The Semicolon Wars
Every programmer knows there is one true programming language. A new one every week
The remarkably wide range of programming languages would seem to offer something for everyone. We could celebrate diversity. We could let a thousand flowers bloom. What actually happens, more often, is that we launch a crusade to convert the infidels—or else exterminate them.
In 1975 Edsger W. Dijkstra, a major figure in the structured-programming movement, wrote a memo titled "How Do We Tell Truths that Might Hurt?" The "truths" were mostly Dijkstra's opinions of programming languages; how he told them was very bluntly. Fortran is "an infantile disorder," PL/I "a fatal disease," APL "a mistake, carried through to perfection." Students exposed to COBOL "are mentally mutilated beyond hope of regeneration," he said. "The use of COBOL cripples the mind; its teaching should, therefore, be regarded as a criminal offense." When the memo was published a few years later, defenders of COBOL and BASIC replied in kind, although none of them were quite able to match Dijkstra's acid rhetoric.
In fairness, I should note that most disputes over programming languages are neither as vicious nor as humorless as the affair of Dijkstra's "truths." Today's missionaries take an upbeat approach, spending more time in promoting their own religion and less in dissing the other person's beliefs. The message is no longer "You'll burn in hell if you write C." It's "Look what a paradise Python offers you!" (I think maybe I liked the old sermons better.)
Much of this proselytizing is done with the best of intentions. When you have found a tool that seems artful and elegant, you want to spread the good news. This is a generous impulse. But there is also self-interest at work. For programming language P to prosper, it must have a community of users—people who write P programs and buy books about P, who teach P to students, who agitate to get P supported on new platforms, who hire P programmers. Every convert to P improves P's chance of survival; if the convert comes from the rival language Q, so much the better.
Quarrels over notation are hardly unique to the world of computing. In mathematics there was the famous impasse between the Leibnizian dx/dt and the Newtonian "x-dot" (known as the war between deity and dotage). Chemists wrangle about how to name molecules. Even chess players have fought over how to record moves. But the situation in computer science is of a different order. Calculus never had 2,500 ways to write a derivative.
Over the years, the cacophony of programming languages has repeatedly been cited as a threat to further progress in computing. The usual response has been—what else?—to propose yet another programming language. "If we could all just get together and agree on one last, greatest language...." In the 1960s this was the ambition of PL/I, the language that Dijkstra called a fatal disease. Later, Ada was to reunify all of computing—by mandate of the U.S. Department of Defense. A decade ago Java was the shining hope, promoted with the slogan "Write once, run anywhere."
A few programming languages—most notably Fortran and Lisp—seem to be all but immortal; the rest are like waves washing ashore and then draining into the sand. Riding the crest of the latest wave are the scripting languages, especially Python and Ruby. Their origins are humble. The idea of scripting began with batch-command languages, used as "glue" to bind together other programs, and with extension languages, meant to be embedded inside programs. But scripting languages have grown up into general-purpose programming languages. They are popular now for writing Internet applications. Python also has a following in scientific computing.