73 lines
1.5 KiB
Nim
73 lines
1.5 KiB
Nim
import math, rdstdin, strutils, tables
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type Stack = seq[float]
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proc lalign(s, x): string =
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s & repeatChar(x - s.len, ' ')
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proc opPow(s: var Stack) =
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let b = s.pop
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let a = s.pop
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s.add a.pow b
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proc opMul(s: var Stack) =
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let b = s.pop
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let a = s.pop
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s.add a * b
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proc opDiv(s: var Stack) =
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let b = s.pop
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let a = s.pop
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s.add a / b
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proc opAdd(s: var Stack) =
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let b = s.pop
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let a = s.pop
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s.add a + b
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proc opSub(s: var Stack) =
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let b = s.pop
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let a = s.pop
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s.add a - b
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proc opNum(s: var Stack, num) = s.add num
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let ops = toTable({"^": opPow,
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"*": opMul,
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"/": opDiv,
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"+": opAdd,
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"-": opSub})
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proc getInput(inp = ""): seq[string] =
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var inp = inp
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if inp.len == 0:
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inp = readLineFromStdin "Expression: "
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result = inp.strip.split
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proc rpnCalc(tokens): auto =
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var s: Stack = @[]
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result = @[@["TOKEN","ACTION","STACK"]]
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for token in tokens:
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var action = ""
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if ops.hasKey token:
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action = "Apply op to top of stack"
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ops[token](s)
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else:
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action = "Push num onto top of stack"
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s.opNum token.parseFloat
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result.add(@[token, action, s.map(proc (x: float): string = $x).join(" ")])
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let rpn = "3 4 2 * 1 5 - 2 3 ^ ^ / +"
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echo "For RPN expression: ", rpn
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let rp = rpnCalc rpn.getInput
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var maxColWidths = newSeq[int](rp[0].len)
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for i in 0 .. rp[0].high:
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for x in rp:
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maxColWidths[i] = max(maxColWidths[i], x[i].len)
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for x in rp:
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for i, y in x:
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stdout.write y.lalign(maxColWidths[i]), " "
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echo ""
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