)
print("No changes needed")
21 lines
701 B
Markdown
21 lines
701 B
Markdown
---
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comments: true
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date: 2015-08-22 00:28
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layout: post
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tags: haskell, recursion, fibonacci numbers
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title: Recursion
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---
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```haskell
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fibonacci :: [Integer]
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fibonacci = 1:1:(zipWith (+) fibonacci (tail fibonacci))
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```
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Above is a simple function that generates an infinite stream of fibonacci numbers. Its written in haskell.
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This is a piece of code that made me think a lot lately, it make clever use of recursion to define the stream and computes with a linear number of additions. I think its pretty damn sexy!
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## Notes:
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- Many thanks to a co-worker who helped me figure this out.
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- I hear that there are more efficient ways to compute fibonacci numbers (namley O(logn)). - should investigate this
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