#!/usr/bin/env elvish

use path

if (not-eq (count $args) 1) {
    echo "Usage: "(path:base (src)[name])" <input file>" >&2
    exit 1
}

var numbers = [(from-lines < $args[0])]

var TARGET = 2020

# Look for pairs of numbers that add to TARGET.
# Then, print the product of those two numbers.

for i [(range (count $numbers))] {
    var a = $numbers[$i]
    for b $numbers[(+ 1 $i)..] {
        if (== (+ $a $b) $TARGET) {
            echo (* $a $b)
        }
    }
}

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panic: interface conversion: interface {} is nil, not vector.node

goroutine 14909 [running]:
github.com/xiaq/persistent/vector.newIteratorWithRange(0xc0000a4c60, 0x40, 0x41, 0x7e6320)
	github.com/xiaq/persistent@v0.0.0-20200820214153-3175cfb92e14/vector/vector.go:357 +0x2f4
github.com/xiaq/persistent/vector.(*subVector).Iterator(0xc000452560, 0x759740, 0xc000452560)
	github.com/xiaq/persistent@v0.0.0-20200820214153-3175cfb92e14/vector/vector.go:322 +0x45
src.elv.sh/pkg/eval/vals.Iterate(0x759740, 0xc000452560, 0xc00041a5c0, 0x0, 0x0)
	src.elv.sh/pkg/eval/vals/iterate.go:39 +0x164
src.elv.sh/pkg/eval.(*forOp).exec(0xc0001d2000, 0xc000421b90, 0xc00019b530, 0x77f749)
	src.elv.sh/pkg/eval/builtin_special.go:595 +0x2fe
src.elv.sh/pkg/eval.(*formOp).exec(0xc0001b7ce0, 0xc000421b90, 0x0, 0x0)
	src.elv.sh/pkg/eval/compile_effect.go:332 +0xf15
src.elv.sh/pkg/eval.(*pipelineOp).exec.func1(0x7dcc00, 0xc0001b7ce0, 0xc000421b90, 0xc000208300, 0xc0003706f0, 0x0)
	src.elv.sh/pkg/eval/compile_effect.go:117 +0x3f
created by src.elv.sh/pkg/eval.(*pipelineOp).exec
	src.elv.sh/pkg/eval/compile_effect.go:116 +0x228
Exception: ./01.elv exited with 2
[tty 125], line 1: ./01.elv input.tt