Jun 15 2020
Think before you monospace

Put your programming font to the ultimate test case.

I conducted a poll on Mastodon to see if what fonts are used in programming these days.

Despite the limited sample size, the poll seemed representative of package installation statistics. After going through the replies to the poll, I discovered a web application called programming-fonts where you can try out 98 monospace fonts with syntax highlighting on the fly. However, a good test case was missing.

It is unlikely that a font would meet all features, while being aesthetic. Features include how similar characters are distinguishable and eye-candy like ligatures (which can be useful or weird).

As they say,

“Beauty lies in the eyes of the beholder.”

Here is a test case with some pseudo-code to identify common pitfalls and features. See if it fits your needs and ensure no surprises.

Test case template

Python

@test                                 # INFO: How @ gets rendered
def ultimate_monospace() -> bool:     # INFO: Ligature for arrow
    assert 1nfo != lnfo != Info       # WARN: 1, l, I should be distinguishable
    assert 0 != O                     # WARN: 0 and O should be distinguishable
    if find and ifnd:                 # WARN: Ligature for fi
        if this == 1 or that >= 2:    # INFO: Ligature for ==, >=
            return True

Octave

if (logic && oper || not ~= equals )  % INFO: Ligature for &&; WARN: for ~=
     ans = true
end

Javascript

() => { arrow_operator }              // INFO: Ligatures for arrow operator

HTML

<!-- INFO: Ligatures for HTML  -->
</> <empty> tag </empty>

Perl / Ruby / PHP

1 <=> 1                               # INFO: Ligatures for spaceship operator

Haskell

-- INFO: Ligatures for Haskell operators: ++, >>=,<<=, >=>, <=<
a ++ b

-- instead of
return x >>= f >>= g
-- simply go with
f x >>= g

-- instead of
\x -> return x >>= f >>= g
-- simply go with
f >=> g
-- or
g <=< f

Try it yourself

Here is how the above test case renders with Python syntax highlighting and Fira Code font:

Monospace font preview on programmingfonts.org

About the author

Ashwin Vishnu Mohanan, Ph.D. in Fluid mechanics