Column alignment algorithm
This example shows the implementation of an algorithm for text alignment across columns with different types of alignment (left, right, center) in the Julia programming language.
Introduction
The column alignment algorithm is used to format text data organized into a tabular structure. It allows you to create beautifully formatted tables where the columns are aligned relative to each other. This approach is used when outputting reports, logs, tables, and other structured data to improve readability. In this example, the input data is presented as text, where the fields are separated by a dollar symbol ($), а строки разделены символом новой строки.
Основная часть
Подготовка данных и вспомогательные функции
Исходный текст с разделителями в виде знака доллара
txt = """Given\$a\$txt\$file\$of\$many\$lines,\$where\$fields\$within\$a\$line\$
are\$delineated\$by\$a\$single\$'dollar'\$character,\$write\$a\$program
that\$aligns\$each\$column\$of\$fields\$by\$ensuring\$that\$words\$in\$each\$
column\$are\$separated\$by\$at\$least\$one\$space.
Further,\$allow\$for\$each\$word\$in\$a\$column\$to\$be\$either\$left\$
justified,\$right\$justified,\$or\$center\$justified\$within\$its\$column.""";
Функции для выравнивания текста разных типов:
# Left alignment: add spaces on the right
ljust(s, width) = s * " "^max(0, width - length(s))
# Right alignment: add spaces on the left
rjust(s, width) = " "^max(0, width - length(s)) * s
# Center alignment: add spaces on both sides
function center(s, width)
pad = width - length(s) # number of spaces to fill in
if pad <= 0 # if the text is already wider than the required width
return s # we return it as it is
else
pad2 = div(pad, 2) # number of spaces on the left (half)
# we return a string with spaces on the left and right
return " "^pad2 * s * " "^(pad - pad2)
end
end
Разбор входных данных
Разделяем текст на строки по символу новой строки \n.
Затем каждую строку разделяем по символу $ by first deleting the final $
parts = [split(rstrip(line, '$'), '$') for line in split(txt, '\n')]
# parts now contains an array of arrays of words (rows -> columns)
Determining the maximum column width
Creating an array to store the maximum width of each column
The maximum number of columns is defined as the maximum row length.
max_widths = zeros(Int, maximum(length, parts));
We go through all the rows and determine the maximum width for each column.
for line in parts
for (i, word) in enumerate(line)
# Updating the maximum width for column i
max_widths[i] = max(max_widths[i], length(word))
end
end
Add 1 to each column width to ensure at least one space between the columns.
max_widths .+= 1;
Formation and output of the result with different types of alignment
# We go through each type of alignment
for (label, justify) in (("to the left edge", ljust), ("to the right edge",rjust), ("the center",center))
# Output the header for the current alignment type
println("Alignment by ", label, ":\n")
# We go through each row of the source data
for line in parts
# We go through each word (column) in the row
for (j, word) in enumerate(line)
# Applying the alignment function to a word with a given column width
print(justify(word, max_widths[j]))
end
# Switching to a new line after the end of the data line
println()
end
# We draw a dividing line from hyphens
println("-"^sum(max_widths),"\n")
end
Conclusion
In this example, we looked at the implementation of the text column alignment algorithm in Julia. We have managed to create a program that accepts delimited text, splits it into columns, determines the required width of each column, and outputs formatted text with three types of alignment: left, right, and center. It is useful for creating readable tables and reports in text format, and also demonstrates the basics of working with text data and string formatting in Julia.
The example was developed using materials from Rosetta Code