Concatenate left-to-right (LTR) and right-to-left (RTL) text

Question

It seems that combining left-to-right (LTR) and right-to-left (RTL) text using paste can produce unexpected results for the resulting order:

(x = paste(c('green', 'أحمر', 'أزرق'), collapse=' ')) # arabic for blue and red
#> [1] "green أحمر أزرق"
paste(x, 'yellow')
#> [1] "green أحمر أزرق yellow"
paste(x, 123)
#> [1] "green أحمر أزرق 123"

Is there any known solution to this - i.e. a way to ensure concatenation in the same sequence as the arguments are given? Perhaps the answer is don't concatenate different alphabets!

Answer 1

You may use the Unicode control characters 'left-to-right embedding', u202A ("Treat the following text as embedded left-to-right"):

paste(x, "\u202A", 123)
# [1] "green أحمر أزرق ‭ 123"

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See also Terminating Explicit Directional Embeddings and Overrides, (u202C), a thorough description on UNICODE BIDIRECTIONAL ALGORITHM, and here.