Hi, I'm new to Nim-lang.
I wanted to convert a Python script to Nim to improve my understanding of Nim.
I have the following Python code:
# Python codes:
def cross(A, B):
"""Cross product of elements in A and elements in B."""
return [a+b for a in A for b in B]
digits = '123456789'
rows = 'ABCDEFGHI'
cols = digits
squares = cross(rows, cols)
I tried to convert to Nim code but failed:
# Nim codes:
proc cross(A: string, B: string): string =
## Cross product of elements in A and elements in B.
result = string:
for a in A:
for b in B:
a&b
let digits = "123456789"
let rows = "ABCDEFGHI"
let cols = digits
var squares = cross(rows, cols)
Please help to explain how to convert the nested list comprehension. Thanks in advance.
There are few problems with your Nim version, e.g. returning string instead of seq[string] (cause this is what the Python version does - it returns a list).
Here is a correct Nim version:
proc cross(xs, ys: string): seq[string] =
## Cross product of elements in A and elements in B.
for x in xs:
for y in ys:
result.add x&y
Some more codes...
# Python codes:
unitlist = ([cross(rows, c) for c in cols] +
[cross(r, cols) for r in rows] +
[cross(rs, cs) for rs in ('ABC','DEF','GHI') for cs in ('123','456','789')])
units = dict((s, [u for u in unitlist if s in u])
for s in squares)
peers = dict((s, set(sum(units[s],[]))-set([s]))
for s in squares)
I tried with...
# Nim codes:
var unitlist: seq[string] =
[for c in cols: cross(rows, cast[string](c))] +
[for r in rows: cross(r, cols)] +
[for rs in ("ABC","DEF","GHI"):
for cs in ("123","456","789"):
cross(rs, cs)]
var units = initTable[string](4):
for s in squares:
for u in unitlist:
if s in u:
{s, u}
var peers = initTable[string](4):
for s in squares:
{s, toHashSet(sum(units[s],[]))-toHashSet([s])
The documentation of Seq & Tables are very poor in Nim. Not many examples to learn from.
Please help!
The documentation of Seq & Tables are very poor in Nim. Not many examples to learn from.
If something has a solid documentation and lots of examples, then it is tables module. :rolleyes:
I tried with...
[invalid syntax]
If you really want to force list comprehensions, how about you first get familiar with the correct Nim syntax for them? link
But my advice would be: don't use list comprehensions in Nim — think about how would you have written your python code without them and then try to translate that version, you'll have much better time.
how about you first get familiar with the correct Nim syntax for them? link
Wait, you are linking against the deprecated lc syntax.
I believe the closest non-deprecated solution is https://github.com/alehander92/comprehension ?
Thanks!
Just a clarification, why your codes have the brackets around the y loop, and not around the result.add?
cross(xs, ys: string): seq[string] =
for x in xs: (for y in ys: result.add x & y)While @trtt has it around the result.add?
cross(a, b: string): seq[string] =
for ac in a:
for bc in b:
result.add(ac & bc)This is some of the syntax that confuse me.
Expected results...
# Python output:
unitlist = [['A1', 'B1', 'C1', 'D1', 'E1', 'F1', 'G1', 'H1', 'I1'],
['A2', 'B2', 'C2', 'D2', 'E2', 'F2', 'G2', 'H2', 'I2'],
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xpected results...
# Python output:
unitlist = [['A1', 'B1', 'C1', 'D1', 'E1', 'F1', 'G1', 'H1', 'I1'],
['A2', 'B2', 'C2', 'D2', 'E2', 'F2', 'G2', 'H2', 'I2'],
['A3', 'B3', 'C3', 'D3', 'E3', 'F3', 'G3', 'H3', 'I3'], ['A4', 'B4', 'C4', 'D4', 'E4', 'F4', 'G4', 'H4', 'I4'], ['A5', 'B5', 'C5', 'D5', 'E5', 'F5', 'G5', 'H5', 'I5'], ['A6', 'B6', 'C6', 'D6', 'E6', 'F6', 'G6', 'H6', 'I6'], ['A7', 'B7', 'C7', 'D7', 'E7', 'F7', 'G7', 'H7', 'I7'], ['A8', 'B8', 'C8', 'D8', 'E8', 'F8', 'G8', 'H8', 'I8'], ['A9', 'B9', 'C9', 'D9', 'E9', 'F9', 'G9', 'H9', 'I9'], ['A1', 'A2', 'A3', 'A4', 'A5', 'A6', 'A7', 'A8', 'A9'], ['B1', 'B2', 'B3', 'B4', 'B5', 'B6', 'B7', 'B8', 'B9'], ['C1', 'C2', 'C3', 'C4', 'C5', 'C6', 'C7', 'C8', 'C9'], ['D1', 'D2', 'D3', 'D4', 'D5', 'D6', 'D7', 'D8', 'D9'], ['E1', 'E2', 'E3', 'E4', 'E5', 'E6', 'E7', 'E8', 'E9'], ['F1', 'F2', 'F3', 'F4', 'F5', 'F6', 'F7', 'F8', 'F9'], ['G1', 'G2', 'G3', 'G4', 'G5', 'G6', 'G7', 'G8', 'G9'], ['H1', 'H2', 'H3', 'H4', 'H5', 'H6', 'H7', 'H8', 'H9'], ['I1', 'I2', 'I3', 'I4', 'I5', 'I6', 'I7', 'I8', 'I9'], ['A1', 'A2', 'A3', 'B1', 'B2', 'B3', 'C1', 'C2', 'C3'], ['A4', 'A5', 'A6', 'B4', 'B5', 'B6', 'C4', 'C5', 'C6'], ['A7', 'A8', 'A9', 'B7', 'B8', 'B9', 'C7', 'C8', 'C9'], ['D1', 'D2', 'D3', 'E1', 'E2', 'E3', 'F1', 'F2', 'F3'], ['D4', 'D5', 'D6', 'E4', 'E5', 'E6', 'F4', 'F5', 'F6'], ['D7', 'D8', 'D9', 'E7', 'E8', 'E9', 'F7', 'F8', 'F9'], ['G1', 'G2', 'G3', 'H1', 'H2', 'H3', 'I1', 'I2', 'I3'], ['G4', 'G5', 'G6', 'H4', 'H5', 'H6', 'I4', 'I5', 'I6'], ['G7', 'G8', 'G9', 'H7', 'H8', 'H9', 'I7', 'I8', 'I9']]You can always follow our github instructions to produce a Nim devel version.
First get Nim from github:
git clone https://github.com/nim-lang/Nim.git
cd Nim
build_all.bat